2005 Volume 6 Issue 1 Pages 45-52
Lactic acid fermentation from kitchen refuse by Rhizopus oryzae KPS 106 was studied in this work as a biological method of converting food waste into value added-products. Our aim was to achieve high-concentration and high-purity L (+) -lactic acid production. Several pretreatment methods to modify kitchen refuse as a medium were adopted: saccharification, natural precipitation, freezing and thawing technique, centrifugation and chromatography. The main component of sugar in saccharified kitchen refuse (SKR) was glucose (98.5% of total sugar) . The most efficient technique for removing suspended solids (SS) in SKR was a freezing and thawing technique, by which approximately 55% of SS was eliminated. Kitchen refuse syrup (KRS) as a separated sugar from SKR by ion-exclusion chromatography could be used as a substrate for lactic acid fermentation by R. oryzae KPS 106 in a submerged culture. Addition of some inorganic minerals to KRS was effective in enhancing sugar consumption and lactic acid production. The sugar in KRS medium was assimilated almost as well as glucose in synthetic medium. The lactic acid yield from the KRS and glucose media were 63.9±1.8% and 73.3±2.9% (w/w) (based on initial total sugar concentration), respectively after 72 h of rotary shaking at 35°C and a rate of 100 rpm. L (+) -lactic acid produced from KRS medium was 98.7±0.3% in purity. From these results, kitchen refuse was demonstrated to be a promising renewable substrate for lactic acid fermentation, a use that would be new strategy for converting food waste into value-added products.
