A study of dextran production from maltodextrin by cell suspensions of Gluconobacter oxydans NCIB 4943

This study investigated dextran synthesis from a commercial maltodextrin su bstrate using cell suspensions of G. oxydans NCIB 4943 as catalysts. Experi ments were arranged according to a central composite statistical design. Th e effects of substrate concentration (10-100 g l(-1)), cell concentration ( 0.32-32.0 g wet weight l(-1)), time of reaction (8-48 h) and pH (3.5-5.5), each at three levels, on dextran yield and dextran molecular weight (MW), w ere investigated. Response surface methodology was used to assess factor in teractions, and empirical models describing the two responses were fitted. Most of the variance in dextran yield could be explained by the fitted mode l (R-2 = 0.96). Dextran yield ranged from 1.21 to 41.69%. The presence of s ignificant negative quadratic effects of cell concentration and time indica ted that dextran yield reached a plateau and thus, optimum levels of cell c oncentration and time could be identified to maximize dextran yield. Dextra n MW ranged from 6.6 to 38 kDa and was characterized by the significant int eractions of reaction time with substrate concentration and cell concentrat ion. The model, however, could account for only 60% of the variance in dext ran MW. Possible reasons for this are discussed.