Butyric Acid Fermentation from Rice Straw with Undefined Mixed Culture: Enhancement by pH Control

Abstract

This study aimed to find out the optimum pH range and a buffer feeding method for butyric acid production from rice straw by undefined mixed culture. A serial experiment was conducted at various pH levels from 5.0 to 7.0. The results showed that neutral pH improved rice straw conversion and hence carboxylic acid production. The highest butyric acid production was achieved at pH range of 6.0 to 6.5. Another serial experiment was performed at pH 6.0 to 6.5 buffered with CaCO3, NaHCO3, NH4HCO3 and their combinations, respectively. The results indicated that different buffers had different effects on product spectrum, and that CaCO3 combined with NaHCO3 was an effective buffer for butyric acid production. This study presents an alternative way for butyric acid production from lignocellulosic biomass without supplementary cellulolytic enzyme.