Lactic acid production by loofa immobilized Rhizopus oryzae PTCC 5263: effect of the inoculum size

The Rhizopus oryzae PTCC 5263 as the lactic acid producer strain was examined in the present study and its ability in production of this organic acid was evaluated considering addition of spore suspension to the bare pieces of loofa sponge (loofa immobilized R. oryzae). Spore inoculum size is an important parameter in controlling the cell growth and morphology, where the highest level of spore suspensions added (3% v/v) to the growth medium containing ten pieces of loofa lignocellulosic fibre, put a limitation on efficiency of the cell growth and the mass transfer effects could adversely affect the cells performance, presence of loofa reduces the extent of the adverse conditions. The highest lactic acid production (50.95 g/l) was achieved with 2% (v/v) spore suspension. Final productivity and yield of lactic acid were 0.7 g/l/h and 45.13%, respectively. The maximum productivity (1.49 g/l/h) was obtained during first 72 hours of fermentation