Production of L-Lactic acid from starch and food waste by amylolytic Rhizopus oryzae MTCC 8784

Lactic acid, commonly used in food, chemical and pharmaceutical industries, has recently received much attention for the production of biodegradable plastics. In this study, Rhizopus oryzae MTCC 8784 was used to convert starch into optically pure L-Lactic acid. Effect of time, pH, addition of calcium carbonate and starch concentration were analyzed using shaker flasks in order optimize the L-lactic acid concentration and volumetric productivity. Under optimized conditions [pH6.0, CaCO3 (10g/L), starch (10g/L) and 72 h of cultivation] R.oryzae MTCC 8784 gave a lactic acid concentration of 50.48g /L with a volumetric productivity (Qp) of 0.7 (g/L/h) and lactic acid yield(YP/s) of 4.54 g/g (2 fold increase), 100% starch saccharification, and 1.5 g/L mycelial biomass. To reduce the Lactic acid production costs, inexpensive raw materials such as food waste (fruit and vegetable peel/waste) like sapota, banana, papaya, potato, corn cob and carboxymethyl cellulose were explored. All substrates tested supported growth and lactic acid production. Efficient lactic acid concentration (72g/L) with a biomass of 1.9 g/L; volumetric productivity (Qp) of 1g/L/h and lactic acid yield(YP/s) of 3.6g/g was obtained with sapota peel fermentation. Lactic acid was detected in the fermentation broth by HPLC.