RESUMEN

Biofuel can be generated by different organisms using various substrates. The green alga Chlorococcum humicola OQ934050 exhibited the capability to photosynthesize carbonate carbon, maybe via the activity of carbonic anhydrase enzymes. The optimum treatment is C:N ratio of 1:1 (0.2 mmoles sodium carbonate and 0.2 mmoles sodium nitrate) as it induced the highest dry mass (more than 0.5 mg.mL-1). At this combination, biomass were about 0.2 mg/mL-1 carbohydrates, 0.085 mg/mL-1 proteins, and 0.16 mg/mL-1 oil of this dry weight. The C/N ratios of 1:1 or 10:1 induced up to 30% of the Chlorococcum humicola dry mass as oils. Growth and dry matter content were hindered at 50:1 C/N and oil content was reduced as a result. The fatty acid profile was strongly altered by the applied C.N ratios. The defatted leftovers of the grown alga, after oil extraction, were fermented by a newly isolated heterotrophic bacterium, identified as Bacillus coagulans OQ053202, to evolve hydrogen content as gas. The highest cumulative hydrogen production and reducing sugar (70 ml H2/g biomass and 0.128 mg/ml; respectively) were found at the C/N ratio of 10:1 with the highest hydrogen evolution efficiency (HEE) of 22.8 ml H2/ mg reducing sugar. The optimum treatment applied to the Chlorococcum humicola is C:N ratio of 1:1 for the highest dry mass, up to 30% dry mass as oils. Some fatty acids were induced while others disappeared, depending on the C/N ratios. The highest cumulative hydrogen production and reducing sugar were found at the C/N ratio of 10:1.

Asunto(s)

RESUMEN

Biohydrogen (H2) is an efficient form of renewable energy generated from various biological organisms. Specifically, primitive plants such as algae which are photosynthetic organisms can produce several commercial products, including biofuels due to their simple form, short life span, efficient photosynthetic capacity, and ability to grow in non-potable water sources. But these algae are often neglected and considered waste. Several studies have revealed the importance and role of algal species in generating biofuels, especially biohydrogen. Considerable research has been conducted in order to understand hydrogen production from algal sources. This review emphasizes the photolysis of water-based hydrogen production in algae apart from the metabolites fermentation process. The influence of physico-chemical factors, including oxygen scavengers, nanoparticles, and hydrogenases, was highlighted in this review to enhance H2 production from algal species. Also, several algal species used for hydrogen production are summarized in detail. Overall, this review intends to summarize the developments in hydrogen production from algal species keeping in view of excellent prospects. This knowledge certainly would provide a good opportunity for the industrial production of hydrogen using algal species, which is one of the most concerned areas in the energy sector.

RESUMEN

The current need for the upgradation of biohydrogen generation and contaminant removal in two-chambered microbial electrolysis cells (MECs) compels the design of alternatives i.e. bioelectrochemical systems (BESs) to conventional reactors. In this study, a novel three-chambered design of MEC (BES-1) was developed with a common anodic chamber and a two-cathodic chambers at both ends of the anodic chamber, separated by a membrane (MEC-MEC). To facilitate electricity recovery, a microbial fuel cell (MFC) was integrated with an MEC in BES-2. Cathodic hydrogen recovery of 8.89 and 4.81 mL/L.day, and organic matter removal of 82% and 76% were obtained in BES-1 and BES-2, respectively, demonstrating their capabilities for bioremediation. Electrochemical analyses also revealed that cathodic reduction reactions improved with the effective utilization of protons during integration. Our design regulates H2/O2-associated electrochemical reactions and is beneficial for maintaining pH equilibrium. From cost and energy perspectives, the integrated BES provides a platform for two different reactions simultaneously and is capable of boosting overall hydrogen recovery and organic matter removal. Moreover, the compactness and competitiveness of such an integrated BES increase its scope for real-world applications.

Asunto(s)

RESUMEN

Biohythane, a balanced mixture comprising bioH2 (biohydrogen) and bioCH4 (biomethane) produced through anaerobic digestion, is gaining recognition as a promising energy source for the future. This article provides a comprehensive overview of biohythane production, covering production mechanisms, microbial diversity, and process parameters. It also explores different feedstock options, bioreactor designs, and scalability challenges, along with techno-economic and environmental assessments. Additionally, the article discusses the integration of biohythane into waste management systems and examines future prospects for enhancing production efficiency and applicability. This review serves as a valuable resource for researchers, engineers, and policymakers interested in advancing biohythane production as a sustainable and renewable energy solution.

Asunto(s)

RESUMEN

Extremophilic microorganisms play a key role in understanding how life on Earth originated and evolved over centuries. Their ability to thrive in harsh environments relies on a plethora of mechanisms developed to survive at extreme temperatures, pressures, salinity, and pH values. From a biotechnological point of view, thermophiles are considered a robust tool for synthetic biology as well as a reliable starting material for the development of sustainable bioprocesses. This review discusses the current progress in the biomanufacturing of high-added bioproducts from thermophilic microorganisms and their industrial applications.

Asunto(s)

RESUMEN

Hydrogen (H2), a clean and versatile energy carrier, has recently gained significant attention as a potential solution for reducing carbon emissions and promoting sustainable energy systems. The yield and efficiency of the biological H2 production process primarily depend on sterilization conditions. Various strategies, such as heat inactivation and membrane-based sterilization, have been used to achieve desirable yields via microbial fermentation. Almost every failed biotransformation process is linked to nonsterile conditions at any reaction stage. Therefore, the production of renewable biofuels as alternatives to fossil fuels is more attractive. Pure sugars have been widely documented as a costly feedstock for H2 production under sterile conditions. Biotransformation under nonsterile conditions is more desirable for stable and sustainable operation. Low-cost feeds, such as biowaste, are considered suitable alternatives, but they require appropriate sterilization to overcome the limitations of inherited or contaminating microbes during H2 production. This article describes the status of microbial fermentative processes for H2 production under nonsterile conditions and discusses strategies to improve such processes for sustainable, cleaner production.

RESUMEN

Furfural-tolerant and hydrogen-producing microbial consortia were enriched from soil, with hydrogen production of 259.84 mL/g-xylose under 1 g/L furfural stress. The consortia could degrade 2.5 g/L furfural within 24 h in the xylose system, more efficient than in the sugar-free system. Despite degradation of furfural to furfuryl alcohol, the release of reactive oxygen species and lactate dehydrogenase was also detected, suggesting that furfuryl alcohol is also a potential inhibitor of hydrogen production. The butyrate/acetate ratio was observed to decrease with increasing furfural concentration, leading to decreased hydrogen production. Furthermore, microbial community analysis suggested that dominated Clostridium butyricum was responsible for furfural degradation, while Clostridium beijerinckii reduction led to hydrogen production decrease. Overall, the enriched consortia in this study could efficiently degrade furfural and produce hydrogen, providing new insights into hydrogen-producing microbial consortia with furfural tolerance.

Asunto(s)

RESUMEN

Antibiotic fermentation residue, which is generated from the microbial antibiotic production process, has been a troublesome waste faced by the pharmaceutical industry. Dark fermentation is a potential technology to treat antibiotic fermentation residue in terms of renewable H2 generation and waste management. However, the inherent antibiotic in antibiotic fermentation residue may inhibit its dark fermentation performance, and current understanding on this topic is limited. This investigation examined the impact of the inherent antibiotic on the dark H2 fermentation of Cephalosporin C (CEPC) fermentation residue, and explored the mechanisms from the perspectives of bacterial communities and functional genes. It was found that CEP-C in the antibiotic fermentation residue significantly inhibited the H2 production, with the H2 yield decreasing from 17.2 mL/g-VSadded to 12.5 and 9.6 mL/g-VSadded at CEP-C concentrations of 100 and 200 mg/L, respectively. CEP-C also prolonged the H2-producing lag period. Microbiological analysis indicated that CEP-C remarkably decreased the abundances of high-yielding H2-producing bacteria, as well as downregulated the genes involved in hydrogen generation from the"pyruvate pathway" and"NADH pathway", essentially leading to the decline of H2 productivity. The present work gains insights into how cephalosporin antibiotics influence the dark H2 fermentation, and provide guidance for mitigating the inhibitory effects.

Asunto(s)

RESUMEN

Symbiosis between Glycine max and Bradyrhizobium diazoefficiens were used as a model system to investigate whether biohydrogen utilization promotes the transformation of the tetrachlorobiphenyl PCB77. Both a H2 uptake-positive (Hup+) strain (wild type) and a Hup- strain (a hupL deletion mutant) were inoculated into soybean nodules. Compared with Hup- nodules, Hup+ nodules increased dechlorination significantly by 61.1 % and reduced the accumulation of PCB77 in nodules by 37.7 % (p < 0.05). After exposure to nickel, an enhancer of uptake hydrogenase, dechlorination increased significantly by 2.2-fold, and the accumulation of PCB77 in nodules decreased by 54.4 % (p < 0.05). Furthermore, the tetrachlorobiphenyl transformation in the soybean root nodules was mainly testified to be mediated by nitrate reductase (encoded by the gene NR) for tetrachlorobiphenyl dechlorination and biphenyl-2,3-diol 1,2-dioxygenase (bphC) for biphenyl degradation. This study demonstrates for the first time that biohydrogen utilization has a beneficial effect on tetrachlorobiphenyl biotransformation in a legume-rhizobium symbiosis.

Asunto(s)

RESUMEN

Purple non-sulfur bacteria (PNSB) are a diverse group of bacteria studied for various possible applications. They are commonly surveyed in bioenergy research as they produce biohydrogen, a candidate for clean alternative energy. This study aimed to assess the biohydrogen production ability and genetically characterize a high biohydrogen-producing PNSB (MAY2) isolated from Los Baños, Laguna, Philippines via whole genome sequencing (WGS). MAY2, when grown in mixed volatile fatty acids, produced biogas with 38% hydrogen. WGS results revealed that the isolate is positively classified under the genus Rhodobacter johrii. Also, 82 genetic hallmarks for biohydrogen production were found in the isolated genome which are involved in the production of key enzymes and proteins relevant to the photofermentative and hydrogen regulation pathways. Its nitrogenase gene cluster is stringently regulated by two genes, nifA and rofN, whose function and expression are easily affected by several environmental factors.

Asunto(s)

RESUMEN

Colombia's continuous contamination of water resources and the low alternatives to produce biofuels have affected the fulfillment of the objectives of sustainable development, deteriorating the environment and affecting the economic productivity of this country. Due to this reality, projects on environmental and economic sustainability, phytoremediation, and the production of biofuels such as ethanol and hydrogen were combined. The objective of this article was to design and develop a sustainable system for wastewater treatment and the generation of biofuels based on the biomass of the aquatic plant Eichhornia crassipes. A system that simulates an artificial wetland with live E. crassipes plants was designed and developed, removing organic matter contaminants; subsequently, and continuing the sustainability project, bioreactors were designed, adapted, and started up to produce bioethanol and biohydrogen with the hydrolyzed biomass used in the phytoremediation process, generating around 12 g/L of bioethanol and around 81 ml H2/g. The proposed research strategy suggests combining two sustainable methods, bioremediation and biofuel production, to preserve the natural beauty of water systems and their surroundings.

Asunto(s)

RESUMEN

The global climate change mainly caused by fossil fuels combustion promotes that zero-carbon hydrogen production through eco-friendly methods has attracted attention in recent years. This investigation explored the biohydrogen production by co-fermentation of corn straw (CS) and excess sludge (ES), as well as comprehensively analyzed the internal mechanism. The results showed that the optimal ratio of CS to ES was 9:1 (TS) with the biohydrogen yield of 101.8 mL/g VS, which was higher than that from the mono-fermentation of CS by 1.0-fold. The pattern of volatile fatty acids (VFAs) indicated that the acetate was the most preponderant by-product in all fermentation systems during the biohydrogen production process, and its yield was improved by adding appropriate dosage of ES. In addition, the content of soluble COD (SCOD) was reduced as increasing ES, while concentration of NH4+-N showed an opposite tendency. Microbial community analysis revealed that the microbial composition in different samples showed a significant divergence. Trichococcus was the most dominant bacterial genus in the optimal ratio of 9:1 (CS/ES) fermentation system and its abundance was as high as 41.8%. The functional genes prediction found that the dominant metabolic genes and hydrogen-producing related genes had not been significantly increased in co-fermentation system (CS/ES = 9:1) compared to that in the mono-fermentation of CS, implying that enhancement of biohydrogen production by adding ES mainly relied on balancing nutrients and adjusting microbial community in this study. Further redundancy analysis (RDA) confirmed that biohydrogen yield was closely correlated with the enrichment of Trichococcus.

Asunto(s)

RESUMEN

This study introduces a two-stage hydrogen production enhancement mechanism using natural particle additives, with a focus on the effects of thermally modified maifanite (TMM) and pH self-regulation on dark fermentation (DF). Initial single-factor experiments identified preliminary parameters for the addition of TMM, which were further optimized using a Box-Behnken design. The established optimal conditions which include mass of 5.5 g, particle size of 120 mesh, and temperature of 324 °C, resulted in a 28.7 % increase in cumulative hydrogen yield (CHY). During the primary hydrogen production stage, TMM significantly boosted the growth and activity of Clostridium_sensu_stricto_1, enhancing hydrogen output. Additionally, a pH self-regulating phenomenon was observed, capable of initiating secondary hydrogen production and further augmenting CHY. These findings presented a novel and efficient approach for optimizing biohydrogen production, offering significant implications for future research and application in sustainable energy technologies.

Asunto(s)

RESUMEN

The production of caproic acid (CA) and hydrogen gas (H2) from organic wastewater is economically attractive. The Ruminococcaceae bacterium CPB6 has demonstrated potential for CA production from lactate-containing wastewater. However, our understanding of the effects of Fe2+ and Mg2+ on the growth and metabolism of strain CPB6 remains limited. Therefore, this study aims to investigate the impact of Fe2+ and Mg2+ on CA and H2 production, as well as on the expression of key genes involved in CA and H2 biosynthesis pathway. The results indicate that Fe2+ positively affects cell proliferation and H2 production while minimally impacting CA production. The highest levels of H2 production were achieved with the addition of 200 mg/L Fe2+. Conversely, Mg2+ significantly enhances CA and H2 production, with the optimal yield observed in a medium enriched with 300 mg/L Mg2+. Reverse transcription quantitative PCR (RT-qPCR) analysis reveals that Fe2+ promotes the expression of the hydrogenase gene, whereas Mg2+ has a negligible effect on hydrogenase expression. Notably, Fe2+ and Mg2+ inhibit the expression of key genes involved in CA synthesis. These findings suggest that Fe2+ enhances H2 production by boosting cell biomass and the expression of the hydrogenase gene, whereas Mg2+ improves CA and H2 production primarily by increasing cell biomass rather than influencing the expression of functional genes involved in CA biosynthesis.

RESUMEN

Water scarcity is a significant global issue caused by the prolonged disregard and unsustainable management of this essential resource by both public and private bodies. The dependence on fossil fuels further exacerbates society's bleak environmental conditions. Therefore, it is crucial to explore alternative solutions to preserve our nation's water resources properly and promote the production of biofuels. Research into the utilization of E. crassipes to remove heavy metals and generate biofuels is extensive. The combination of these two lines of inquiry presents an excellent opportunity to achieve sustainable development goals. This study aims to develop a sustainable wastewater treatment system and generate biohydrogen from dry, pulverized E. crassipes biomass. A treatment system was implemented to treat 1 L of industrial waste. The interconnected compartment system was built by utilizing recycled PET bottles to generate biohydrogen by reusing the feedstock for the treatment process. The production of biological hydrogen through dark fermentation, using biomass containing heavy metals as a biohydrogen source, was studied. Cr (VI) and Pb (II) levels had a low impact on hydrogen production. The uncontaminated biomass of E. crassipes displayed a significantly higher hydrogen yield (81.7 mL H2/g glucose). The presence of Cr (IV) in E. crassipes leads to a decrease in biohydrogen yield by 14%, and the presence of Pb (II) in E. crassipes leads to a decrease in biohydrogen yield of 26%. This work proposes a strategy that utilizes green technologies to recover and utilize contaminated water. Additionally, it enables the production of bioenergy with high efficiency, indirectly reducing greenhouse gases. This strategy aligns with international programs for the development of a circular economy.

RESUMEN

Consolidated bioprocessing (CBP) of lignocellulosic biomass holds promise to realize economic production of second-generation biofuels/chemicals, and Clostridium thermocellum is a leading candidate for CBP due to it being one of the fastest degraders of crystalline cellulose and lignocellulosic biomass. However, CBP by C. thermocellum is approached with co-cultures, because C. thermocellum does not utilize hemicellulose. When compared with a single-species fermentation, the co-culture system introduces unnecessary process complexity that may compromise process robustness. In this study, we engineered C. thermocellum to co-utilize hemicellulose without the need for co-culture. By evolving our previously engineered xylose-utilizing strain in xylose, an evolved clonal isolate (KJC19-9) was obtained and showed improved specific growth rate on xylose by ∼3-fold and displayed comparable growth to a minimally engineered strain grown on the bacteria's naturally preferred substrate, cellobiose. To enable full xylan deconstruction to xylose, we recombinantly expressed three different ß-xylosidase enzymes originating from Thermoanaerobacterium saccharolyticum into KJC19-9 and demonstrated growth on xylan with one of the enzymes. This recombinant strain was capable of co-utilizing cellulose and xylan simultaneously, and we integrated the ß-xylosidase gene into the KJC19-9 genome, creating the KJCBXint strain. The strain, KJC19-9, consumed monomeric xylose but accumulated xylobiose when grown on pretreated corn stover, whereas the final KJCBXint strain showed significantly greater deconstruction of xylan and xylobiose. This is the first reported C. thermocellum strain capable of degrading and assimilating hemicellulose polysaccharide while retaining its cellulolytic capabilities, unlocking significant potential for CBP in advancing the bioeconomy.

Asunto(s)

RESUMEN

Complex organic matter represents a suitable substrate to produce hydrogen through dark fermentation (DF) process. To increase H2 yields, pretreatment technology is often required. The main objective of the present work was to investigate thermo-acid pretreatment impact on sugar solubilization and biotic parameters of DF of sorghum or organic fraction of municipal solid waste (OFMSW). Biochemical hydrogen potential tests were carried out without inoculum using raw or thermo-acid pretreated substrates. Results showed an improvement in sugar solubilization after thermo-acid pretreatments. Pretreatments led to similar DF performances (H2 and total metabolite production) compared to raw biomasses. Nevertheless, they were responsible for bacterial shifts from Enterobacteriales towards Clostridiales and Bacillales as well as metabolic changes from acetate towards butyrate or ethanol. The metabolic changes were attributed to the biomass pretreatment impact on indigenous bacteria as no change in the metabolic profile was observed after performing thermo-acid pretreatments on irradiated OFMSW (inactivated indigenous bacteria and inoculum addition). Consequently, acid pretreatments were inefficient to improve DF performances but led to metabolic and bacterial community changes due to their impact on indigenous bacteria.

Asunto(s)

RESUMEN

The global energy crisis has intensified the search for sustainable and clean alternatives, with biohydrogen emerging as a promising solution to address environmental challenges. Leveraging photo fermentation (PF) process, purple phototrophic bacteria (PPB) can harness reducing power derived from organic substrates to facilitate hydrogen production. However, existing studies report much lower H2 yields than theoretical value when using acetate as carbon source and ammonia as nitrogen source, primarily attributed to the widely employed pulse-feeding mode which suffers from ammonia inhibition effect on nitrogenase. To address this issue, a continuous feeding mode was applied to avoid ammonia accumulation in this study. On the other hand, other pathways like carbon fixation and polyhydroxyalkanoate (PHA) formation could compete reducing power with H2 production. However, the reducing power allocation under continuous feeding mode is not yet clear. In this study, the reducing power allocation and hydrogen production performance were evaluated under various ammonia loading, using acetate as carbon source and infrared LED at around 50 W·m-2 as light source. The results show that (a) The absence of ammonia resulted in the best performance for hydrogen production, with 44 % of the reducing power distributed to H2 and the highest H2 volumetric productivity, while the allocation of reducing power to hydrogen production stopped when ammonia loading was above 7.6 mg NH4-N·L-1·d-1; (b) when PPB required to eliminate reducing power under ammonia limited conditions, PHA production was the preferred pathway followed by the hydrogen production pathway, but once PHA accumulation reached saturation, hydrogen generation pathway dominated; (c) under ammonia limited conditions, the TCA cycle was more activated rendering higher NADH (i.e. reducing power) production compared with that under ammonia sufficient conditions which was verified by metagenomics analysis, and all the hydrogen production, PHA accumulation and carbon fixation pathways were highly active to dissipate reducing power. This work provides the insight of reducing power distribution and PPB biohydrogen production variated by ammonia loading under continuous feeding mode.

Asunto(s)

RESUMEN

Cyanobacteria are among the most suitable organisms for the capture of excessive amounts of CO2 and can be grown in extreme environments. In our research we use the single-celled freshwater cyanobacteria Synechococcus elongatus PCC7942 PAMCOD strain and Synechocystis sp. PCC6714 for the production of carbohydrates and hydrogen. PAMCOD strain and Synechocystis sp. PCC6714 synthesize sucrose when exposed to salinity stress, as their main compatible osmolyte. We examined the cell proliferation rate and the sucrose accumulation in those two different strains of cyanobacteria under salt (0.4 M NaCl) and heat stress (35 0C) conditions. The intracellular sucrose (mol sucrose content per Chl a) was found to increase by 50% and 108% in PAMCOD strain and Synechocystis sp. PCC6714 cells, respectively. As previously reported, PAMCOD strain has the ability to produce hydrogen through the process of dark anaerobic fermentation (Vayenos D, Romanos GE, Papageorgiou GC, Stamatakis K (2020) Photosynth Res 146, 235-245). In the present study, we demonstrate that Synechocystis sp. PCC6714 has also this ability. We further examined the optimal conditions during the dark fermentation of PAMCOD and Synechocystis sp. PCC6714 regarding H2 formation, increasing the PAMCOD H2 productivity from 2 nmol H2 h- 1 mol Chl a- 1 to 23 nmol H2 h- 1 mol Chl a- 1. Moreover, after the dark fermentation, the cells demonstrated proliferation in both double BG-11 and BG-11 medium enriched in NaNO3, thus showing the sustainability of the procedure.

Asunto(s)

RESUMEN

Hydrogen creates water during combustion. Therefore, it is expected to be the most promising environmentally friendly energy alternative in the coming years. This study used extract liquid obtained from the waste nigella sativa generated by the black cumin oil industry. The performance of biological hydrogen manufacturing via dark fermentation was investigated in the fluidized bed reactor (FBR) and completely stirred tank reactor (CSTR) under the operation conditions of pH 5.0, 4.0, and 6.0 and a hydraulic retention time (HRT) of 36 and 24 h. The performance of hydrogen manufacturing was determined to be good under an organic loading ratio (OLR) of 6.66 g.nigella sativa extract/L and pH 4.0. According to these conditions, the maximum amount of hydrogen in CSTR and FBR was found to be 20.8 and 7.6 mL H2/day, respectively. The operating process of the reactors displayed that a reduction in HRT augmented biohydrogen manufacturing. The work that used mixed culture found that the dominant microbial population at pH 4.0 involved Hydrogenimonas thermophila, Sulfurospirillum carboxydovorans, Sulfurospirillum cavolei, Sulfurospirillum alkalitolerans, and Thiofractor thiocaminus. No research on waste black cumin extract was found in biohydrogen studies, and it was determined that this substrate source is applicable for biological hydrogen manufacturing.