Biotransformation of lignocellulosic biomass to xylitol: an overview

Lignocellulosic biomass (LCB) stands out as an abundant, inexpensive, and promising renewable source of energy that can be used to produce fuels and value-added products. LCB comprises of majorly 3 components: cellulose, hemicellulose, and lignin. These three components can be further transformed into commercially viable and sustainable products like ethanol, xylitol, acetic acid, glutamic acid, glucuronic acid, succinic acid, and vanillin and thus can contribute significantly towards developing cost-effective integrated biorefineries. Among these, xylitol has been a tremendously increasing area of interest. With having no petrochemical alternative, xylitol turns out to be one of the highest valued products which may be produced by utilizing lignocellulosic biomass. Its large-scale production is still carried out through chemical route by dehydrogenation of xylose under high pressure and temperature. Biotechnological route is the potential substitute for chemical route as it involves milder process conditions and can utilize both industrial and agricultural wastes thereby reducing the overall production cost. However, biological scheme has not been adopted yet at the industrial scale. This review focusses on the recent advances in production of xylitol using yeasts. Special emphasis is given on pretreatment and detoxification methods, critical growth parameters, various fermentation strategies, metabolic engineering, and product recovery.