Effect of Different Mixed Microflora on the Performance of Thermophilic Microaerobic Pretreatment

Abstract

h i g h l i g h t sThe effect of limited oxygen daily supplied on the AD of corn straw was studied. Daily oxygen supplied could obviously improve the AD performance of corn straw. Specific methanogenic activity under microaerobic condition improved slightly. The microbial community structure shift could explain the better AD performance. a r t i c l e i n f o b s t r a c tConventionally, oxygen is considered as inhibit factor of anaerobic digestion (AD). However, recent studies have demonstrated that AD performance could be enhanced by introducing limited amounts of oxygen (or air) directly into the anaerobic digester or during pretreatment step. In this study, impacts of microaeration on the anaerobic digestion of corn straw and the microbial community structure were investigated. Results showed that limited air introduced into fermentation system could improve the methane yield of corn straw. Maximum cumulative methane yield of 216.8 ml/g VS substrate and maximum VS removal efficiency of 54.3% were simultaneously obtained under microaerobic condition with the air load of 12.5 ml/L R per day, which were 16.5% and 10.3% higher than those of sample under anaerobic condition, respectively. Compared to anaerobic condition, the relative abundances of phylum Firmicutes, class Clostridia and order Clostridiales, which associated with hydrolysis process of AD were raised under microaerobic condition. In addition, the relative abundances of oxytolerant Methanosarcina and Methanobacterium were both doubled under microaerobic condition. Accordingly, specific methanogenic activity (SMA) under microaerobic condition improved slightly. The microbial community shift might be the reason for improved AD performance under microaerobic condition.

Anaerobic Co-digestion of Rice Straw and Pig Manure Pretreated With a Cellulolytic Microflora: Methane Yield Evaluation and Kinetics Analysis

“…Wang S. Q. et al ( 2018 ) used cellulase produced by Aspergillus niger to pretreat corn Stover at 50°C for 60 h, and the subsequent AD increased methane production by 36.9% compared with the unpretreated substrate. Fu et al ( 2016 ) used microaerobic bacteria to pretreat effluent from retted corn straw at 55°C and 130 rpm, which improved the methane yield by 21% and the VS removal rate by 10% during AD. This indicates that the pretreatment of lignocellulosic materials using cellulose-degrading microflora has a great application prospect.…”

Micro-aeration: an attractive strategy to facilitate anaerobic digestion

“…The analysis of the mechanisms of how methanogens survive under oxygen stress emphasizes that the inoculum used is crucial. An inoculum with a high abundance of 9 / 24 facultative anaerobes (e.g., microorganisms from the phylum Firmicutes) could help in rapid consumption of the oxygen molecules, thus protecting the methanogens from oxygen stress and secretion of additional extracellular hydrolases, thus benefiting substrate hydrolysis [63]. In addition to inoculum selection, the long-term domestication of the inoculum using micro-aeration could also cultivate a unique microbial community, which is able to function efficiently under micro-aeration conditions.…”