Xylitol production by different yeasts: Kinetic study and biosynthesis from cashew apple bagasse hydrolysate

Xylitol is a polyol with sweetening and anti-cariogenic properties and is highly relevant to the food and pharmaceutical industries. This work evaluates xylitol production by three yeasts (Candida tropicalis, Kluyveromyces marxianus CCA510, and Kluyveromyces marxianus ATCC 36907) from different carbon sources: D-xylose (medium xylose [MX]) and D-xylose plus D-glucose (medium xylose and glucose [MXG]). The potential of xylitol production from hemicellulose hydrolysate of cashew bagasse was evaluated. In MX medium, K. marxianus CCA510 was the strain that produced higher xylitol concentration (17.04 g · L⁻¹). However, K. marxianus ATCC 36907 and C. tropicalis produced 13.22 and 9.54 g · L⁻¹, respectively. On the other hand, in MXG medium, probably due to the presence of glucose as a carbon source, lower xylitol production was observed for all microorganisms: the CCA510 strain produced 13.30 g · L⁻¹ of xylitol, while C. tropicalis and ATCC 36907 produced 11.42 and 0.64 g · L⁻¹, respectively. Additionally, the production of ethanol as a secondary product was also noted. According to the results of the kinetic study, xylitol formation is associated with the growth and consumption of substrate (xylose), which is a typical behaviour of a primary metabolite for the three yeasts. Furthermore, the strain K. marxianus CCA510 was able to produce xylitol from cashew apple bagasse hydrolysate (CABH), evidencing its potential for use in bioprocesses related to biorefinery. In view of the results reported here, it was possible to clarify in detail the kinetics of xylitol production by the yeast strains evaluated, which had the ability to produce xylitol from CABH, providing added value to this agro-industrial residue.