Distillery Stillage as a New Substrate for Lactic Acid Production in Batch and Fed-batch Fermentation

Abstract

Lactic acid and biomass production on distillery stillage - a by-product of bioethanol industry - was studied in this paper. Batch and fed-batch fermentation strategies for lactic acid production on distillery stillage were performed by Lactobacillus rhamnosus ATCC 7469. The most appropriate initial sugar concentration in the stillage was determined and different fermentation strategies were studied under selected conditions The most efficient sugar conversion in batch fermentation was attained with the initial sugar concentration of 55 g/L. Enhancement in lactic acid productivity (up to 1.80 g/Lh) and a very high number of viable cells (10(8) CFU/mL) were achieved in fed-batch fermentation. The high lactic acid concentration attained in fed-batch fermentation opened a new possibility for stillage processing. In addition, extensive bacterial growth achieved during fermentation of the stillage could bring additional value to the process through utilization of the spent media for animal feed formulae enriched in lactic acid bacteria.