Isomaltulose production by free cells of Serratia plymuthica in a batch process

Free cells of Serratia plymuthica were used to convert sucrose into isomaltulose and trehalulose reducing sugars. The effects of substrate concentration and temperature were observed in a batch process with flasks shaken at 150 rpm. The experimental design and response surface methodology analysis indicated that the conversion parameters had significant influence (p < 0.05) on sucrose conversion, and that a valid model was obtained after an analysis of variance (Fmodel = 10.48 > Fcharted = 5.79) to obtain a response surface and isocurve. Conversion was favoured when a 30% sucrose solution and temperature of 25 °C were used, which resulted in a high conversion into isomaltulose – over 70% – and 7–8% trehalulose. Small amounts of glucose (5–7%) and fructose (5–8%) were formed in the reaction medium.