Proceedings of International Congress on Bioactive Compounds and International Workshop on Bioactive Compounds
Proceedings of 2nd International Congress on Bioactive Compounds

Sugar alcohols, such as xylitol and arabitol, are bioactive polyalcohols obtained from sugars. Such compounds can act as sugar substitutes and generate positive effects for the consumer, such as prebiotic action and protection of teeth against caries. Although they can be obtained chemically, the biotechnological route appears as an opportunity to reduce costs and the environmental impact generated by traditional routes. Pentoses assimilating yeasts, such as Candida tropicalis, have already been reported as microorganisms capable of generating xylitol and arabitol in their metabolism, however, aspects related to production optimization, especially about arabitol, still need to be studied. In this context, this study aimed to verify the possibility of growth and production of polyalcohols by a strain of C. tropicalis isolated from sugarcane. For this, inoculation was carried out on a shaker table at 200 rpm and 35 ºC with synthetic media (10 g.L-1 of yeast extract, 20 g.L-1 of peptone and 30 g.L 1 of carbon source) with different carbon sources (xylose, glucose, L-arabinose, D-arabinose, glucose + L arabinose or Glucose + D arabinose). Then, it was evaluated the growth in a complex medium consisting of diluted hemicellulose hydrolysate of sugarcane bagasse, a renewable source of xylose (30 g.L 1), arabinose (5 g.L 1) and glucose (5 g.L 1), supplemented with yeast extract (8 g.L-1), KH2PO4 (2.6 g.L-1) and MgSO4 (0.3 g.L-1). It was noticed that, with the exception of the culture media consisting exclusively of D-arabinose, there was cell growth and consumption of carbon sources in all synthetic media. Although consumption of the carbon source was not identified in the medium containing exclusively D-arabinose, it was noticed that this pentose was consumed in the medium containing glucose + D-arabinose. It was also observed that, from the medium containing only xylose, there was production of xylitol (Yxyl,s = 0.57 ± 0.03) and arabitol (Yarab,s = 0.008 ± 0.004), a behavior that also occurred in the medium containing only L arabinose (Yxyl,s = 0.06 ± 0.03; Yarab,s = 0.31 ± 0.04) and in the medium with glucose + L arabinose (Yxyl,s = 0.06 ± 0.01; Yarab,s = 0.45 ± 0.01), confirming that there are pathway relations in the assimilation of such pentoses for the production of these polyalcohols. Regarding the growth in hemicellulose hydrolysate of, after 70 h of fermentation, all glucose, 65 % of the xylose and 40 % of the arabinose had been consumed, generating 0.71 ± 0.05 g.L 1 of arabitol (Yarab,s = 0.22 ± 0.03) and 12.9 ± 2.1 g.L-1 of xylitol (Yxyl,s = 0.45 ± 0.04). This preliminary study shows that this strain of C. tropicalis, in addition to being able to consume, form biomass and produce polyalcohols from pentoses, it can survive and generate products of interest from complex media derived from residues, such as hemicellulose hydrolysate, which has in its composition inhibitory compounds. However, it is noteworthy that studies to optimize the process are necessary as a way to increase productivity and make the process viable on larger scales and replace the chemical route.