EFFICIENT BIOTRANSFORMATION OF D-GALACTOSE TO D-TAGATOSE BY ACIDOTHERMUS CELLULOLYTICS ATCC 43068

An efficient method for biotransformation of D-galactose to D-tagatose was achieved by a whole-cell L-arabinose isomerase reaction of Acidothermus cellulolytics ATCC 43068 for the first time. It was observed that the strain grew well on the most carbon sources, whereas cells grown on cellobiose demonstrated the highest conversion capability. In addition, effect of reaction parameters such as pH, temperature and substrate concentration on the conversion of the isomerization was investigated. The optimum conversion ratio of D-galactose to D-tagatose reached 50.9% at pH 7.5, 75C when the substrate concentration was 50 mM. D-tagatose was separated to the purity of 95% by Ca(2+) cation exchange resin with a recovery of 83% and the identity of D-tagatose was confirmed by high-performance liquid chromatography analysis and (13)C-Nuclear Magnetic Resonance spectra. Acidothermus cellulolytics ATCC 43068 will be a good candidate of L-AI origin for D-tagatose production on a mass scale.