Two-stage seeding strategy and its multi-response optimization for enhanced xylitol production by Debaryomyces nepalensis NCYC 3413

The aim was to develop a two-stage seeding strategy and its optimization to enhance the conversion of xylose to xylitol by Debaryomyces nepalensis NCYC 3413. To develop efficient seed, multi-response optimization was employed to obtain optimal inoculum age and volume where xylitol concentration, yield and productivity were maximized. The optimal conditions of inoculation age and volume were 5.86 h and 11.66 % (v/v), respectively. Maximized results were observed at 48 h as compared to 72 h pre-optimization. Xylitol concentration slightly improved from 56 g/L to 59.71 g/L (p-value = 0.043). Yield improved from 0.56 g/g to 0.66 g/g (p-value = 0.044), whereas, productivity showed a significant increase from 0.76 g/L.h to 1.24 g/L.h (p-value = 0.008). Xylose Reductase activity improved by 1.67-folds and Xylitol Dehydrogenase activity decreased by 1.3 folds. This work suggests a simple inoculum strategy that could expedite the enzyme system required for xylitol production, enabling a 1.7-fold increase in productivity.