Thesis (BS Food Technology) -- University of the Philippines Mindanao, 2003

This study investigated the potential of producing L (+)- lactic acid from sago starch using the local lactic acid bacteria (LAB) isolates (no. 78, 79, and 80) in a single-step simultaneous liquefaction and fermentation process. Substrate concentration (20.2 and 30.0 g/L pure sago starch) and incubation temperature (300 and 370C) were the factors considered in determining the optimum conditions for maximum lactic acid yield and conversion efficiency of starch to lactic acid. Samples for lactic acid concentration, residual starch, and microbial growth were obtained at 8-hour intervals for 24 hours. The microbial growth was determined by viable plate count while the lactic acid produced was analyzed by a standard curve, using 0.1N NaOH titrated against pure lactic acid. The residual starch was analyzed by first hydrolyzing the starch into glucose using strong acids, and the resulting glucose concentration was quantified using the Phenol-sulfuric method. Significantly higher lactic acid yield was observed when 20.0 g/L of initial substrate was used than with 30.0g/L. Lactic acid yield was found to be significantly higher at 300C incubation than at 370C. However, there was no significant difference on the lactic acid yield of the three isolates. On the other hand, starch conversion efficiency was not significantly affected by the factors studied.