Effect of glucose:xylose ratio on xylose reductase and xylitol dehydrogenase activities from Candida guilliermondii in sugarcane bagasse hydrolysate

Abstract

The influence of glucose on xylose reductase (XR) and xylitol dehydrogenase (XDH) enzyme activity was evaluated from sugarcane bagasse hydrolysate fermentations with different glucose:xylose ratios (1:25, 1:12, 1:5 and 1:2.5) by employing an inoculum of Candida guilliermondii grown in media containing glucose, a mixture of glucose and xylose, or only xylose as carbon sources. According to the results, the glucose:xylose ratio affected positively this bioconversion and a correlation was not observed between the favourable conditions for xylitol production and the XR and XDH activities. Also, the results were influenced not only by the glucose:xylose ratio in the fermentation medium, but also by the carbon source employed in the growth medium of the inoculum. The optimum condition for xylitol production by C. guilliermondii in sugarcane bagasse hemicellulosic hydrolysate should use hydrolysate with a 1:5 glucose:xylose ratio and inoculum grown in medium containing xylose as the only carbon source.

Improvement of biotechnological xylitol production by glucose during cultive of Candida guilliermondii in sugarcane bagasse hydrolysate

“…This reduction in xylitol concentration was also observed during the cultivation of C. guilliermondii in synthetic medium (Felipe et al 1995) and in sugarcane bagasse hydrolysate Sene et al 1998), and also during the cultivation of C. tropicalis in synthetic medium (Walther et al 2001). Recently, experiments performed in our laboratories revealed that xylitol was utilized as a carbon source by C. guilliermondii for cell growth (Silva and Felipe 2006). Formation of glycerol and ethanol by-products during this metabolism was also improved by the increase in glucose:xylose ratio.…”

Xylitol production by yeasts isolated from rotting wood in the Galápagos Islands, Ecuador, and description of Cyberlindnera galapagoensis f.a., sp. nov.

“…In addition, studies have shown that xylitol prevents osteoporosis, haemolytic anaemia and acute otitis (Mussatto and Roberto 2002). Xylitol can be produced by the chemical reduction of D-xylose derived mainly from lignocellulose biomass hydrolysates (Chen et al 2010;da Silva and Chandel 2012;Mohamad et al 2015). However, the requirement for several purification steps to separate xylitol from other polyols and sugars during the chemical process increases the production cost.…”

“…-dependent xylitol dehydrogenase (XDH) (da Silva et al 1996). D-xylulose is then phosphorylated by xylulokinase (XK) to produce Dxylulose-5-phosphate, which can be converted into pyruvate via a connection between the pentose phosphate and the glycolytic pathways (Winkelhausen and Kuzmanova 1998;da Silva and Felipe 2006). The redox equilibrium between the reactions catalysed by XR and XDH favours xylitol production (Winkelhausen and Kuzmanova 1998).…”

Xylitol production from wheat straw hemicellulosic hydrolysate: hydrolysate detoxification and carbon source used for inoculum preparation

“…This last sugar was added to the medium used to grow the inoculum in order to induce the expression of enzymes necessary for xylose metabolism, like xylose reductase and xylitol dehydrogenase (16). It was expected that the growth of the cells in an inducing medium would speed up the xylitol bioproduction in the hydrolysate-based medium, since the xylose-to-xylitol bioconversion is influenced by the type and ratio of sugars present in fermentation media (18).…”