PRODUCTION OF L(+)-LACTIC ACID USING IMMOBILIZED RHIZOPUS-ORYZAE - REACTOR PERFORMANCE-BASED ON KINETIC-MODEL AND SIMULATION

The production of L(+)-lactic acid using alginate immobilized Rhizopus oryzae in tapered-column fluidized-bed batch reactor was tested and simulated using the kinetic data taken independently in shake-flask cultures. The data show saturation kinetics with substrate and product inhibitions in linear form. Analysis of the kinetic data gave kinetic constants: V-m, 11.04 g lactic acid/(L-bead. h); K-m, 20.9 g glucose/L; and K-i, 365 g glucose/L for lactic acid production. The product inhibition constant, K-p, was found to be 316 g lactic acid/L. The simulation results showed a good agreement with the experimental results when the initial lag phase was taken into account in the simulation model. Without the adjustment for the initial lag period, the kinetic model showed higher conversion. Starting with a glucose concentration of 150 g/L, it was possible to produce 73 g/L of L(+)-lactic acid in 44.5 h. The lactic acid yield was 64.8% by weight based on the amount of glucose consumed.