The enzymatic production of xylitol from xylose using xylose reductase of C. pelliculosa

coupling with the oxidoreductase system of Methanobacterium sp. capable of recycling NADP (H) has been demonstrated by Kitpreechavanich et al. (59). A sulfonated polysulfone membrane reactor for in situ regeneration and retention of coenzymes NADP (H) using the xylose reductase of C. pelliculosa coupled with oxidoreductase system of Methanobacterium sp. in the reduction of xylose to xylitol with hydrogen gas was also used (60). The membrane rejected the permeation of NADP (H) (92 and 97%) F420 (97%) and the required enzymes (100%) almost completely, but did not reject for the permeation of xylitol. Nishio et al. (67) reported the enzymatic conversion of xylose into xylitol by the immobilized cells of C. pelliculosa (NADP+ dependent xylose reductase) coupled with the immobilized cells of Methanobacterium sp. HU (hydrogenase and F420-NADP+ oxidoreductase) using hydrogen as an electron donor. The continuous production of xylitol in a column reactor packed with the co­immobilized cells could operate stably for 2 weeks. Xylitol was produced from xylose using commercial immobilized xylose isomerase from Bacillus coagulans and immobilized cells ofM smegmatis (30). From 10 g xylose, 4 g of xylitol was produced and 5 g xylose remained in the reaction mixture; no xylulose was detected. The washed cells of M smegmatis converted xylulose to xylitol under aerobic and anaerobic conditions. The washed cells of a gluconate-utilizing Corynebacterium strain grown in a gluconate-xylose medium produced xylitol from xylose in the presence of gluconate (29). Xylose was reduced to xylitol by coupling the xylose reductase activity to the 6- phosphogluconate dehydrogenase activity with NADP as a cofactor using cell-free extract and the fractionated enzymes of Corynebacterium strain.