Galacto-oligosaccharide production using a recycling cell culture of Sterigmatomyces elviae CBS8119.

Addition of small amounts of Fe2+, Zn2+, Cu2+ and thiamine-HCL to the culture medium was required for promoting the galactooligosaccharide (Gal-OS)-producing activity of Sterigmatomyces elviae CBS8119, when the concentration of yeast extract in the medium was lowered to 0.1 g l-1. Galactooligosaccharide production using a recycling cell culture was performed in a medium containing 360 mg ml-1 of lactose supplemented with optimal concentrations of Fe2+ (1.5 mg l-1 of FeSO4 x 7H2O), Zn3+ (15 mg l-1 of ZnSO4 x 7H2O), Cu2+ (0.5 mg l-1 of CuSO4 x 5H2O) and thiamine-HCL (1 mg l-1). Galacto-oligosaccharide production was maintained at high levels during six cycles of production, with the amount of Gal-OS produced in each cycle being more than 216 mg ml-1 (weight yield of more than 60%.