Fermentative l-(+)-lactic acid production from defatted rice bran

Abstract

In this paper, attempts were made to use defatted rice bran as the only raw material in L-lactic acid fermentation. According to results in shaking flask experiments, the medium with yeast extract, glucose and salts could be completely replaced by defatted rice bran hydrolysates in Lactobacillus rhamnosus cultures. The defatted rice bran medium was then tested in a 5 L fermenter. A productivity of 3.63 g L⁻¹ h⁻¹ in batch fermentation was obtained, which was 1.64 times of that with corn steep powder, and it accounted for 97.06% of that with yeast extract. In the fed-batch fermentation combined with a temperature rise, the concentration, productivity, and yield were 210 g L⁻¹, 2.56 g L⁻¹ h⁻¹, and 93.74% respectively. Furthermore, the work proved the sufficient amount of B vitamins and salts in defatted rice bran hydrolysates, which can introduce an effective way to reduce the raw material cost and be beneficial for L-lactic acid production.