Crystalline xylitol synthesis from de-oiled rice bran hydrolysate using Candida guilliermondii NCIM 3044

De-oiled rice bran (DRB) is a byproduct of rice bran oil extraction process that contains high levels of carbohydrates serving as a valuable feedstock for the production of value-added biochemicals. In this study, mild sulphuric acid (3%, v/v) mediated thermal treatment was employed as a combined pretreatment and saccharification strategy to extract the fermentable pentose and hexose sugars from DRB. As mild acid treatment was employed for sugar recovery, two different detoxification strategies viz., activated carbon (AC) adsorption and lime (Ca(OH)₂) precipitation were adopted to reduce the inhibitor compounds from the hydrolysate prior to fermentation. The results showed that AC detoxification was more effective in removing the inhibitors with marginal monosaccharides loss. Notably, fermentation by Candida guilliermondii NCIM 3044 resulted in the maximum xylitol yield and concentration of 0.59 g/g of xylose and 64.37 g/L with DRB hydrolysate in 72 h of fermentation respectively. The produced xylitol was concentrated to 148.2 g/L and subsequently crystallized. This study highlights the potential of DRB, an agro-industrial residue that could serve as a potential feedstock for xylitol synthesis fetching an economic value out of this byproduct.

The online version contains supplementary material available at 10.1007/s13197-024-06183-x.