Butyric acid fermentation from rice straw with undefined mixed culture: Enrichment and selection of cellulolytic butyrate-producing microbial community

The study was conducted with an objective to present an alternative strategy for bioconversion of low grade lignocellulosic biomass into butyric acid without supplementary cellulolytic enzyme. Eight inocula sampled from various natural sources (cattle manure, pig manure compost, biogas residue, soil from the corn field, sediment from ditch, soil from shrub, rotten wood and rotten leaf) were used to start the enrichment procedure, which continued for over 8 months. The microbial community from the combination of cattle manure, pig manure compost, soil from corn field and rotten wood was selected for its stable cellulose-degrading potentials and high selectivity of butyric acid production from NaOH pretreated rice straw. The PCR-DGGE and sequence analysis revealed that the microbial community included cellulolytic and xylanolytic bacteria, butyrate-producing bacteria and other acidogenic bacteria.