Optimization of medium composition for the production of glucosyltransferase by Aspergillus niger with response surface methodology

Aspergillus niger CCRC 31494 produced an extracellular glucosyltransferase (EC 2.4.1.24) with a high transglucosylating activity. For production of glucosyltransferase by A. niger, yeast extract was the best nitrogen source after cultivation for 7 days. Addition of minerals to the medium showed no significant increase in the production of glucosyltransferase. A significant decrease in the production of glucosyltransferase was obtained when the initial pH of the medium was adjusted at 3 or 4. The concentration of inoculated spores of 5.8 x 10(6) or 1 x 10(7) per ml medium caused the higher production of glucosyltransferase. The central composite experimental design (CCD) and response surface methodology (RSM) were employed to derive a statistical model for the effects of maltose and yeast extract on the production of glucosyltransferase by A. niger. An initial concentration of 4.5% maltose and 6.6% yeast extract have been found optimum to maximize the production of glucosyltransferase. In addition, the time course of glucosyltransferase production by A. niger in the optimized medium composition was also described. (C) 1997 Elsevier Science Inc.