Taufiq Nawaz, Liping Gu, Zhong Hu et al.

Fuels • 2024

This comprehensive review investigates the potential of cyanobacteria, particularly nitrogen-fixing strains, in addressing global challenges pertaining to plastic pollution and carbon emissions. By analyzing the distinctive characteristics of cyanobacteria, including their minimal growth requirements, high photosynthetic efficiency, and rapid growth rates, this study elucidates their crucial role in transforming carbon sequestration, biofuel generation, and biodegradable plastic production. The investigation emphasizes cyanobacteria’s efficiency in photosynthesis, positioning them as optimal candidates for cost-effective bioplastic production with minimized land usage. Furthermore, the study explores their unconventional yet promising utilization in biodiesel production, mitigating environmental concerns such as sulfur emissions and the presence of aromatic hydrocarbons. The resulting biodiesel exhibits significant combustion potential, establishing cyanobacteria as a viable option for sustainable biofuel production. Through a comprehensive assessment of both achievements and challenges encountered during the commercialization process, this review offers valuable insights into the diverse contributions of cyanobacteria. Its objective is to provide guidance to researchers, policymakers, and industries interested in harnessing bio-inspired approaches for structural and sustainable applications, thereby advancing global efforts towards environmentally conscious plastic and biofuel production.

Miriam Izzo, Margot Jacquet, Takayuki Fujiwara et al.

International Journal of Molecular Sciences • 2021

Here, we report the development of a novel photoactive biomolecular nanoarchitecture based on the genetically engineered extremophilic photosystem I (PSI) biophotocatalyst interfaced with a single layer graphene via pyrene-nitrilotriacetic acid self-assembled monolayer (SAM). For the oriented and stable immobilization of the PSI biophotocatalyst, an His 6 -tag was genetically engineered at the N -terminus of the stromal PsaD subunit of PSI, allowing for the preferential binding of this photoactive complex with its reducing side towards the graphene monolayer. This approach yielded a novel robust and ordered nanoarchitecture designed to generate an efficient direct electron transfer pathway between graphene, the metal redox center in the organic SAM and the photo-oxidized PSI biocatalyst. The nanosystem yielded an overall current output of 16.5 µA·cm -2 for the nickel- and 17.3 µA·cm -2 for the cobalt-based nanoassemblies, and was stable for at least 1 h of continuous standard illumination. The novel green nanosystem described in this work carries the high potential for future applications due to its robustness, highly ordered and simple architecture characterized by the high biophotocatalyst loading as well as simplicity of manufacturing.

Wenwen Cui, Samantha Espley, Weiguo Liang et al.

Sustainability • 2025

Microbial fuel cells (MFCs) have gained considerable attention in recent years due to their dual potential in waste treatment and clean energy production. In the field of mine tailings treatment, MFCs exhibit a unique advantage by integrating pollutant degradation with electricity generation, gradually emerging as a significant research focus. Based on 1321 relevant publications retrieved from the Web of Science Core Collection (WoSCC) from 2004 to 2024, this study employs bibliometric analysis to systematically explore the research status and future trends of MFCs in mine tailings treatment and power generation. The main research themes include (1) distinctive publication characteristics of MFC studies in the context of mine tailings treatment; (2) key information on leading countries, institutions, journals, and disciplines contributing to this field; and (3) a comprehensive summary of technological breakthroughs, emerging research hotspots, and future development directions of MFCs in mine tailings management. By thoroughly evaluating the existing body of research, this study provides valuable guidance for scholars new to the fields of MFCs and mine tailings treatment while offering insights into the technological advancements shaping the future of this domain.

Yashar Aryanfar, Humberto García Castellanos, Karrar A. Hammoodi et al.

Environmental Progress & Sustainable Energy • 2024

Abstract This article investigates the integration of circular economy methodologies and biorefinery concepts for the sustainable recovery of bio‐based products from industrial effluents, addressing the critical need for resource efficiency and environmental sustainability in the face of climate change and resource depletion. Emphasizing the valorization of industrial by‐products, the study explores innovative, eco‐friendly recovery processes within a biorefinery framework to transform waste into valuable resources such as biofuels, biochemicals, and biomaterials. Through a systematic search in various bibliographic databases and a comprehensive literature review, the study critically analyzes existing studies, identifies research gaps, and offers new perspectives on the integration of biorefinery and circular economy principles. The findings reveal that strategic integration of biorefinery processes and circular economy principles can significantly reduce environmental footprints and foster sustainable industrial practices. Key challenges such as feedstock variability, technological barriers, and economic scalability are identified, along with recommendations for overcoming these obstacles through interdisciplinary collaboration, technological innovation, and supportive policy interventions. The main contribution of this research lies in its comprehensive approach, integrating cutting‐edge technologies and circular economy principles to offer viable strategies for sustainable bio‐based product recovery, thus significantly advancing the field of industrial sustainability. The article contributes to the advancement of sustainable technologies, policies, and strategies, advocating for a transition towards a more circular, resource‐efficient industrial sector. Continued innovation and research are emphasized to optimize recovery processes and explore new applications, supporting a sustainable and thriving future for our planet.

Patrick Jung, Felix Harion, Shujie Wu et al.

Frontiers in Astronomy and Space Sciences • 2023

Subterranean environments on Earth serve as an analog for the study of microbes on other planets, which has become an active area of research. Although it might sound contradictory that photosynthetic cyanobacteria thrive in extreme low light environments, they are frequent inhabitants of caves on Earth. Throughout the phylum these cyanobacteria have developed unique adaptations that cannot only be used for biotechnological processes but also have implications for astrobiology. They can, for example, both accommodate for the low light conditions by producing specific pigments that allow photosynthesis in near-infrared (IR) radiation/far-red light, and they can synthesize bioplastic compounds and calcium carbonate sheaths which represent valuable resources during human colonization of other planets or rock bodies. This article will highlight the potential benefits of cave-inhabiting cyanobacteria and will present a suitable bioreactor technique for the utilization of these special microbes during future space missions.

Biljana Macura, Mikołaj Piniewski, Marta Księżniak et al.

Environmental Evidence • 2019

Abstract Background Agriculture is the main sector responsible for nutrient emissions in the Baltic Sea Region and there is a growing pressure to identify cost-effective solutions towards reducing nitrogen and phosphorus loads originating from farming activities. Recycling resources from agricultural waste is central to the idea of a circular economy, and has the potential to address the most urgent problems related to nutrients use in the food chain, such as depletion of natural phosphorus reserves, water pollution and waste management. This systematic map examined what evidence exists relating to the effectiveness of ecotechnologies in agriculture for the recovery and reuse of carbon and/or nutrients (nitrogen and phosphorus) in the Baltic Sea region and other comparable boreo-temperate systems. Methods We searched for both academic and grey literature. English language searches were performed in 5 bibliographic databases and search platforms, and Google Scholar. Searches in 36 specialist websites were performed in English, Finnish, Polish and Swedish. The searches were restricted to the period 2013 to 2017. Eligibility screening was conducted at two levels: title and abstract (screened concurrently for efficiency) and full text. Meta-data was extracted from eligible studies including bibliographic details, study location, ecotechnology name and description, type of outcome (i.e. recovered or reused carbon and/or nutrients), type of ecotechnology in terms of recovery source, and type of reuse (in terms of the end-product). Findings are presented here narratively and in a searchable database, and are also visualised in a web-based evidence atlas (an interactive geographical information system). In addition, knowledge gaps and clusters have been identified in the evidence base and described in detail. Results We found 173 articles studying the effectiveness of 177 ecotechnologies. The majority of eligible articles were in English, originated from bibliographic databases and were published in 2016. Most studies with reported locations, and given our boreo-temperate scope, were conducted in Europe and North America. The three most prevalent ecotechnologies in the evidence base (collectively 40.7%) were; soil amendments, anaerobic digestion and (vermi)composting. Manure was the principal waste source used for recovery of nutrients or carbon, making up 55.4% of the all studies in evidence base, followed by a combination of manure and crop residues (22%). There were 51 studies with 14 ecotechnologies that reported on recovery of carbon and nutrients together, predominantly via (vermi)composting and anaerobic digestion. Only 27 studies focused on reuse of recovered nutrients and carbon through soil amendments. Conclusions This systematic map report provides an evidence base that can be useful for researchers and decision-makers in policy and practice working on transformation from linear to circular economy in the agricultural waste sector. Three potential topics for future systematic reviews are: (1) effectiveness of products recovered from different types of agricultural wastes as soil amendments or fertilizers; (2) effectiveness of anaerobic digestion as an ecotechnology used for recovery of nutrients and carbon; (3) effectiveness of composting and/or vermicomposting as ecotechnologies used for recovery of nutrients and carbon.

Erika J. Espinosa-Ortiz, Robin Gerlach, Brent Peyton et al.

Biofilm • 2023

Water is not only essential to sustain life on Earth, but also is a crucial resource for long-duration deep space exploration and habitation. Current systems in space rely on the resupply of water from Earth, however, as missions get longer and move farther away from Earth, resupply will no longer be a sustainable option. Thus, the development of regenerative reclamation water systems through which useable water can be recovered from "waste streams" ( i.e., used waters) is sorely needed to further close the loop in space life support systems. This review presents the origin and characteristics of different used waters generated in space and discusses the intrinsic challenges of developing suitable technologies to treat such streams given the unique constrains of space exploration and habitation ( e.g. , different gravity conditions, size and weight limitations, compatibility with other systems, etc. ). In this review, we discuss the potential use of biological systems, particularly biofilms, as possible alternatives or additions to current technologies for water reclamation and waste treatment in space. The fundamentals of biofilm reactors, their advantages and disadvantages, as well as different reactor configurations and their potential for use and challenges to be incorporated in self-sustaining and regenerative life support systems in long-duration space missions are also discussed. Furthermore, we discuss the possibility to recover value-added products ( e.g. , biomass, nutrients, water) from used waters and the opportunity to recycle and reuse such products as resources in other life support subsystems ( e.g., habitation, waste, air, etc .).

I. Robertson, Huijie Zhang, Erwin Reisner et al.

Chemical Science • 2024

Biohybrid systems for solar fuel production integrate artificial light-harvesting materials with biological catalysts such as microbes. In this perspective, we discuss the rational design of the abiotic-biotic interface in biohybrid systems by reviewing microbes and synthetic light-harvesting materials, as well as presenting various approaches to coupling these two components together. To maximise performance and scalability of such semi-artificial systems, we emphasise that the interfacial design requires consideration of two important aspects: attachment and electron transfer. It is our perspective that rational design of this photosensitiser-microbe interface is required for scalable solar fuel production. The design and assembly of a biohybrid with a well-defined electron transfer pathway allows mechanistic characterisation and optimisation for maximum efficiency. Introduction of additional catalysts to the system can close the redox cycle, omitting the need for sacrificial electron donors. Studies that electronically couple light-harvesters to well-defined biological entities, such as emerging photosensitiser-enzyme hybrids, provide valuable knowledge for the strategic design of whole-cell biohybrids. Exploring the interactions between light-harvesters and redox proteins can guide coupling strategies when translated into larger, more complex microbial systems.

Tonny I. Okedi, Adrian C. Fisher, Kamran Yunus

Biotechnology for Biofuels • 2020

A simple ratio for quantitatively evaluating the effects of cell morphology adaptations on electron transfer rates has been defined. Furthermore, the study points to engineering cell shape, either via environmental conditioning or genetic engineering, as a potential strategy for improving the performance of biophotovoltaic devices.

M. Spasojević, Olivera Prodanović, Pantic Nevena et al.

JOURNAL OF ENGINEERING & PROCESSING MANAGEMENT • 2019

<p>Strategies based on the enzyme application are increasingly replacing the conventional chemical procedures because of their efficiency, quicker performance and environmental protection. However, natural enzymes can rarely be used in industry since their beneficial features can not endure the industrial conditions. Additional drawbacks of natural enzymes are their inhibition by reaction products and difficulty to be removed from the reaction mixture. The most promising technique to substantially improve the enzyme properties, such as activity, pH, thermal and organic-solvent stability, reusability and storage stability, in non-natural environments is by the enzyme immobilization. In this review we summarized different techniques used to immobilize enzymes to inert carriers. A wide variety of materials of both the organic and inorganic origin was used as carriers for the enzyme immobilization. We also summarized a class of new materials where the enzyme performance was enhanced by combining different classical materials and shaping in specific forms.</p>

Wangyin Wang, Dingyi Li, Xupeng Cao et al.

Natural Sciences • 2021

Abstract Light is the prerequisite for photosynthesis. However, excess light flux higher than the light‐saturation point gives rise to photoinhibition or photodamage. To efficiently utilize the excess energy under the light saturation is a long‐standing issue of photosynthesis. Herein, we found an electron drainage channel using artificial redox shuttle as a nongenetic tool to direct excessive electron transfer from chloroplast of microalgae ( Chlorella pyrenoidosa ) to extracellular redox reactions. Guiding the excess electrons to the outside cell enhanced water oxidation activity of photosystem II by 2.6‐fold and increased the light saturation point by 7.1‐fold. Intrinsic quantum yield and electron transfer rate of photosystems (PSII and PSI) were also in response to an increased light flux, due to the liberation of the initial photoinhibition. The electrons drained from photosynthesis served as the reducing equivalents for extracellular synthesis of chemicals. This work sheds light on the nature of photosynthetic electron transportation and distribution in a light‐saturated state of microalgae through a nongenetic drainage of electron for extracellular chemical synthesis. Key points An electron drainage channel was developed using artificial redox mediator to liberate the photoinhibition of microalgal photosynthesis. Guiding the excess photosynthetic electrons to the outside cell enhanced water oxidation activity of photosystem II and increased the light saturation point. Electrons from photosynthesis with the reducing power can be used for extracellular synthesis of chemicals.

Ekaterina Skolotneva, Kseniia Tsygurina, Semyon Mareev et al.

International Journal of Molecular Sciences • 2022

It is known that ammonium has a higher permeability through anion exchange and bipolar membranes compared to K+ cation that has the same mobility in water. However, the mechanism of this high permeability is not clear enough. In this study, we develop a mathematical model based on the Nernst−Planck and Poisson’s equations for the diffusion of ammonium chloride through an anion-exchange membrane; proton-exchange reactions between ammonium, water and ammonia are taken into account. It is assumed that ammonium, chloride and OH− ions can only pass through membrane hydrophilic pores, while ammonia can also dissolve in membrane matrix fragments not containing water and diffuse through these fragments. It is found that due to the Donnan exclusion of H+ ions as coions, the pH in the membrane internal solution increases when approaching the membrane side facing distilled water. Consequently, there is a change in the principal nitrogen-atom carrier in the membrane: in the part close to the side facing the feed NH4Cl solution (pH < 8.8), it is the NH4+ cation, and in the part close to distilled water, NH3 molecules. The concentration of NH4+ reaches almost zero at a point close to the middle of the membrane cross-section, which approximately halves the effective thickness of the diffusion layer for the transport of this ion. When NH3 takes over the nitrogen transport, it only needs to pass through the other half of the membrane. Leaving the membrane, it captures an H+ ion from water, and the released OH− moves towards the membrane side facing the feed solution to meet the NH4+ ions. The comparison of the simulation with experiment shows a satisfactory agreement.

Mohamad Padri, Nittaya Boontian, Neung Teaumroong et al.

Water • 2021

Microalgae cultivation in wastewater is an emerging approach to remove its contaminants and generate microalgal biomass. This study aimed to screen and isolate potential strains in a cassava biogas effluent wastewater (CBEW) treatment system and produce algal biomass. Chlorella sorokiniana strains P21 and WB1DG were isolated from CBEW and found to grow by utilizing various carbon sources. Experiments conducted in a batch reactor using an unsterilized substrate were done to evaluate the nutrient removal and growth of isolated strains from CBEW. The results showed that C. sorokiniana P21 and WB1DG could achieve biomass accumulation of more than 2564 and 1301 mg L−1, respectively. The removal efficiencies of chemical oxygen demand (COD), total phosphorous (TP), and total inorganic nitrogen (TIN) were found up to be 63.42, 91.68, and 70.66%, respectively, in a WB1DG culture and 73.78, 92.11, and 67.33%, respectively, in a P21 culture. Harvestability of the P21 strain was examined using several coagulant–flocculants. FeCl3 was found to remove more than 90% of the cells. Nutrient removal and growth rates resulting from these indigenous strains with application of untreated CBEW support the possibility of this strain being a promising candidate to couple a CBEW treatment and algal biomass generation with minimal process adjustment.

Dipayan Samanta, Rajesh K. Sani

Methane • 2023

Methane, a potent greenhouse gas, has gained significant attention due to its environmental impact and economic potential. Chemical industries have focused on specialized catalytic systems, like zeolites, to convert methane into methanol. However, inherent limitations in selectivity, irreversibility, and pore blockages result in high costs and energy requirements, thus hindering their commercial viability and profitability. In contrast, biological methane conversion using methanotrophs has emerged as a promising alternative, offering higher conversion rates, self-renewability, improved selectivity, and economically feasible upstream processes. Nevertheless, biological methane oxidation encounters challenges including the difficulty in cultivating methanotrophs and their slow growth rates, which hinder large-scale bioprocessing. Another highlighted limitation is the limited mass transfer of methane into liquid in bioreactors. Practical strategies to enhance methane oxidation in biological systems, including optimizing reactor design to improve mass transfer, altering metal concentrations, genetic engineering of methane monooxygenases, enzyme encapsulation, and utilizing microbial consortia are discussed. By addressing the limitations of chemical approaches and highlighting the potential of biological methods, the review concluded that the utilization of genetically engineered methanotrophic biofilms on beads within a biotrickling reactor, along with enhanced aeration rates, will likely enhance methane oxidation and subsequent methane conversion rates.

Jiafeng Ding, Yunjuan Meng, Shihuan Lu et al.

Toxics • 2023

Algal cell proliferation has posed significant problems for traditional water treatment facilities; these problems are attributed to surface hydrophilicity and electrostatic repulsion. Biological aerated filters (BAFs) have been extensively used in wastewater treatment to remove pollutants such as algal cells by utilizing the adsorption and separation capabilities of the filter media. In this study, a BAF was supplemented with biological filter medium ( Marchantia polymorpha ) to assess its effectiveness of pretreating aquaculture wastewater. In terms of process performance, steady and consistent treatment was achieved by the BAF with M. polymorpha (BAF2) under an algal cell density as high as 1.65 × 10 8 cell/L, with average removal rates for NH 4 + -N and algae cells of 74.4% and 81.9%, respectively. The photosynthetic activity parameters (rETRmax, α, Fv/Fm, and I k ) of the influent and effluent were quantitatively assessed, and M. polymorpha was found to remove algae by disrupting the photosynthetic system of the algal cells. Furthermore, the addition of the M. polymorpha filter medium enhanced the community structure of the functional microbes in the BAF system. The highest microbial community richness and diversity were observed in the BAF2. Meanwhile, M. polymorpha promoted an increase in the abundance of denitrifying bacteria, including Bdellovibrio and Pseudomonas . Overall, this work offers a unique perspective on the aquaculture wastewater pretreatment process and BAF design.

Mohan Wei, Yaozhong Zhang, Yifan Wang et al.

Membranes • 2024

Membrane fouling presents a significant challenge in the treatment of wastewater. Several detection methods have been used to interpret membrane fouling processes. Compared with other analysis and detection methods, atomic force microscopy (AFM) is widely used because of its advantages in liquid-phase in situ 3D imaging, ability to measure interactive forces, and mild testing conditions. Although AFM has been widely used in the study of membrane fouling, the current literature has not fully explored its potential. This review aims to uncover and provide a new perspective on the application of AFM technology in future studies on membrane fouling. Initially, a rigorous review was conducted on the morphology, roughness, and interaction forces of AFM in situ characterization of membranes and foulants. Then, the application of AFM in the process of changing membrane fouling factors was reviewed based on its in situ measurement capability, and it was found that changes in ionic conditions, pH, voltage, and even time can cause changes in membrane fouling morphology and forces. Existing membrane fouling models are then discussed, and the role of AFM in predicting and testing these models is presented. Finally, the potential of the improved AFM techniques to be applied in the field of membrane fouling has been underestimated. In this paper, we have fully elucidated the potentials of the improved AFM techniques to be applied in the process of membrane fouling, and we have presented the current challenges and the directions for the future development in an attempt to provide new insights into this field.

Yong Jin, Kasper D. de Leeuw, David P. B. T. B. Strik

Materials • 2023

Polyhydroxyalkanoates (PHA) polymers are emerging within biobased biodegradable plastic products. To build a circular economy, effective recycling routes should be established for these and other end-of-life bioplastics. This study presents the first steps of a potential PHA recycling route by fermenting hydrolyzed PHA-based bioplastics (Tianan ENMATTM Y1000P; PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)) into carboxylates acetate and butyrate. First, three different hydrolysis pretreatment methods under acid, base, and neutral pH conditions were tested. The highest 10% (from 158.8 g COD/L to 16.3 g COD/L) of hydrolysate yield was obtained with the alkaline pretreatment. After filtration to remove the remaining solid materials, 4 g COD/L of the hydrolyzed PHA was used as the substrate with the addition of microbial nutrients for mixed culture fermentation. Due to microbial conversion, 1.71 g/L acetate and 1.20 g/L butyrate were produced. An apparent complete bioconversion from intermediates such as 3-hydroxybutyrate (3-HB) and/or crotonate into carboxylates was found. The overall yields of the combined processes were calculated as 0.07 g acetate/g PHA and 0.049 g butyrate/g PHA. These produced carboxylates can theoretically be used to reproduce PHA or serve many other applications as part of the so-called carboxylate platform.

Marco Zeppilli, Ilaria Ceccarelli, Marianna Villano et al.

IRIS Research product catalog (Sapienza University of Rome) • 2016

A microbial electrolysis cell (MEC) was operated in continuous-flow condition to obtain cathodic CO2 reduction into acetate and methane along with COD anodic oxidation. Under steady-state conditions, most of the electron equivalents produced by COD anodic oxidation (866 mgCOD/Ld) were diverted into current rather than microbial growth, with an average Coulombic efficiency of 95 ± 8 %. In the cathodic chamber, acetate and methane formation from CO2 reduction accounted for 76% of the equivalents generated in the anodic oxidation reaction. Because a spill of cathodic liquid phase was necessary in order to counterbalance osmotic diffusion across the PEM, it was also possible to spill from the cathodic chamber a concentrated stream of acetate (248 ± 16meq/L). Moreover, as an additional effect, cation transport across the proton exchange membrane (PEM) and the consequent alkalinity generation made it possible to accumulate ammoniumnitrogen (242 ± 19 mgN/L) and bicarbonate (22.49 ± 1.45 gHCO3-/L). Hence, the MEC combined COD andCO2 removal in addition to nutrients and energy recovery from an anodic influent that simulated an urban wastewater.

José Ramón Copa Rey, Cécilia Mateos-Pedrero, Andrei Longo et al.

Energies • 2024

Hydrogen is undeniably one of the most promising options for producing energy with minimal environmental impact. However, current hydrogen production is still derived from carbon-intensive processes relying on fossil fuels. Biomass is a sustainable and versatile resource that can be converted into hydrogen through biological and thermochemical pathways from a large variety of feedstocks and technologies. This work reviews and compares existing biomass-to-hydrogen technologies, focusing on their characteristics, maturity level, benefits, limitations, and techno-economic and lifecycle environmental impacts. Less-developed biological conversion methods are characterized by low efficiencies and hydrogen productivity. More mature thermochemical routes enable higher efficiencies and hydrogen yields. Overall, while thermochemical processes suit centralized large-scale hydrogen production, biological pathways offer decentralized options, necessitating continued innovation for integration into future energy strategies. Some of these technologies, such as anaerobic digestion (best-case: 1.28 EUR/kgH2) and conventional gasification (best-case: 1.79 EUR/kgH2), emerge as promising, sustainable, and affordable alternatives for renewable hydrogen generation, offering production costs comparable to those of natural gas steam reforming (0.92–2.8 EUR/kgH2).

Gabriele Soggia, Andrea Goglio, Pierangela Cristiani et al.

Renewable Energy • 2024

Microbial electrosynthesis (MES) cell use is an innovative approach for single-cell proteins (SCP) production. Coupling MES with the valorization of CO2 from anaerobic digestion and nitrogen from livestock effluents has beneficial environmental effects, reducing greenhouse gas emissions and nitrogen overloading. In addition, the reducing power needed can come from surplus renewable energy. In this study, MES with a biochar-functionalized cathode was tested at varying polarizations, i.e. non polarized, -0.6 V and -1.0 V vs Ag/AgCl, and biogas-derived CO2 and recovered ammonia from pig slurry was supplied. Negative polarization switched the microbial community from heterotrophic, typical of unpolarized MES, to a mix of both heterotrophic and autotrophic/electrotrophic communities at -0.6 V and to mainly autotrophic/electrotrophic at -1.0 V. The more negative polarization allowed the highest CO2 and N capture, i.e. 39 ± 2 % of the supplied CO2, and 6.7 ± 0.8 % supplied N. Microbial biomass characterization indicated a protein content on dry matter basis of 33.1 ± 1.3 % (unpolarized), 43.2 ± 0.6 % (-0.6 V) and 69.1 ± 1.0 % (-1.0 V). The amino acids profiles investigated showed a high nutritional value of the produced biomass, not far from those of conventional protein sources used for producing feed/food.

Maria Paula Giulianetti de Almeida, Gustavo Mockaitis, David G. Weissbrodt

Fermentation • 2023

Whey has applications in food, beverages, personal care products, pharmaceuticals, and the medical sector. However, it remains a massive dairy residue worldwide (160.7 million m3 year−1), with high organic and nutrient loads. About 42% is used for low-value products such as animal feed and fertilizers or is even directly discharged into water streams, leading to ecosystem damage via eutrophication. We reviewed the uses and applications of cheese whey, along with associated environmental impacts and innovative ways to mitigate them using affordable and scalable technologies. Recycling and repurposing whey remain challenges for remote locations and poor communities with limited access to expensive technology. We propose a closed-loop biorefinery strategy to simultaneously mitigate environmental impacts and valorize whey resources. Anaerobic digestion utilizes whey to produce biogas and/or carboxylates. Alternative processes combining anaerobic digestion and low-cost open photobioprocesses can valorize whey and capture organic, nitrogenous, and phosphorous nutrients into microalgal biomass that can be used as food and crop supply or processed into biofuels, pigments, and antioxidants, among other value-added products. The complete valorization of cheese whey also depends on facilitating access to relevant information on whey production, identifying stakeholders, reducing technology gaps among countries, enforcing legislation and compliance, and creating subsidies and fostering partnerships with industries and between countries.

Juntai Liu, Vincent M. Friebe, Raoul N. Frese et al.

Nature Communications • 2020

Natural photosynthesis can be divided between the chlorophyll-containing plants, algae and cyanobacteria that make up the oxygenic phototrophs and a diversity of bacteriochlorophyll-containing bacteria that make up the anoxygenic phototrophs. Photosynthetic light harvesting and reaction centre proteins from both kingdoms have been exploited for solar energy conversion, solar fuel synthesis and sensing technologies, but the energy harvesting abilities of these devices are limited by each protein's individual palette of pigments. In this work we demonstrate a range of genetically-encoded, self-assembling photosystems in which recombinant plant light harvesting complexes are covalently locked with reaction centres from a purple photosynthetic bacterium, producing macromolecular chimeras that display mechanisms of polychromatic solar energy harvesting and conversion. Our findings illustrate the power of a synthetic biology approach in which bottom-up construction of photosystems using naturally diverse but mechanistically complementary components can be achieved in a predictable fashion through the encoding of adaptable, plug-and-play covalent interfaces.

Gaydaa AlZohbi

ChemEngineering • 2024

The global issue of climate change caused by humans and its inextricable linkage to our present and future energy demand presents the biggest challenge facing our globe. Hydrogen has been introduced as a new renewable energy resource. It is envisaged to be a crucial vector in the vast low-carbon transition to mitigate climate change, minimize oil reliance, reinforce energy security, solve the intermittency of renewable energy resources, and ameliorate energy performance in the transportation sector by using it in energy storage, energy generation, and transport sectors. Many technologies have been developed to generate hydrogen. The current paper presents a review of the current and developing technologies to produce hydrogen from fossil fuels and alternative resources like water and biomass. The results showed that reformation and gasification are the most mature and used technologies. However, the weaknesses of these technologies include high energy consumption and high carbon emissions. Thermochemical water splitting, biohydrogen, and photo-electrolysis are long-term and clean technologies, but they require more technical development and cost reduction to implement reformation technologies efficiently and on a large scale. A combination of water electrolysis with renewable energy resources is an ecofriendly method. Since hydrogen is viewed as a considerable game-changer for future fuels, this paper also highlights the challenges facing hydrogen generation. Moreover, an economic analysis of the technologies used to generate hydrogen is carried out in this study.

Lázaro Adrián González-Fernández, Nahúm Andrés Medellín-Castillo, M. Sánchez‐Polo et al.

Processes • 2025

Water pollution from industrial, municipal, and agricultural sources is a pressing global concern, necessitating the development of sustainable and efficient treatment solutions. Algal biomass has emerged as a promising feedstock for the production of carbonaceous adsorbents due to its rapid growth, high photosynthetic efficiency, and ability to thrive in wastewater. This review examines the conversion of algal biomass into biochar and hydrochar through pyrolysis and hydrothermal processes, respectively, and evaluates their potential applications in wastewater treatment, carbon sequestration, and biofuel production. Pyrolyzed algal biochars typically exhibit a moderate to high carbon content and a porous structure but require activation treatments (e.g., KOH or ZnCl2) to enhance their surface area and adsorption capabilities. Hydrothermal carbonization, conducted at lower temperatures (180–260 °C), produces hydrochars rich in oxygenated functional groups with enhanced cation exchange capacities, making them effective for pollutant removal. Algal-derived biochars and hydrochars have been successfully applied for the adsorption of heavy metals, dyes, and pharmaceutical contaminants, with adsorption capacities significantly increasing through post-treatment modifications. Beyond wastewater treatment, algal biochars serve as effective carbon sequestration materials due to their stable structure and high carbon retention. Their application as soil amendments enhances long-term carbon storage and improves soil fertility. Additionally, algal biomass plays a key role in biofuel production, particularly for biodiesel synthesis, where microalgae’s high lipid content facilitates bio-oil generation. Hydrochars, with energy values in the range of 20–26 MJ/kg, are viable solid fuels for combustion and co-firing, supporting renewable energy generation. Furthermore, the integration of these materials into bioenergy systems allows for waste valorization, pollution control, and energy recovery, contributing to a sustainable circular economy. This review provides a comprehensive analysis of algal-derived biochars and hydrochars, emphasizing their physicochemical properties, adsorption performance, and post-treatment modifications. It explores their feasibility for large-scale wastewater remediation, carbon capture, and bioenergy applications, addressing current challenges and future research directions. By advancing the understanding of algal biomass as a multifunctional resource, this study highlights its potential for environmental sustainability and energy innovation.

Aşkın Sevinç Aslan, Jarkko Valjakka, Jouni Ruupunen et al.

Protein Engineering Design and Selection • 2016

While formate dehydrogenases (FDHs) have been used for cofactor recycling in chemoenzymatic synthesis, the ability of FDH to reduce CO 2 could also be utilized in the conversion of CO 2 to useful products via formate (HCOO - ). In this study, we investigated the reduction of CO 2 in the form of hydrogen carbonate (HCO 3 - ) to formate by FDHs from Candida methylica (CmFDH) and Chaetomium thermophilum (CtFDH) in a NADH-dependent reaction. The catalytic performance with HCO 3 - as a substrate was evaluated by measuring the kinetic rates and conducting productivity assays. CtFDH showed a higher efficiency in converting HCO 3 - to formate than CmFDH, whereas CmFDH was better in the oxidation of formate. The pH optimum of the reduction was at pH 7-8. However, the high concentrations of HCO 3 - reduced the reaction rate. CtFDH was modeled in the presence of HCO 3 - showing that it fits to the active site. The active site setting for hydride transfer in CO 2 reduction was modeled. The hydride donated by NADH would form a favorable contact to the carbon atom of HCO 3 - , resulting in a surplus of electrons within the molecule. This would cause the complex formed by hydrogen carbonate and the hydride to break into formate and hydroxide ions.

Hongbo Liu, Yicheng Lv, Suyun Xu et al.

The Science of The Total Environment • 2019

Most of the developing countries are in need of sanitary toilets due to insufficient supporting facilities and proven technology mainly on disposal of fecal sewage. A microbial fuel cell (MFC)-microbial electrolytic cell (MEC) coupling with an anaerobic baffle reactor (ABR) was used to realize simultaneous removal of nitrogen and carbon in fecal sewage and complete energy recycling. Configuration and rapid start-up of the ABR-MFC-MEC process treating fecal sewage was systematically studied. Results showed that the application of an external voltage of 0.5 V can shorten the start-up time and improve hydrogen production rate to 3.42 × 10 -3 m 3 -H 2 /m 3 /d in the MEC unit, where the double-chamber MFC can drive MEC completing the synchronous coupling start-up. In the single and double chamber systems, bio-electrochemical processes both enhanced shock resistance capacity of the whole ABR-MFC-MEC process during coupled operation, with chemical oxygen demand (COD) removal rates of 99.2% and 98.9% for the single and double chamber systems respectively. Based on results of biological analysis, the coupled system has a distinct selective effect on microbial population and each unit has high microbial diversity to enhance the stability and resistance of the whole system for treatment of feces and urine.

Rahul Prasad Singh, Priya Yadav, Indrajeet Kumar et al.

Sustainability • 2023

The world is currently facing global energy crises and escalating environmental pollution, which are caused by the extensive exploitation of conventional energy sources. The limited availability of conventional energy sources has opened the door to the search for alternative energy sources. In this regard, microalgae have emerged as a promising substitute for conventional energy sources due to their high photosynthetic rate, high carbohydrate and lipid content, efficient CO2 fixation capacity, and ability to thrive in adverse environments. The research and development of microalgal-based biofuel as a clean and sustainable alternative energy source has been ongoing for many years, but it has not yet been widely adopted commercially. However, it is currently gaining greater attention due to the integrated biorefinery concept. This study provides an in-depth review of recent advances in microalgae cultivation techniques and explores methods for increasing lipid production by manipulating environmental factors. Furthermore, our discussions have covered high lipid content microalgal species, harvesting methods, biorefinery concepts, process optimizing software tools, and the accumulation of triglycerides in lipid droplets. The study additionally explores the influence of abiotic stresses on the response of biosynthetic genes involved in lipid synthesis and metabolism. In conclusion, algae-based biofuels offer a viable alternative to traditional fuels for meeting the growing demand for energy.

Felipe Robledo‐Padilla, O. Aquines Gutierrez, Arisbe Silva-Núñez et al.

Microorganisms • 2020

Among the different chemical and physical treatments used to remove the color of the textile effluents, bioremediation offers many benefits to the environment. In this study, we determined the potential of Spirulina platensis ( S. platensis ) for decolorizing indigo blue dye under different incubation conditions. The microalgae were incubated at different pH (from 4 to 10) to calibrate for the optimal discoloration condition; a pH of 4 was found to be optimal. The biomass concentration in all experiments was 1 g/L, which was able to decolorize the indigo blue dye by day 3. These results showed that S. platensis is capable of removing indigo blue dye at low biomass. However, this was dependent on the treatment conditions, where temperature played the most crucial role. Two theoretical adsorption models, namely (1) a first-order model equation and (2) a second-order rate equation, were compared with observed adsorption vs. time curves for different initial concentrations (from 25 to 100 mg/L). The comparison between models showed similar accuracy and agreement with the experimental values. The observed adsorption isotherms for three temperatures (30, 40, and 50 °C) were plotted, showing fairly linear behavior in the measured range. The adsorption equilibrium isotherms were estimated, providing an initial description of the dye removal capacity of S. platensis .

Pedro Lozano, Eduardo Garcı́a-Verdugo

Green Chemistry • 2023

Biocatalysts raised by the green chemistry and circular chemistry principles can constitute the most important and efficient strategy for achieving many of the 17 Sustainable Development Goals launched by the UN.

Van Nhanh Nguyen, Krzysztof Rudzki, Marek Dzida et al.

Polish Maritime Research • 2023

Abstract Due to recent emission-associated regulations imposed on marine fuel, ship owners have been forced to seek alternate fuels, in order to meet the new limits. The aim of achieving low-carbon shipping by the year 2050, has meant that alternative marine fuels, as well as various technological and operational initiatives, need to be taken into account. This article evaluates and examines recent clean fuels and novel clean technologies for vessels. The alternative fuels are classified as low-carbon fuels, carbon-free fuels, and carbon neutral fuels, based on their properties. Fuel properties, the status of technological development, and existing challenges are also summarised in this paper. Furthermore, researchers have also investigated energy-saving devices and discovered that zero-carbon and virtually zero-carbon clean fuels, together with clean production, might play an important part in shipping, despite the commercial impracticability of existing costs and infrastructure. More interestingly, the transition to marine fuel is known to be a lengthy process; thus, early consensus-building, as well as action-adoption, in the maritime community is critical for meeting the expectations and aims of sustainable marine transportation.

Agnieszka A. Pilarska, Tomasz Kulupa, Adrianna Kubiak et al.

Energies • 2023

In recent years, growing environmental awareness, the need to reduce greenhouse gas emissions, and the energy crisis have led many countries to seek alternative energy sources. One of the most promising solutions is biogas production via anaerobic digestion (AD), whose substrate can be organic-rich and easily biodegradable food waste (FW). This waste is a significant part of the global waste problem, and its use for energy production is beneficial to both the environment and the economy. This paper presents important issues concerning the monitoring of the AD process, as well as standard and innovative, for the implementation of this process, technological solutions. The aim of the measures taken to optimise the process is to increase AD efficiency and obtain the highest possible methane content in biogas. Two approaches—pretreatment and anaerobic co-digestion (AcoD)—have been integral to the implementation of AD of food waste for years. They are presented in this paper based on a review of recent research developments. Pretreatment methods are discussed with particular emphasis on mechanical, chemical and biological methods. The AcoD of FW with different organic substrates has been extensively reviewed, as confirmed by numerous studies, where higher buffer capacity and optimum nutrient balance enhance the biogas/methane yields. Attention was also paid to the parameters, operating mode and configurations of anaerobic digesters, with a thorough analysis of the advantages and disadvantages of each solution. The article concludes with a brief presentation of the development perspectives for the discussed FW management method and recommendations.

Wen Yu, Haotian Bai, Yue Zeng et al.

Research • 2022

Photosynthetic biohybrid systems exhibit promising performance in biosynthesis; however, these systems can only produce a single metabolite and cannot further transform carbon sources into highly valuable chemical production. Herein, a photosynthetic biohybrid system integrating biological and chemical cascade synthesis was developed for solar-driven conversion of glucose to value-added chemicals. A new ternary cooperative biohybrid system, namely bacterial factory, was constructed by self-assembling of enzyme-modified light-harvesting donor-acceptor conjugated polymer nanoparticles (D-A CPNs) and genetically engineered Escherichia coli ( E. coli ). The D-A CPNs coating on E. coli could effectively generate electrons under light irradiation, which were transferred into E. coli to promote the 37% increment of threonine production by increasing the ratio of nicotinamide adenine dinucleotide phosphate (NADPH). Subsequently, the metabolized threonine was catalyzed by threonine deaminase covalently linking with D-A CPNs to obtain 2-oxobutyrate, which is an important precursor of drugs and chemicals. The 2-oxobutyrate yield under light irradiation is increased by 58% in comparison to that in dark. This work provides a new organic semiconductor-microorganism photosynthetic biohybrid system for biological and chemical cascade synthesis of highly valuable chemicals by taking advantage of renewable carbon sources and solar energy.

Muhammad Aamir Shahzad, Fares Almomani, Asif Shahzad et al.

Process Safety and Environmental Protection • 2024

Addressing global food security is a paramount challenge that necessitates a shift towards enhanced food self-sufficiency. The escalating demand for animal-derived proteins, such as meat and dairy, underscores the critical role of livestock farming in meeting the nutritional needs of the global population. To sustain this, protein-rich feed, essential for livestock production, consumes a considerable share of agricultural resources. Concurrently, urban expansion significantly increases organic waste, undermining both economic and environmental sustainability. This highlights the urgent need for innovative waste management solutions that bolster sustainability. Microbial protein (MP), produced by methane-oxidizing bacteria (MOB), presents a promising solution. It offers a land-independent method for producing feed for livestock and aquaculture, potentially alleviating the pressure on agricultural lands. Despite its advantages, reliance on natural gas for MP production raises sustainability concerns when compared to traditional feeds like fishmeal and soybean meal. Recent research focuses on valorizing waste materials using high-protein microorganisms for animal feed production, thereby addressing these concerns. Aerobic fermentation of methane to produce MP, utilizing methanotrophic microbes, showcases distinct advantages. These microbes produce a protein-rich biomass, containing over 75% protein, offering a viable alternative to conventional protein sources. This review explores the potential of urban biowaste valorization for MP production through the integration of anaerobic digestion (AD) and subsequent fermentation of biogas. It delves into the valorization mechanisms of biogas from AD to MP, highlighting methane's value in MP production for environmental and economic sustainability. Despite advancements, challenges such as inefficient fermenters, MOB inhibition, and safety issues hinder large-scale MP production. Further investigation into the life cycle assessment (LCA) and techno-economic analysis (TCA) of these integrated technologies is essential for enhancing and establishing a sustainable MP production system.

Michele Aresta, Angela Dibenedetto

Frontiers in Energy Research • 2020

The conversion of CO2 into added value chemicals, materials and fuels is a case of transition from the linear to the cyclic-C economy, a necessary change for stopping the putative negative effect of CO2 on climate and the environment. Several strategies can be implemented for CO2 conversion and their potential and timeframe is discussed in this perspective paper. The overall amount of avoided CO2 is evaluated in the short-, medium-, and long-term. The distinct contribution of Catalysis, Solar Chemistry and integrated Chemocatalysis-Biosystems is discussed.

Lisandra Rocha‐Meneses, Mario Luna-delRisco, Carlos E. Arrieta et al.

Energies • 2023

The escalating global energy demand, driven by heavy reliance on fossil fuels, worsens environmental degradation and triggers socio-economic shifts in extraction and refinery hubs. In Colombia, the energy matrix is predominantly fossil-based (76%), with hydroelectric power accounting for 70% of electricity generation. However, renewable energy sources only contribute 2% to the national energy mix. To reduce emissions by 20% by 2030, Colombia has presented an energy transition roadmap. The need for bioenergy production in Colombia arises from the residual biomass availability, the potential to provide sustainable energy access, and the potential to mitigate climate change impacts, while addressing energy poverty and enhancing energy security. This study presents an overview of biogas production in Colombia, emphasizing the need for financial resources to overcome barriers. Policy incentives, awareness campaigns, and research and development play a vital role in fostering social acceptance, technology adoption, and optimizing biogas production processes. Collaborative efforts among the government, private sector, and local communities are recommended to ensure wide-scale adoption of biogas, promoting economic, social, and environmental sustainability. By enabling informed decision-making, this research supports the transition to renewable energy sources and the achievement of sustainable development goals (SDGs), with a particular focus on bioenergy. The aim of this study is to explore the challenges and opportunities associated with biogas production in Colombia, including technical, economic, social, and environmental aspects, and provide recommendations for promoting its sustainable implementation and widespread adoption in the country.

Hengkai Meng, Wei Zhang, Huawei Zhu et al.

Biotechnology for Biofuels • 2021

This strategy provides a novel orthologous way to improve photosynthesis via enhancing CET and supply sufficient NADH for the photosynthetic production of chemicals.

Elif Kurt, Jiansong Qin, Alexandria Williams et al.

Bioengineering • 2023

Microbial cell factories offer an eco-friendly alternative for transforming raw materials into commercially valuable products because of their reduced carbon impact compared to conventional industrial procedures. These systems often depend on lignocellulosic feedstocks, mainly pentose and hexose sugars. One major hurdle when utilizing these sugars, especially glucose, is balancing carbon allocation to satisfy energy, cofactor, and other essential component needs for cellular proliferation while maintaining a robust yield. Nearly half or more of this carbon is inevitably lost as CO 2 during the biosynthesis of regular metabolic necessities. This loss lowers the production yield and compromises the benefit of reducing greenhouse gas emissions-a fundamental advantage of biomanufacturing. This review paper posits the perspectives of using CO 2 from the atmosphere, industrial wastes, or the exhausted gases generated in microbial fermentation as a feedstock for biomanufacturing. Achieving the carbon-neutral or -negative goals is addressed under two main strategies. The one-step strategy uses novel metabolic pathway design and engineering approaches to directly fix the CO 2 toward the synthesis of the desired products. Due to the limitation of the yield and efficiency in one-step fixation, the two-step strategy aims to integrate firstly the electrochemical conversion of the exhausted CO 2 into C 1 /C 2 products such as formate, methanol, acetate, and ethanol, and a second fermentation process to utilize the CO 2 -derived C 1 /C 2 chemicals or co-utilize C 5 /C 6 sugars and C 1 /C 2 chemicals for product formation. The potential and challenges of using CO 2 as a feedstock for future biomanufacturing of fuels and chemicals are also discussed.

Wen Yu, Yue Zeng, Zenghao Wang et al.

Science Advances • 2023

Developing artificial symbionts beyond natural synthesis limitations would bring revolutionary contributions to agriculture, medicine, environment, etc. Here, we initiated a solar-driven multi-organism symbiont, which was assembled by the CO 2 fixation module of Synechocystis sp., N 2 fixation module of Rhodopseudomonas palustris , biofunctional polypeptides synthesis module of Bacillus licheniformis , and the electron transfer module of conductive cationic poly(fluorene- co -phenylene) derivative. The modular design broke the pathway to synthesize γ-polyglutamic acid (γ-PGA) using CO 2 and N 2 , attributing to the artificially constructed direct interspecific substance and electron transfer. So, the intracellular ATP and NADPH were enhanced by 69 and 30%, respectively, and the produced γ-PGA was enhanced by 104%. The strategy was further extended to produce a commercial antibiotic of bacitracin A. These achievements improve the selectivity and yield of functional polypeptides with one click by CO 2 and N 2 , and also provide an innovative strategy for creating photosynthetic systems on demand.

Vincent M. Friebe, Raoul N. Frese

Current Opinion in Electrochemistry • 2017

K Iwai, Dang‐Trang Nguyen, Kozo Taguchi

International Journal of Chemical Engineering and Applications • 2019