International Science and Technology Cooperation Center for Urban Alternative Water Resources Development, Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Engineering Technology Research Center for Wastewater Treatment and Reuse, Shaanxi, Key Laboratory of Environmental Engineering, Shaanxi, Xi'an University of Architecture and Technology, No. 13 Yanta Road, Xi'an 710055, China.
International Science and Technology Cooperation Center for Urban Alternative Water Resources Development, Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Engineering Technology Research Center for Wastewater Treatment and Reuse, Shaanxi, Key Laboratory of Environmental Engineering, Shaanxi, Xi'an University of Architecture and Technology, No. 13 Yanta Road, Xi'an 710055, China.
Sci Total Environ. 2020 May 1;715:136529. doi: 10.1016/j.scitotenv.2020.136529. Epub 2020 Jan 8.
Rumen fermentation is known to be effective for lignocellulosic-wastes biodegradation to certain extent but it is still unclear if there exists a termination of the microorganisms' action to further degrade the bio-refractory fractions. In order to illuminate the related microbiological characteristics, experiments were conducted in a prolonged duration of rumen fermentation of mechanically ruptured wheat straw, with inoculation of cow rumen microorganisms in vitro. Although the organic wastes could not be biodegraded quickly, continuous conversion of the lignocellulosic contents to volatile fatty acids and biogas proceeded in the duration of more than three months, resulting in 96-97% cellulose and hemicellulose decomposition, and 42% lignin decomposition. X-ray diffraction and Fourier transform infrared spectroscopy further demonstrated the characteristics of lignocellulosic structure decomposition. Under the actions of cow rumen microorganisms, stable pH was maintained in the fermentation liquid, along with a steady NH-N, volatile fatty acids accumulation, and a large buffering ability. It was identified by enzyme analysis and Illumina MiSeq sequencing that the rich core lignocellulolytic enzymes secreted by the abundant and diverse rumen bacteria and fungi contributed to the persistent degradation of lignocellulosic wastes. Members of the Clostridiales order and Basidiomycota phylum were found to be the dominant lignocellulolytic bacteria and fungi, respectively. It could thus be inferred that the main lignocellulose degradation processes were a series of catalytic reactions under the actions of lignocellulolytic enzymes secreted from bacteria and fungi. The dominant hydrogenotrophic methanogens (Methanomassiliicoccus, Methanobrevibacter, Methanosphaera, and Methanoculleus) in the rumen could also assist CH production if the rumen fermentation was followed with anaerobic digestion.
瘤胃发酵在一定程度上被认为对木质纤维素废物的生物降解是有效的，但目前尚不清楚微生物的作用是否会终止，以进一步降解生物难降解的部分。为了阐明相关的微生物学特性，进行了一项实验，即体外接种牛瘤胃微生物，对机械破碎的小麦秸秆进行长时间瘤胃发酵。虽然有机废物不能快速生物降解，但木质纤维素含量连续转化为挥发性脂肪酸和沼气，持续了三个多月，导致纤维素和半纤维素分解 96-97%，木质素分解 42%。X 射线衍射和傅里叶变换红外光谱进一步证明了木质纤维素结构分解的特征。在牛瘤胃微生物的作用下，发酵液中保持稳定的 pH 值，同时 NH-N、挥发性脂肪酸不断积累，具有较大的缓冲能力。通过酶分析和 Illumina MiSeq 测序鉴定，丰富的核心木质纤维素降解酶是由丰富多样的瘤胃细菌和真菌分泌的，这有助于木质纤维素废物的持续降解。厚壁菌门和担子菌门的梭菌目和担子菌目分别被鉴定为主要的木质纤维素降解细菌和真菌。因此，可以推断出主要的木质纤维素降解过程是一系列在细菌和真菌分泌的木质纤维素酶作用下的催化反应。瘤胃中主要的产氢甲烷菌（甲烷甲烷球菌、甲烷短杆菌、甲烷球菌和甲烷球菌）如果在瘤胃发酵后进行厌氧消化，也可以协助 CH 生成。
