BIOCONVERSION OF WASTE OFFICE PAPER TO L(+)-LACTIC ACID BY FILAMENTOUS FUNGUS RHIZOPUS ORYZAE

抄録

L (+)-Lactic acid production was investigated using enzymatic hydrolysate of waste office (OA) paper as carbon source in culture of filamentous fungus Rhizopus oryzae. 82.8 g/L of glucose was consumed in 3 d culture, but only 7 g/L of xylose and 3.4 g/L of cellobiose contained in hydrolysate were consumed. From waste OA paper hydrolysate 49.1 g/L of lactic acid was produced with lactic acid yield of 0.53 (g lactic acid/g glucose consumed), which was no more than 67% to that from pure glucose medium. To find out the deviation of lactic acid productivity from glucose medium effects of ink-related compounds, pulp type, and additives added in paper manufacturing process were investigated. Hydrolysates from deinked waste OA paper and from filter paper, which did not contain ink-related compounds or additives, showed nearly the same lactic acid yield from the waste OA paper. However, hydrolysate from cellophane sheet that was made of dissolving pulp produced 77.9 g/L of lactic acid from 100 g/L of glucose, which was similar productivity to the glucose medium. Lactic acid yield from xylose that was derived from hemicellulose was 0.56 (g lactic acid/g consumed xylose), but that of cellobiose was 0.81 g/g. Among reducing sugars contained in hydrolysate xylose showed 40% lower lactic acid yield than that of glucose. It demonstrates that the cause of decrease in the lactic acid yield from waste OA paper hydrolysate is not the ink-related compounds and additives contained in hydrolysate, but unknown compounds derived from hemi-or lignocellulose.