초록
The statistical experimental designs were adopted to optimize the culture medium in xylitol production by Candida tropicalis HDY-02 with corncob hemicellulose hydrolysate as substrate. In the first step, Plackett-Burman design was used for screening the important variables. KH<SUB>2</SUB>PO<SUB>4</SUB>, yeast extract, (NH<SUB>4</SUB>)<SUB>2</SUB>SO<SUB>4</SUB> and MgSO<SUB>4</SUB>.7H<SUB>2</SUB>O were found to significantly affect xylitol yield. In the second step, central composite design (CCD) was used to determine the optimum level of each of the significant variables. A second-order polynomial was determined by the multiple regression analysis of the experimental data. The interactive effects of yeast extract and MgSO<SUB>4</SUB>.7H<SUB>2</SUB>O on xylitol yield of C. tropicalis HDY-02 were determined to be significant. The validation experimental was consistent with the prediction model. The optimum combinations for xylitol yield were 5gl<SUP>-1</SUP> (NH<SUB>4</SUB>)<SUB>2</SUB>SO<SUB>4</SUB>, 1.3gl<SUP>-1</SUP> KH<SUB>2</SUB>PO<SUB>4</SUB>, 4.6gl<SUP>-1</SUP> yeast extract and 0.6gl<SUP>-1</SUP> MgSO<SUB>4</SUB>.7H<SUB>2</SUB>O. Under these optimal conditions, the continuous fed-batch experiments could produce xylitol of 58gl<SUP>-1</SUP> with a yield of 0.73gg<SUP>-1</SUP> xylose.