METAGENOMICS COMBINED WITH HIGH-THROUGHPUT SEQUENCING REVEALS THE METHANOGENIC POTENTIAL OF FRESH CORN STRAW UNDER THERMOPHILIC AND HIGH OLR

Dry corn straw(DCS) is usually used in anaerobic digestion(AD), but fresh corn straw(FCS) has been given less consideration. In this study, the thermophilic AD of single-substrate(FCS and DCS) and co-digestion(straw with cattle manure) were investigated. The results show that when FCS was used as the single-substrate for AD, the methane production was 144 m L·g-1·VS-1, which was 7.5% and 19.6% higher than that of single DCS and FCS with cattle manure, respectively. In addition, the structure of FCS was loose and coarse,which was easier to be degraded than DCS. At the hydrolysis and acidification stages, Clostridium＿sensu＿stricto＿1, Clostridium＿sensu＿stricto＿7 and Sporosarcina promoted the decomposition of organic matter, leading to volatile fatty acids(VFAs) accumulation. Methanosarcina(54.4%) activated multifunctional methanogenic pathways to avoid the VFAs inhibition, which was important at the CH4production stage. The main pathway was hydrogenotrophic methanogenesis, with genes encoding formylmethanofuran dehydrogenase(K00200-K00203) and tetrahydromethanopterin Smethyltransferase(K00577-K00584). Methanosarcina also activated acetotrophic and methylotrophic methanogenesis pathways, with genes encoding acetyl phosphate(K13788) and methyl-coenzyme M reductase(K04480, K14080 and K14081), respectively. In the co-digestion, the methanogenic potential of FCS was also confirmed. This provides a scientific basis for regulating AD of crop straw.