Optimization and scale-up of l-lactic acid fermentation by mutant strain Rhizopus sp. MK-96-1196 in airlift bioreactors

Abstract

We determined the optimum culture conditions such as inoculum size, initial starch concentration, pH during the fermentation and aeration rate for l-lactic acid production by Rhizopus sp. MK-96-1196 in a 3- l airlift bioreactor. More than 90 g l of l-lactic acid was produced from only partially enzymatically hydrolyzed corn starch with a production rate of 2.6 g l / h and a product yield of 87% based on the starch consumed under the optimum conditions in the 3- l airlift bioreactor. Scale-up from the 3- l to a 100- l airlift bioreactor for l-lactic acid fermentation was carried out using V s (cm/s) as a scale-up criterion. The production rates and yields of l-lactic acid in both bioreactors appeared to be fairly well correlated with k L a (1/h).