Novel Butyric Acid Fermentation Strains and Their Performance in Fermenting Rice Straw by Pure and Mixed Culturing

Abstract

Abstract. Synergistic metabolism among mixed culture can be utilized to hydrolise and ferment cellulose and hemicellulose in rice straw to avoid high cost of saccharification and its complex procedure. Three buryric acid producing strains cellulose-decomposing bacteria named Clostridium cadaveris C4, cellubiose fermenting bacteria named C. butyricum B20, xylan-degrading bacteria named C. butyricum X3 respectively were isolated from undefined mixed culture which was enriched and cultured from rice straw. The fermentation experiment of rice straw was carried out to increase the burytic acid conversion rate with three single strain and their mixed strains. Fermentation results showed that co-fermentation with two or three strains can significantly improve the degradation of rice straw and yield of butyric acid because of synergistic effect in or among different metabolic strains. Among the experiment, co-culture of three strains with inoculum of 1.1 g-DCW/L got the butyric acid production rate 0.18 g/(g-DCW⋅h) during logarithmic period which increased by 50%, 200% and 63.64% compared with C4, B20 and X3 respectively.The results of the study provide the methodological guidance and bacterial strain resources for the butyric acid biotransformation from lignocellulosic biomass.