One-pot production of tagatose using L-arabinose isomerase from Thermotoga maritima and β-galactosidase from Aspergillus oryzae

The one -pot production of tagatose from lactose using recombinant L-arabinose isomerase (L -AI) from Thermotoga maritima and commercial beta-galactosidase (beta-gal) from Aspergillus oryzae was evaluated. The beta-gal and L -AI ratio (R (beta-gal/L-AI)), initial lactose concentration and temperature were chosen as study variables. Maximum values of tagatose yield (Y-Tag), specific tagatose productivity (pi(Tag)) and sugars ratio (R-Tag/(Gal)) obtained were 23 %, 0.202 +/- 0.03 mmol Tag/(g prot & sdot;h) and 1, respectively. The composition of the product on a dry basis was as follows (g/ g): 0.23 tagatose, 0.232 galactose, 0.454 glucose, 0.043 fructose, 0.029 lactose and 0.012 GOS. The one -pot production was superior compared with a sequential operation, where values of 16.5 %, 0.11 mmol Tag/(g prot & sdot;h) and 0.59 were obtained for Y-Tag, pi(Tag) and R-Tag/(Gal), respectively.