Production of lactic acid with loofa sponge immobilized Rhizopus oryzae RBU2-10

Lactic acid production by Rhizopus oryzae RBU2-10 immobilized in loofa sponge was evaluated. Shape and texture of loofa sponge, which was obtained from the mature dried fruit of Luffa cylindrica, remained intact after its treatment with buffers of varying pH and following its repeated autoclaving for up to four cycles (121 °C, 20 min per cycle). The medium having four pieces of loofa sponge (1.008 cm3) per 100 ml medium and inoculated with 3 × 106 spores ml−1 resulted maximum production (80.75 g l−1) of lactic acid in 48 h of fermentation. Repeated batch fermentation for lactic acid production could be carried out for 10 cycles. Remarkably higher levels of productivity (1.66–1.84 g l−1 h−1) was obtained during first five cycles of fermentation with a maximum productivity (1.84 g l−1 h−1) obtained during third cycle of fermentation.