Improvement in 5′-Position-selective Glucosylation of Pyridoxine by Verticillium dahliae TPU 4900

Abstract

  Optimization of culture and reaction conditions for 5′-position-selective transglucosylation to pyridoxine by Verticillium dahliae TPU 4900 was investigated. V. dahliae TPU 4900 had high transglucosylation activity when grown with soluble starch as a carbon source and organic nitrogens such as Esusan meat as a nitrogen source at 15–20°C. Both the yield of pyridoxine 5′-α-D-glucoside (PN-5′-α-G) and the 5′-position-selectivity reached a maximum when an intact-cell reaction was done at 50–60°C and pH 7 with additions of dextrin. The transglucosylation activity in culture broth was 71 times with the optimization of culture conditions that under the conditions used for screening. The productivity of PN-5′-α-G synthesis was 6.9 times that under the initial conditions when the reaction conditions of intact cells were optimized. From 1000 mM (206 g/L) pyridoxine hydrochloride, PN-5′-α-G was synthesized to the concentration of 300 mM (98.4 g/L as PN-5′-α-G) with 5′-selectivity of 85% in 53 h by intact cells of V. dahliae TPU 4900.