Kinetic behavior of Candida tropicalis during xylitol production using semi-synthetic and hydrolysate based media

摘要

The?effects of the xylose concentration and the air supply on the production of xylitol from D-xylose by the yeast?Candida tropicalis?(AY 2007) using semi-synthetic and hydrolysate based media were investigated in four fermentation batch runs.?The xylitol formation was favored under oxygen-limited conditions (2nd?experiment,?air flow rate 0.3 vvm)?with a maximum xylitol production (36.0gm/l) after 59h as compared with that obtained?in the 1st?experiment?(30.99?g/L) after 66 h?under relatively less oxygen limited condition (air flow rate 1.5 vvm).?Increasing the initial xylose concentration from 45.5 g/L?in the 2nd?experiment to 96.9 g/L in the 3rdexperiment led to a great decrease in the xylitol accumulation rate (Qp) from 0.506 to 0.134 g/L, xylitol yield coefficient (Yp/s) from 0.704 to 0.180 g/g?and a mild increase in the xylose consumption rate (Qs) from 0.70 to 0.75 g/L/h. The semi-synthetic medium (1st?and 2nd?experiments) had a maximum xylitol yield coefficient (Yp/s) of 0.701 and 0.704 g/g, respectively which?was?less than that obtained in the hydrolysate experiment (0.783 g/g). This is probably due to the low hydrolysate initial xylose content (29.8 g/L).