Cellulose Hydrolysis Mechanism And Microbial Diversity Change During Anaerobic Digestion Of Switchgrass For Methane

The study on microbial community structure of effective lignocellulose hydrolysis and methane production is a key question to settle down low efficiency of lignocelluloses utilization and biogas yield. In the paper, two experiments were used to discuss microbial diversity and lignocellulose hydrolysis mechanism of anaerobic digestion for methane from switchgrass. Switchgrass of mature and elongation stage was going to feed experiment, respectively and then collected rumen fluid. Analysis difference of lignocellulose hydrolysis and methane production between rumen fluid domesticated by high lignocellulosic switchgrass（HSRF） and rumen fluid domesticated by low lignocellulosic switchgrass（LSRF）, which compared to these index of biogas fluid（BF） fermentation, further analysis microbial diversity difference of three kinds of fermentation fluid by High Throughput Sequencing Technology. Thus, the objectives of this study were to disclose microbial community structure of effective lignocelluloses hydrolysis and methane production.1. Compared study on rumen fluid and biogas fluid. HSRF, LSRF and BF were used for fermentation inoculums to digest swithgrass with lmm, fermented at37℃for72h. Biogas yield and composition, and VFA, NH3-N, WSC and pH were analyzed, and NDF and ADF of residue were determined. The result showed that total biogas yield and the highest methane content were as followed:LSRF（265ml）>HSRF（157ml）>BF（120ml） and BF（33.76%）>LSRF（27.36%）>HSRF（24.05%）, respectively. There was no significant difference in maximum dry matter digestion for two kinds of domesticated rumen fluid biogas fluid, as followed LSRF（29.00%）>HSRF（28.71%）>BF（21.39%）, but rumen fluid was significant difference compared to BF（P<0.05）. In addition, while hemicellulose hydrolysis was higher than cellulose hydrolysis in three of digestion system, there was no significant for LSRF and HSRF （P>0.05）, while rumen fluid was higher than BF （P<0.05）. the oder of cellulose was as followed:LSRF（36.89%）>HSRF（32.32%）>BF（13.47%）. The oder of VFA was all as followed:AA> PA>BA, and AA concentration of rumen fluid was significant difference compared to biogas fluid （P <0.05）, which indicated that AA was hardly utilized in rumen fluid, resulted in acidification and digestion process inhibed with pH of5.5and NH3-N of2.3g/1, and AA and PA was well utilized in biogas fluid with pH of6.5and NH3-N of1.8g/1. Enzyme activity of three of fermention fluid was as followed:BF>LSRF>HSRF.2. Compared study on microbial diversity of rumen and biogas fluid. HSRF, LSRF and BF sample collected were sequenced by high-throughput-sequencing, which of bacteria, fungus and archeae diversity were studied. The result showed that Bacteria distribution was mainly Ruminococcaceae, Rikenellaceae, Prevotellaceae, Lachnospiraceae, BSll_gut_group for rumen fluid, while was lie in Ruminococcaceae and Rikenellaceae in biogas fluid. Relativity of bacterial abundance between rumen fluid was very high, but there was very low relativity compared to biogas fluid. Abundance difference of fungus was lower than bacteria and archeae. Fungus distribution of HSRF, LSRF and BFwas all mainly in Neocallimastigaceae, which ratio were48.36%,78.06%and67.15%. There was high relativity between LSRF and HSRF, and lower relativity compared to BF. Rumen fluid included many Archaea_unclassified and Euryarchaeota_unclassified with90.96%and86.99%. Biogas fluid include Miscellaneous_Crenarchaeotic_Group_norank, Methanocorpusculaceae, Deep_Sea_Euryarchaeotic_Group, Methanosaetaceae and Deep_Sea_Hydrothermal_Vent_Gp₆, and these archaea family was no found in rumen fluid, which may be reason for low methane yield in of rumen fluid,In the whole, Bacterial, fungus and archeae abundance of domesticated rumen fluid was all higher biogas fluid. Bacterial quantity increasing of Ruminococcaceae, Rikenellaceae, Prevotellaceae and Lachnospiraceae could improve lignocelluloses hydrolysis. Microbial species and quantity increasing of Ruminococcaceae and Neocallimastigaceae play an important role in lignocellulosic hydrolysis. Miscellaneous_Crenarchaeotic_Group_norank, Methanocorpusculaceae and Methanosaetaceae could advance methane production. Rumen fluid domesticated by low lignocellulosic switchgrass was benefit to cellulose hydrolysis among three kinds of fermentation fluid, and microbial community of biogas fluid was favorable to ability of methane production.