BACTERIAL AMYLASE PRODUCTION BY THE L-LACTIC ACID-PRODUCING STRAIN USING CASSAVA STARCH SUPPLEMENTED WITH RICE BRAN

Abstract

Amylase is a crucial starch-degrading enzyme, which is commercially available, prvides benefit to starchy industry to overcome viscosity problem that caused by using high starch concentration, and to supply sugar residues. This study aimed to investigate the production of amylase by the potential optical pure L-lactic acid-producing Lactococcus sp. SUT 513 for further development of the optical pure acid fermentation process from the cheap cassava starch. Rice bran, the main byproduct in the process of rice milling, was found to provide the maximum amylase production when supplemented with 4.0 g/L (w/v) to the medium containing cassava starch (20.0 g/L, w/v), compared to the cassava medium added either the expensive nitrogen source, tryptone (5.0 g/L) and yeast extract (3.0 g/L, w/v); or the cheap alternatives, soy ptotein (8.0 g/L) or urea (2.0 g/L) combined with yeast extract (3.0 g/L). The amylase activity obtained from the developed medium was approximately 3 times higher than the original medium. This bacterium gave the highest crude amylase activity of 4.848±0.237 U/mL in the suitable medium performed in a7.5-L bioreactor with 3.0-L working volume for the optimal cultivation time of only 18 h under a control pH of 7.0, temperature at 35°C, agitation at 150 rpm, and without aeration. The results reveal the high potential production of amylase by Lactococcus sp. SUT 513 using the cheap cassava starch medium supplemented with rice bran, providing an opportunity to develop both amylase and optically pure L-lactic acid production processes.