Abstract
Kitchen refuse showed a good potential as substrate for lactic acid fermentation by Rlzizopus oryzae in out previous study. For improved lactic acid production, immobilized cells of R. oryzae on loofa sponge (ICLS) were applied to exploit from kitchen refuse medium. Effects of size and conformation of loofa Sponge were investigated in comparison with other carriers. ICIS stability and fermentation efficiency were also evaluated. Loofa sponge showed better immobilization than other carriers. Lactic acid yield was significantly increased (p>0.05) with ICIS, 72.6±2.5% (w/w) was obtained while 63.7±3.8% (w/w) for free cells culture in shaking flask condition. The ICLS with 1.0×1.0×1.0 cm3 showed a great capability and successfully reused for few hatches. The average lactic acid yield in 3 repeatedd batches was 73.3±1.9% (w/w) . After 72 h, lactic acid yield from 1.0×1.0×1.0 cm3 of ICLS (based on the amount of sugar consumed) with 69.2% (w/w) and 70.5 g/L of final concentration were obtained when conducted in 1-L of bioreactor under agitation speed of 100 rpm, aeration rate of 1.0 vvm and at 35°C. These results demonstrate that lactic acid production from kitchen refuse medium by R. oryzae could be enhanced by immobilization on loofa sponge which is cheap and renewable material result in environment-friendly technology.
