A novel and simple approach to the good process performance of methane recovery from lignocellulosic biomass alone

Lutispora saccharofermentans sp. nov., a mesophilic, non-spore-forming bacterium isolated from a lab-scale methanogenic landfill bioreactor digesting anaerobic sludge, and emendation of the genus Lutispora to include species which are non-spore-forming and mesophilic

A novel anaerobic, mesophilic, non-spore-forming bacterium (strain m25^T) was isolated from methanogenic enrichment cultures obtained from a lab-scale methanogenic landfill bioreactor containing anaerobic digester sludge. Cells were Gram-stain-negative, catalase-positive, oxidase-negative, rod-shaped, and motile by means of a flagellum. The genomic DNA G+C content was 40.11 mol%. The optimal NaCl concentration, temperature and pH for growth were 2.5 g l^-1, 35 °C and at pH 7.0, respectively. Strain m25^T was able to grow in the absence of yeast extract on glycerol, pyruvate, arginine and cysteine. In the presence of 0.2 % yeast extract, strain m25^T grew on carbohydrates and was able to use glucose, cellobiose, fructose, raffinose and galactose. The novel strain could utilize glycerol, urea, pyruvate, peptone and tryptone. The major fatty acids were iso-C_{15  :  0}, C_{14  :  0}, C_{16  :  0} DMA (dimethyl acetal) and iso-C_15 : 0 DMA. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the new isolate was closely related to Lutispora thermophila EBR46^T (95.02 % 16S rRNA gene sequence similarity). Genome relatedness was determined using both average nucleotide identity and amino acid identity analyses, the results of which both strongly supported that strain m25^T belongs to the genus Lutispora. Based on its unique phylogenetic features, strain m25^T is considered to represent a novel species within the genus Lutispora. Moreover, based on its unique physiologic features, mainly the lack of spore formation, a proposal to amend the genus Lutispora is also provided to include the non-spore-forming and mesophilic species. Lutispora saccharofermentans sp. nov. is proposed. The type strain of the species is m25^T (=DSM 112749^T=ATCC TSD-268^T).

Co-Ensiling of Wheat Straw as an Alternative Pre-Treatment to Chemical, Hydrothermal and Mechanical Methods for Methane Production

Wheat straw without pre-treatment is only converted to methane to a low degree during anaerobic digestion for fuel production due to its low hydrolysis. Current pre-treatment technologies are challenged by high expenses to energy or chemical agents. We examined the low-tech co-ensiling pre-treatment as an alternative pre-treatment of wheat straw, and compared the results with hydrothermal, chemical and mechanical pre-treatment methods. The effects of co-ensiling duration and the mixing ratio between straw and sugar beet root on the methane yields, surface morphology and chemical composition were examined. It was found that co-ensiling could improve production of methane by 34.7%, while a combined hydrothermal and chemical pre-treatment could increase the production of methane by 25.4%. The study demonstrated that the effect of co-ensiling could overlap with hydrothermal and chemical pre-treatment by having similar effects to increase lignocellulosic hydrolysis and improve methane production.

Urea-pretreated corn stover: Physicochemical characteristics, delignification kinetics, and methane production

Solids loading is a key factor in aqueous or gaseous ammonia production from urea. Methane production from urea-pretreated corn stover, as well as the physicochemical characteristics and delignification kinetics of the corn stover, were investigated with four solids loading values (10%-70%) and five ratios of urea to corn stover (1:100-7:10) at 35 °C for 6 weeks. A 1:20 ratio of urea to corn stover was optimal for achieving high lignin removal with ≤50% solids loading, and 7:10 was optimal with 70% solids loading. Under the two optimal conditions, 85.56% and 82.35% of cellulose and 85.76% and 85.49% of hemicellulose were retained. The maximum lignin removal rates of 69.67% and 68.27% and methane production of 294.70 and 292.56 L/kg volatile solids (VS) were achieved, respectively. The delignification kinetics of the urea-pretreated corn stover conformed to three first-order reactions. Most of the lignin was degraded within the first 3 weeks.

The mechanisms of biogenic methane metabolism by synergistic biodegradation of coal and corn straw

The mechanisms associated with the biomethane metabolism through the synergistic biodegradation of both coal and corn straw were explored to improve the utilization rate of corn straw. This applies to the filling of the goaf with corn straw and the production of biomethane using indigenous bacteria in the mine water with coal. The results showed that new macromolecular substances (e.g., Tetracosane and Pentacosane) were produced on the third day. A lower coal rank leads to a lower biodegradation rate of low-molecular-weight substances (e.g., butyric acid and valeric acid). Under the addition of coal samples, the biodegradation rate of cellulose, hemicellulose and lignin in corn straw could reached up to 29.82%, 35.79% and 6.16%, respectively. The addition of corn straw promoted the complementary advantages of archaeal genera (such as Methanosarina and Methanospirillum) and decreased the adverse bacterial genera (such as Desulfovibrio and Pseudomonas) in the fermentation system of single coal.

Improved biogas production and biodegradation of oilseed rape straw by using kitchen waste and duck droppings as co-substrates in two-phase anaerobic digestion

Oilseed rape straw (ORS) is a kind of biorefractory waste widely existing in the rural area of China, which is highly suitable to mix with kitchen waste (KW) and duck droppings (DD) in two-phase anaerobic digestion (AD). This research introduced the importance of KW and DD addition to improve the biogas production and biodegradation of ORS. A set of comparative experiments were conducted on two-phase mono- and co-digestion with organic load of 60 g VS/L. The total methane yield (TMY) and the biodegradation of ORS of co-digestions were obviously improving, and the synergistic effect found in the two-phase co-digestions. The optimum mixing ratio of ORS, KW and DD was 50:40:10, and the corresponding TMY and VS degradation rate of ORS were 374.5 mL/g VS and 49.7%, respectively. Addition of KW and DD maintained the pH within the optimal range for the hydrolyzing-acidification, improved the phase separation and buffering capacity of AD system.