Short-term Adaptation Strategy Improved Xylitol Production by Candida guilliermondii on Sugarcane Bagasse Hemicellulosic Hydrolysate

In this work, we proposed a short-term adaptation strategy to improve xylitol production on sugarcane bagasse hemicellulosic hydrolysate through the maximization of Candida guilliermondii FTI 20037 tolerance to inhibitors. Hemicellulosic hydrolysate obtained by diluted acid hydrolysis (1.0% (wv(-1)) H2SO4, 1:10 solid/liquid ratio, 121 degrees C, 10 min) was concentrated up to fivefold to obtain hydrolysates with different concentration factors. Yeast was cultivated in each hydrolysate for 24-h and consecutively transferred to the subsequent more concentrated hydrolysate to obtain different adaptation degrees. Adapted cells were used as inoculum in fermentations with the same hydrolysate in which they were adapted. The performance of adapted and non-adapted yeast was compared to validate the adaptation strategy employed. The beneficial effects of adaptation were more pronounced in the hydrolysates with higher inhibitor concentration (twofold concentrated and non-treated, H2N; and fivefold concentrated and treated, H5). It improved xylose assimilation and xylitol production as well as xylitol yield and xylitol volumetric productivity in both hydrolysates. A 62.5% increase in productivity (0.24 to 0.39 gL(-1) h(-1)) and a 15.7% increase in yield (0.51 to 0.59 gg(-1)) were observed for H5 hydrolysate, while for H2N hydrolysate these increases were 54.5 and 29.6%, respectively. Yeast adaptation also improved arabinose consumption and reduced glycerol production. The reduction in glycerol production indicates a greater tolerance of adapted cells to the inhibitors present in hydrolysates. Short-term adaptation proved to be an efficient strategy to improve yeast tolerance as well as its fermentative performance on sugarcane bagasse hemicellulosic hydrolysate.