Improvement of Biogas Production by Bioaugmentation

Biogas production technologies commonly involve the use of natural anaerobic consortia of microbes. The objective of this study was to elucidate the importance of hydrogen in this complex microbial food chain. Novel laboratory biogas reactor prototypes were designed and constructed. The fates of pure hydrogen-producing cultures of Caldicellulosiruptor saccharolyticus and Enterobacter cloacae were followed in time in thermophilic and mesophilic natural biogas-producing communities, respectively. Molecular biological techniques were applied to study the altered ecosystems. A systematic study in 5-litre CSTR digesters revealed that a key fermentation parameter in the maintenance of an altered population balance is the loading rate of total organic solids. Intensification of the biogas production was observed and the results corroborate that the enhanced biogas productivity is associated with the increased abundance of the hydrogen producers. Fermentation parameters did not indicate signs of failure in the biogas production process. Rational construction of more efficient and sustainable biogas-producing microbial consortia is proposed

Enhancing biogas production from agroindustrial waste pre-treated with filamentous fungi

Biogas is the product of anaerobic digestion (AD) of organic waste and is considered to be one of the most valuable natural renewable energy carriers. Plant biomass represents the most abundant eco-friendly energy reservoir on Earth. However, the tenacious and heterogeneous structure of the lignocellulose-rich elements makes it difficult for the involved microbes to digest the recalcitrant substrates. Both the degradation process and the biogas production yield can be enhanced by appropriate pre-treatment of lignocellulosic materials. Filamentous fungi have been known as proficient colonizers of lignocellulosic plant tissues and have been recognized as producers of exceptionally rich and diverse hydrolytic enzymes. We tested Aspergillus nidulans, Trichoderma reesei, Rhizomucor miehei and Gilbertella persicaria filamentous fungal strains for pre-treatment of various agricultural lignocellulosic wastes. During the pre-treatment phase, the beta-glucosidase and endoglucanase activity was measured spectrophotometrically. In the AD step, methane production was monitored by gas chromatography. The preliminary results showed that all the applied strains (Aspergillus nidulans, Trichoderma reesei, Rhizomucor miehei and Gilbertella persicaria) were highly effective in producing both beta-glucosidase and endo-(1,4)-beta-D-glucanase enzymes, which might explain the greatly improved AD results. Pre-treatment with the above-mentioned filamentous fungi positively affected the biogas production, although the effect strongly depended on the selection of the fungal partner for any given biomass substrate. Depending on the used substrate and the pre-treatment strain, overall methane yields were elevated two-fold relative to the controls

Biosurfactant Synthesis In the Oil Eater Rhodococcus Erythropolis MK1 Strain

Oil pollution is a very serious problem in the world. There were numerous oil spills in the last three decades and had great impact on the environment. They caused damages in wildlife as well as in economy by cutting down the agriculture, fishing, and tourism. Surfactants are useful weapons in the war against oil pollution. They are suitable to clean oil tanks and pipes and they are useful to solubilize animal fats in food industrial wastewater. Many bacteria can produce substantial amount of biosurfactants which can emulsify hydrophobic hydrocarbons, so that the native microflora can utilize the pollutants. An additional advantage of the biosurfactants over the synthetic surface active molecules is that these compounds are easily biodegradable. A special biosurfactant group is composed of mycolic acids which are basically α-alkyl, β-hydroxy fatty acids. Mycolic acids are the most characteristic components of the cell wall of the so called mycolata bacterial group. This group belongs to the Actinomycetales and contains the genera Mycobacterium, Corynebacterium, Nocardia, Rhodococcus and others. We aimed to map the mycolic acid biosynthesis pathway in Rhodococcus erythropolis MK1 strain isolated by us from polluted soil. In first step, we sequenced the genome of our strain by SOLIDTM next generation DNA sequencer. The reads were mapped on the R. erythropolis PR4 genome in the NCBI database. We searched for rhodococcal homologs of the known mycobacterial and corynebacterial genes involved in mycolic acid biosynthesis. We found conserved regions in the genome which are likely responsible for the biosynthesis of mycolic acids. The ongoing comparative whole genome transcript analysis will reveal the genes really necessary for the anabolism of mycolic acids

Bioaugmentation of biogas production by a hydrogen-producing bacterium

The rate-limiting nature of the hydrogen concentration prevailing in the anaerobic digester has been recognized, but the associated alterations in the microbial community are unknown. In response to the addition of Enterobacter cloacae cells in laboratory anaerobic digesters, the level of biogas production was augmented. Terminal restriction fragment length polymorphism (T-RFLP) and real-time polymerase chain reaction (Real-Time PCR) were used to study the survival of mesophilic hydrogen-producing bacteria and the effects of their presence on the composition of the other members of the bacterial community. E. cloacae proved to maintain a stable cell number and to influence the microbial composition of the system. Bioaugmentation by a single strain added to the natural biogas-producing microbial community was demonstrated. The community underwent pronounced changes as a result of the relatively slight initial shift in the microbiological system, responding sensitively to the alterations in local hydrogen concentration. © 2015 The Authors

Regulation of the methanogenesis pathways by hydrogen at transcriptomic level in time

The biomethane formation from 4 H-2 + CO2 by pure cultures of two methanogens, Methanocaldococcus fervens and Methanobacterium thermophilum, has been studied. The goal of the study was to understand the regulation of the enzymatic steps associated with biomethane biosynthesis by H-2, using metagenomic, pan-genomic, and transcriptomic approaches. Methanogenesis in the autotrophic methanogen M. fervens could be easily "switched off" and "switched on" by H-2/CO2 within about an hour. In contrast, the heterotrophic methanogen M. thermophilum was practically insensitive to the addition of the H-2/CO2 trigger although this methanogen also converted H-2/CO2 to CH4. From practical points of view, the regulatory function of H-2/CO2 suggests that in the power-to-gas (P2G) renewable excess electricity conversion and storage systems, the composition of the biomethane-generating methanogenic community is essential for sustainable operation. In addition to managing the specific hydrogenotrophic methanogenesis biochemistry, H-2/CO2 affected several, apparently unrelated, metabolic pathways. The redox-regulated overall biochemistry and symbiotic relationships in the methanogenic communities should be explored in order to make the P2G technology more efficient

Connection between the membrane electron transport system and Hyn hydrogenase in the purple sulfur bacterium, Thiocapsa roseopersicina BBS

Thiocapsa. roseopersicina BBS has four active [NiFe] hydrogenases, providing an excellent opportunity to examine their metabolic linkages to the cellular redox processes. Hyn is a periplasmic membrane-associated hydrogenase harboring two additional electron transfer subunits: Isp1 is a transmembrane protein, while Isp2 is located on the cytoplasmic side of the membrane. In this work, the connection of HynSL to various electron transport pathways is studied. During photoautotrophic growth, electrons, generated from the oxidation of thiosulfate and sulfur, are donated to the photosynthetic electron transport chain via cytochromes. Electrons formed from thiosulfate and sulfur oxidation might also be also used for Hyn-dependent hydrogen evolution which was shown to be light and proton motive force driven. Hyn-linked hydrogen uptake can be promoted by both sulfur and nitrate. The electron flow from/to HynSL requires the presence of Isp2 in both directions. Hydrogenase-linked sulfur reduction could be inhibited by a QB site competitive inhibitor, terbutryne, suggesting a redox coupling between the Hyn hydrogenase and the photosynthetic electron transport chain. Based on these findings, redox linkages of Hyn hydrogenase are modeled. © 2014 Elsevier B.V

Biodegradation of unctuous wastes of food industry

Nowadays, industrial emission of harmful materials is an extremely acute problem for humanity and Nature. Technologies with low or zero emission is of key importance to minimize the contamination of the ecosystem. However, vast amount of hazardous substances still gets out into the environment which must be made harmless. Bioremediation technologies using microorganisms to neutralize polluting materials are environmentally sound and economical tools for removal toxic compounds. It is a well-known fact that several Rhodococcus sp. can degrade a wide range of hazardous chemicals, such as aliphatic and aromatic hydrocarbons. In our laboratory, a Rhodococcus sp. was isolated from hydrocarbon polluted sites and it was successfully proven that the bacterium could efficiently degrade industrial hydrocarbons such as diesel oil and dead oil. The strain could tolerate low temperature and certain salt concentrations therefore it might be applied in oil mineralization after marine catastrophes. In this study, our aim was to test the ability of this strain to degrade food industrial and municipal waste. Lard, pig and poultry fat and cooking oil were used as sole carbon sources in minimal medium. The substrate utilization was demonstrated indirectly by measuring the respiration activity and CO2 production of the Rhodococcus sp. The strain could grow even at 10 g/1 of hydrocarbon concentration, it consumed the available oxygen and released remarkable amount of carbon dioxide within a week. These facts make this strain a promising waste cleaner both in food industrial applications and housekeeping

Inter-kingdom interactions and stability of methanogens revealed by machine-learning guided multi-omics analysis of industrial-scale biogas plants

Multi-omics analysis is a powerful tool for the detection and study of inter-kingdom interactions, such as those between bacterial and archaeal members of complex biogas-producing microbial communities. In the present study, the microbiomes of three industrial-scale biogas digesters, each fed with different substrates, were analysed using a machine-learning guided genome-centric metagenomics framework complemented with metatranscriptome data. This data permitted us to elucidate the relationship between abundant core methanogenic communities and their syntrophic bacterial partners. In total, we detected 297 high-quality, non-redundant metagenome-assembled genomes (nrMAGs). Moreover, the assembled 16 S rRNA gene profiles of these nrMAGs showed that the phylum Firmicutes possessed the highest copy number, while the representatives of the archaeal domain had the lowest. Further investigation of the three anaerobic microbial communities showed characteristic alterations over time but remained specific to each industrial-scale biogas plant. The relative abundance of various microorganisms as revealed by metagenome data was independent from corresponding metatranscriptome activity data. Archaea showed considerably higher activity than was expected from their abundance. We detected 51 nrMAGs that were present in all three biogas plant microbiomes with different abundances. The core microbiome correlated with the main chemical fermentation parameters, and no individual parameter emerged as a predominant shaper of community composition. Various interspecies H 2 /electron transfer mechanisms were assigned to hydrogenotrophic methanogens in the biogas plants that ran on agricultural biomass and wastewater. Analysis of metatranscriptome data revealed that methanogenesis pathways were the most active of all main metabolic pathways

Bioelectrochemical Systems (BES) for Biomethane Production-Review

Bioelectrochemical systems (BESs) have great potential in renewable energy production technologies. BES can generate electricity via Microbial Fuel Cell (MFC) or use electric current to synthesize valuable commodities in Microbial Electrolysis Cells (MECs). Various reactor configurations and operational protocols are increasing rapidly, although industrial-scale operation still faces difficulties. This article reviews the recent BES related to literature, with special attention to electrosynthesis and the most promising reactor configurations. We also attempted to clarify the numerous definitions proposed for BESs. The main components of BES are highlighted. Although the comparison of the various fermentation systems is, we collected useful and generally applicable operational parameters to be used for comparative studies. A brief overview links the appropriate microbes to the optimal reactor design