Microbial Production of XYLITOL and Its Application – A Review

Xylitol is a sugar alcohol with an increasing global market with many applications and widely used in food, agricultural and pharmaceutical industries (Salli et al., 2016). It is a naturally occurring five-carbon polyol that is commercially used as a sweetener in food products. During mammalian metabolism of carbohydrate, it is a normal metabolic intermediate produced at a range of 5-15 g per day in an adult human (Winkelhausen et al., 1998). Xylitol has potential application in food industry, due to its cost and lack of availability the volume of xylitol used is small in the food industry, it is mainly used as a sweetner in confectionery (Povelainen et al., 2008). Xylitol is used in personal health products like mouthwash and toothpaste (Affleck, 2000). In pharmaceutical products xylitol is used as a sweetener or coating agent in the pharmaceutical industry (Pepper et al., 1998). The purified xylose obtained by acid hydrolysis of lignocellulosic substrate by chemical method using metal catalyst at extreme pressure and temperature is the conventional production process of xylitol. Hemicellulosic hydrolysate from biomass is used as raw material with the conversion of pentose sugars using microorganisms such as bacteria or yeast is the biotechnological alternative method. Using microorganism fermentation of the pentose sugars is an eco-friendly process that is done under mild conditions such as ambient temperature and atmospheric pressure; this avoids the purification step of xylose, which is the expensive step in conventional catalytic process (Prakasham et al., 2009). Production of xylitol by enzymatic technology is an attractive alternative to chemical and fermentation process (Rafiqu et al., 2012). Xylitol production from agricultural residues has great potential due to the presence of high xylan content in the form of hemicellulose (Ur-Rehman et al., 2015). Biotechnological production of xylitol from agricultural wastes such as rice husk (Hickert et al., 2013), corn cobs (Wei et al., 2010), soybean hull (Cortivo et al., 2018), sugar cane bagasse (Vaz de Arruda et al., 2017), sorghum bagasse (Ledezma-Orozco et al., 2018).