Bioconversion of C1 gases and genetic engineering modification of gas-utilizing microorganisms / 生物工程学报

C1 gases including CO, CO2 and CH4, are mainly derived from terrestrial biological activities, industrial waste gas and gasification syngas. Particularly, CO2 and CH4 are two of the most important greenhouse gases contributing to climate change. Bioconversion of C1 gases is not only a promising solution to addressing the problem of waste gases emission, but also a novel route to produce fuels or chemicals. In the past few years, C1-gas-utilizing microorganisms have drawn much attention and a variety of gene-editing technologies have been applied to improve their product yields or to expand product portfolios. This article reviewed the biological characteristics, aerobic or anaerobic metabolic pathways as well as the metabolic products of methanotrophs, autotrophic acetogens, and carboxydotrophic bacteria. In addition, gene-editing technologies (e.g. gene interruption technology using homologous recombination, group Ⅱ intron ClosTron technology, CRISPR/Cas gene editing and phage recombinase-mediated efficient integration of large DNA fragments) and their application in these C1-gas-utilizing microorganisms were also summarized.

Anaerobic co-digestion of Pennisetum hybrid and pig manure: A comparative study of performance and microbial community at different mixture ratio and organic loading rate.

To investigate how the changes in performance and the microbial community of the co-digestion system of Pennisetum hybrid and pig manure, two co-digestion systems in a semi-continuous mode were established at different grass:manure mixture ratios (50:50 and 75:25), and at variable organic loading rates (OLRs). The two reactors were in a steady-state at the OLRs of 2.0-5.0 g VS/(L·d), with the specific and volumetric biogas yields of 383.86 ± 65.13 to 574.28 ± 72.04 mL/g VS and 0.87 ± 0.07 to 2.36 ± 0.13 m3/(m3·d), respectively. The co-digestion system with a mixture ratio of 75:25 failed at an OLR of 5.5 g VS/(L⋅d). This failure could be attributed to the accumulation of volatile fatty acids (VFAs) owing to the imbalance between acid-production and -oxidation bacteria. By contrast, the co-digestion system with mixture ratio of 50:50 failed at an OLR of 7.0 g VS/(L⋅d), which was likely due to mechanical issues or improper reactor configuration. The genus Proteiniphilum contributed to the increase in total ammonia nitrogen. These findings provide useful guidance for optimizing co-digestion system, enhancing reactor performance and improving the wastes treatment.

Effect of bioaugmentation on the microbial community and mono-digestion performance of Pennisetum hybrid.

In this study, bioaugmentation with methanogenic propionate-utilizing enrichment was investigated as a method to improve the mono-digestion performance of Pennisetum hybrid in a semi-continuous mode. The effect of bioaugmentation on the microbial community was analyzed as well. The results demonstrate that the steady-state organic loading rate (OLR) of the bioaugmented reactor increased to 4.0 g VS/(L·d) with a volumetric biogas production of 1.95 ±â€¯0.17 m3/(m3·d). In contrast, the non-bioaugmented reactor failed at an OLR of 2.0 g VS/(L·d) accompanied with the accumulation of volatile fatty acids (VFAs). The results of whole genome pyrosequencing analysis suggest that the decrease in relative abundance of syntrophic butyrate and propionate oxidizers, such as Syntrophomonas, Syntrophobacter, and Syntrophorhabdus, reduced the conversion efficiency of butyrate and propionate which leads to the accumulation of butyrate and propionate, influencing the performance of the mono-digestion reactor. Conversely, in the bioaugmented reactor, the higher density of protein- and amino acid-utilizing bacteria, such as Proteiniphilum, Thermovirga, and Lutaonella, as well as the syntrophic association of Syntrophomonas spp. coupled with the methanogens Methanosarcina and Methanocella has a positive effect on system stability and performance.

Low-cost additive improved silage quality and anaerobic digestion performance of napiergrass.

Effects of molasses-alcoholic wastewater on the ensiling quality of napiergrass were investigated at ambient temperature, and its anaerobic digestion performance was assessed at mesophilic temperature. Results showed that the molasses-alcoholic wastewater had positive effect on silage quality and anaerobic digestion performance. Lower pH values of 5.20-5.28, lower NH3-N contents of 32.65-36.60 g/kg and higher lactic acid contents of 56-61 mg/kg FM were obtained for the silage samples with molasses-alcoholic wastewater addition. Higher specific biogas yield of 273 mL/g VS was obtained for the sample with 11% molasses-alcoholic wastewater added. Therefore 11% molasses-alcoholic wastewater addition was recommended.

Semi-dry mesophilic anaerobic digestion of water sorted organic fraction of municipal solid waste (WS-OFMSW).

An innovative municipal solid waste separation technology - water separation was developed in China recently. The purpose of this study was to evaluate the feasibility of anaerobic digestion from water sorted organic fraction of municipal solid waste (WS-OFMSW) to methane. A group of bench-scale (35 L) mesophilic (30 + or - 2 degrees Celsius) batch anaerobic digestions were carried out with three total solids in reactor (TSr = 16.0%, 13.5% and 11.0%). The biodegradability of WS-OFMSW with VS/TS of 61.6% was better than that of mechanically sorted OFMSW but still poor than that of source sorted OFMSW. No inhibitions of metal ions, volatile fatty acids and ammonia on anaerobic digestion were found. The reactors with TSr 16.0%, 13.5% and 11.0% achieved methane yield of 273, 283 and 314 L/kgVS and VS removal rate of 26.1%, 35.8% and 41.8%, respectively. The average methane content in biogas was about 66% for all reactors.

Progress in Research of Electrigens in Microbial Fuel Cell / 微生物学通报

Electricigens play an important role in microbial fuel cell(MFC) . This review provides an introduction of different electricigens on theirs taxonomical group,biochemical,physiological and morphological characteristics. The ability of electricity production of electricigens and electron transfer mechanisms in microbial fuel cells are also concluded. The prospect of waste water treatment and bio-electricity production is underlined,it is point out in this review that the future research of microorganism for MFC should be focused on enrichment,adaptation,modification and optimization by multi-strains application to improve the performances of MFC.