Bioconversion of Caulerpa racemosa derived galactose rich fraction to D-Tagatose using L-arabinose isomerase from Lactobacillus plantarum MTCC1407

A new source of galactose isolated from Caulerpa racemosa is used as raw material for D-tagatose conversion. D-galactose from Caulerpa derived galactose rich fraction (C-GF), which is 99.1% pure is employed in enzymatic bioconversion for D-tagatose using L-arabinose isomerase (l-AI) from Lactobacillus plantarum MTCC1407. The enzyme fraction with l-AI activity is purified to an apparent homogeneity evident on SDS-PAGE with a molecular mass of 59 kDa. Maximum l-AI activity of enzyme was observed at 50°C, pH 7.0 with 20 mM Mg2+ as cofactor. The potential of C-GF to act as D-tagatose feedstock was tested with varying concentrations of C-GF in 50 mM phosphate buffer added with obtained l-AI enzyme. This is compared with the results of pure D-galactose conversion using the same l-AI for better understanding of C-GF as tagatose raw material. Maximum equilibrium of 34.5% tagatose to C-GF galactose was obtained after 40 h producing 0.33 g tagatose/g galactose in C-GF.