Lactic acid production by loofah-immobilized Rhizopus oryzae through one-step fermentation process using starch substrate

Abstract

Rhizopus oryzae PTCC 5263 capacity in synthesis of lactic acid (LA) from 10 g/l of soluble potato starch was determined using one-step fermentation process. Pellets were the favorable growing form of the free cells. The extent of the natural ability of the test fungus on biofilm formation on loofah sponge was examined by immobilizing R. oryzae (LIRO). The maximum LA concentration for the free cells and LIRO within 96 h was 3 and 4 g/l, respectively. In terms of specific starch utilization rate ($q_{\text{s}}$) and specific LA formation ($q_{\text{p}}$), LIRO performed more favorably compared to the free cells ($q_{{{\text{s}}_{\text{F}} }} > q_{{{\text{s}}_{\text{LIRO}} }}$ and $q_{{{\text{p}}_{\text{F}} }} < q_{{{\text{p}}_{\text{LIRO}} }}$). Cell immobilization strategy was undertaken for the column reactor studies based on the statistically optimized levels of the inoculum size and temperature. Maximum production of the LA by the LIRO using an airlift reactor with net draft tube was 5 g/l obtainable within 48 h.