The influence of pH controlling using CaCO3 agains production of lactic acid from glucose by Rhizopus oryzae

Abstract

The aim of this research was to study lactic acid product from glucose by R. oryzae without pH controlling, with pH 5 controlling, pH 6 controlling, and pH 7 controlling. Control of pH was done to avoid the accumulation of organic acids that could make pH decreasing on fermentation medium. This research used a treatment medium without pH controlling and three treatment medium with pH controlling. A treatment medium without pH controlling was added by 0.1 g CaCO3 before fermentation while treatment medium with pH controlling were added by 5% CaCO3 until pH 5, 6, 7 for each medium after 24 hours fermentation. Control of pH were done every 12 hours during fermentation. Fermentation lasted for 72 hours. The parametric measurement included glucose analysis, biomass and lactic acid product were done at the age of fermentation 24, 36, 48, 60 and 72 hours. The results showed that glucose consumption, biomass and lactic acid product were increased following increasing fermentation age and happened at all of treatment medium. The highest lactic acid product was 35.75 g/L on medium with pH 6 controlling at 72 hours fermentation, with Yp/s was 0.31 and efficiency of lactic acid fermentation was 62%. Lactic acid product on medium without pH controlling, with pH 5 controlling and with pH 7 controlling were 30; 25.45; and 24.70 g/L.