Lactulose production from lactose by recombinant cellobiose 2‐epimerase in permeabilised Escherichia coli cells

Summary C aldicellulosiruptor saccharolyticus cellobiose 2‐epimerase (Cs CE ) catalyses the single substrate lactose into lactulose and is the most efficient enzyme ever found for the enzymatic synthesis of lactulose. Ethanol‐permeabilised E scherichia coli cells containing Cs CE were used as biocatalysts for lactulose production. The reaction conditions for maximum lactulose production were optimised to be 600 g L −1 lactose, pH 7.5, 80 °C and 12.5 U mL −1 of whole‐cell biocatalyst. After incubated at Na 2 HPO 4 –NaH 2 PO 4 buffer for 2 h, approximately 390.59 g L −1 lactulose was obtained with a conversion yield of 65.1%. The lowest production and conversion yield of epilactose were also found in Na 2 HPO 4 –NaH 2 PO 4 buffer with a final concentration of 11.7 g L −1 and a conversion yield <2%. The results represent a promising technology to attain high production and conversion yield of lactulose with a high purity on industrial scale.