The strain was cultivated in 500-ml Erlenmeyer flasks with 200 ml of ME
medium containing 1% sodium l-glutamate, at 55 ◦C and pH 8.5 with shaking
(200 rpm) for 36 h. Cells were harvested by centrifugation at 14,000×g for 5 min
and washed twice with distilled water before resuspending in 50mM Tris–HCl
buffer (pH 9.0). The reaction was carried out with 2% xylitol as substrate in
a 30ml L-shape tube with shaking (150 rpm) at 50 ◦C. Samples were taken at
regular intervals to determine ketose production.