Factors affecting alpha,-1,2 glucooligosaccharide synthesis by Leuconostocmesenteroides NRRL B-1299 dextransucrase

The optimization of alpha -1,2 glucooligosaccharide (GOS) synthesis from ma ltose and sucrose by Leuconostoc mesenteroides NRRL B-1299 dextransucrase w as achieved using experimental design and consecutive analysis of the key p arameters. An increase of the pH of the reaction from 5.4 to 6.7 and of the temperature from 25 to 40 degreesC significantly favored alpha -1,2 GOS sy nthesis, thanks to a significant decrease of the side reactions, i.e., dext ran and leucrose synthesis. These positive effects were not sufficient to c ompensate for the decrease of enzyme stability caused by the use of high pH and temperature. However, the critical parameters were the sucrose to malt ose concentration ratio (S/M) and the total sugar concentration (TSC). alph a -1,2 GOS synthesis was favored at high S/M ratios. But using these condit ions also led to an increase of side reactions which could be modulated by choosing the appropriate TSC. Finally, with S/M = 4 and TSC= 45% w/v, dextr an and leucrose productions were limited and the final alpha -1,2 GOS yield reached 56.7%, the total GOS yield being 88%. (C) 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 74: 498-504, 2001.