Augmentation characteristics and microbial community dynamics of low temperature resistant composite strains LTF-27.

Biogas production in the cold regions of China is hindered by low temperatures, which led to slow lignocellulose biotransformation. Cold-adapted lignocellulose degrading microbial complex community LTF-27 was used to investigate the influence of hydrolysis on biogas production. After 5 days of hydrolysis at 15 ± 1 °C, the hydrolysis conversion rate of the corn straw went up to 22.64%, and the concentration of acetic acid increased to 2596.56 mg/L. The methane production rates of total solids (TS) inoculated by LTF-27 reached 204.72 mL/g, which was higher than the biogas (161.34 mL/g), and the control group (CK) inoculated with cultural solution (121.19 mL/g), the methane production rate of volatile solids (VS) increased by 26.88% and 68.92%, respectively. Parabacteroides, Lysinibacillus, and Citrobacter were the main organisms that were responsible for hydrolysis. While numerous other bacteria genera in the gas-producing phase, Macellibacteroides were the most commonly occurring one. Methanosarcina and Methanobacteriaceae contributed 86.25% and 11.80% of the total Archaea abundance during this phase. This study proves the psychrotrophic LTF-27's applicability in hydrolysis and biomass gas production in low temperatures.

The effect of heat pre-treatment on the anaerobic digestion of high-solid pig manure under high organic loading level.

Since more and more large-scale farms appear in China and changes in fecal sewage source disposal, the production of high-concentration solid manure waste is also increasing, and its conversion and utilization are gaining attention. This study investigated the effect of heat pre-treatment (HPT) on the thermophilic anaerobic digestion (AD) of high-solid manure (HSM). Pig manure (PM) feed with a total solids of 13% was used for the HPT and subsequent anaerobic digestion (AD) test. The HPT was carried out at 60°C, 80°C, and 100°C, respectively, for 15 min after the heating reached the set temperature. The results show that HPT led to PM feed COD solubilization, observing a maximum increase of 24.57% after pretreated at 100°C, and the treated PM feed under this condition received the maximum methane production potential of 264.64 mL·g-1 VS in batch AD test, which was 28.76% higher than that of the untreated group. Another semi-continuous AD test explored the maximum volume biogas production rate (VBPR). It involves two organic loading rates (OLR) of 13.4 and 17.8 g VSadded·L-1·d-1. The continuous test exhibited that all the HPT groups could produce biogas normally when the OLR increased to the high level, while the digester fed with untreated PM showed failure. The maximum VBPR of 4.71 L L-1·d-1 was observed from PM feed after pre-treated at 100°C and running at the high OLR. This reveals that thermal treatment can weaken the impact of a larger volume of feed on the AD system. Energy balance analysis demonstrates that it is necessary to use a heat exchanger to reuse energy in the HPT process to reduce the amount of energy input. In this case, the energy input to energy output (E i /E o ) ranged from 0.34 to 0.55, which was much less than one, suggesting that biogas increment due to heat treatment can reasonably cover the energy consumption of the pre-treatment itself. Thus combining HPT and high-load anaerobic digestion of PM was suitable.

Degradation of rice straw at low temperature using a novel microbial consortium LTF-27 with efficient ability.

In this study, a novel psychrotrophic lignocelluloses degrading microbial consortium LTF-27 was successfully obtained from cold perennial forest soil by successive enrichment culture under facultative anaerobic static conditions. The microbial consortium showed efficient degradation of rice straw, which cellulose, hemicelluloses and lignin lost 71.7%, 65.6% and 12.5% of its weigh, respectively, in 20 days at 15 °C. The predominant liquid products were acetic acid and butyric acid during degrading lignocellulose in anaerobic digestion (AD) process inoculated with the LTF-27. The consortium mainly composed of Parabacteroides, Alcaligenes, Lysinibacillus, Sphingobacterium, and Clostridium, along with some unclassified uncultured bacteria, indicating powerful synergistic interaction in AD process. A multi-species lignocellulolytic enzyme system working cooperatingly on lignocelluolse degradation was revealed by proteomics analysis of cellulose bound fraction of the crude extracellular enzyme, which provides key theoretical base for further exploration and application of LTF-27.