BATCH AND CONTINUOUS PRODUCTION OF LACTIC ACID USING LACTOBACILLUS BULGARICUS (ATCC 8001)

Abstract

In this work lactic acid was produced in batch and continuous fermentation processes. The objective of this work was to investigate the effects of initial substrate concentration (30-120 g/l) and hydraulic retention time (HRT: 10-40 h) on cell growth, lactose utilization and lactic acid production. Whey lactose was used in batch and continuous systems; obtained results were compared. Substrate and product inhibitions were investigated at high initial substrate concentration. The results of continuous system indicate that production of lactic acid has increased with an increase in HRT along with increasing substrate concentration. The optimum initial lactose concentration for maximal lactic acid production in batch and continuous fermentation were found to be 90 and 120 g/l, respectively. The maximum concentrations of lactic acid in batch and continuous cultures were 32.1 and 42.9 g/l, respectively. The results showed that optimal lactic acid production was obtained at HRT of 30 hours. Mathematical projection model and kinetic studies for lactic acid production in batch cultures were performed. It was found that initial lactose concentration of 60g/l resulted in maximum specific growth rate of 0.215h-1