Evaluation of xylitol production using corncob hemicellulosic hydrolysate by combining tetrabutylammonium hydroxide extraction with dilute acid hydrolysis

• Combined tetrabutylammonium hydroxide extraction and acid hydrolysis was applied.
• Corncob hydrolysate was used in xylitol production by Candida tropicalis.
• High xylitol yield and productivity of 2.45 g/(L h) was achieved.
• Response surface methodology was applied to optimize the process.

In this paper, we produced hemicellulosic hydrolysate from corncob by tetrabutylammonium hydroxide (TBAH) extraction and dilute acid hydrolysis combined, further evaluating the feasibility of the resultant corncob hemicellulosic hydrolysate used in xylitol production by Candida tropicalis. Optimized conditions for corncob hemicellulose extraction by TBAH was obtained via response surface methodology: time of 90 min, temperature of 60 °C, liquid/solid ratio of 12 (v/w), and TBAH concentration of 55%, resulting in a hemicellulose extraction of 80.07% under these conditions. The FT-IR spectrum of the extracted corncob hemicellulose is consistent with that of birchwood hemicellulose and exhibits specific absorbance of hemicelluloses at 1380, 1168, 1050, and 900 cm−1. In addition, we found that C. tropicalis can ferment the resulting corncob hemicellulosic hydrolysate with pH adjustment and activated charcoal treatment leading to a high xylitol yield and productivity of 0.77 g/g and 2.45 g/(L h), respectively.