Enhanced production of butyric acid by solid-state fermentation of rice polishings by a mutant strain of Clostridium tyrobutyricum

Abstract

Purpose: To enhance butyric acid production by solid-state fermentation with a hyper-producing mutant of Clostridium tyrobutyricum generated by random mutagenesis. Methods: Wild type C. tyrobutyricum was mutagenized with UV irradiation, nitrous acid, and ethidium bromide to obtain a hyper-producing strain. Various physiochemical parameters were optimized to increase the butyric acid yield. Results: The UV-induced mutant (C.TUV) produced significantly higher concentrations of butyric acid than the wild type parent, nitrous acid-induced, and ethidium bromide-induced strains. C.TUV increased butyric acid production 1.4-fold more than the parent strain. Fermentation with C.TUV with 2.5 g of rice polishings (w/w), a 2% inoculum volume (v/v), and a 48-h incubation period at 37°C under anaerobic conditions produced 11.63 mg/100 g of butyric acid. The addition of 0.6% corn steep liquor as a nitrogen source increased the butyric acid concentration to 26.09 mg/100 g. Conclusion: These optimized fermentation parameters on a small scale can be used on a commercial scale to mass-produce butyric acid.