Liquefied Sorghum Starch Medium as Novel Substrate for Production of Lactic Acid by Immobilized Acid Resistant Rhizopus oryzae in Natural and Synthetic Sponges

Lactic acid production by acid resistance UV mutated Rhizopus oryzae UV-40 strain immobilized on Natural-Vegetable Loofa Sponge (NVLS) and Synthetic Sponge (SS) was evaluated. Shape and texture of these matrices remained invariable with pH and temperature. Four pieces of NVLS and/or SS inocula per 150 ml of liquefied sorghum medium inoculated with spore suspension of 3×10⁶ and 2×10⁶ spores/ml resulted in 2.69 and 2.56 g/l/h lactic acid up to 4^th and 3^rd cycles of repeated batch fermentations, respectively. Scanning electron microscopic studies revealed NVLS is better adsorbing and immobilizing agent than SS. The mycelia in case of NVLS, inocula was strongly bound and entangled in between the matrices of the loofa sponge while in case of SS, inoculum was found to be better than the free cell and NVLS as well as production of maximum lactic acid.