Improved xylitol production by the novel inhibitor-tolerant yeast Candida tropicalis K2

Production of potential value-added products from different lignocellulosic biomass is becoming more common due to the availability of the feedstocks in abundance and the environment- friendly nature of the microbial production process. Due to the large array of its applications in the pharmaceutical and food sectors, xylitol is considered as potential value-added compound for production. In this study, organic waste samples were collected from various habitats and screened for potential yeast isolates for xylitol production. Among 124 tested isolates, Candida tropicalis K2 showed the highest potential for xylitol production as well as inhibitors tolerance (Furfural, 5-hydroxymethyl furfural and acetic acid) phenotypes. C. tropicalis K2 produced 90 g/L of xylitol in batch fermentation (100 g/L xylose supplemented with 20 g/L of glycerol as co-substrate) with the yield and productivity of 0.90 g/g and 1.5 g/L.h, respectively, at pH 5.5 and 30 degrees C temperature. Together, >10% higher xylitol yield was achieved when glycerol was used as a co-substrate with pure xylose. Moreover, with non-detoxified corncob and Albizia pod hydrolysates, C. tropicalis K2 isolate produced 0.62 and 0.69 g/g of xylitol yields and 1.04 and 0.75 g/L.h xylitol productivities, respectively. Thus, C. tropicalis K2 isolate could be considered as promising candidate for xylitol production from different lignocellulosic biomass.

Automated summary

Due to the availability of abundant feedstocks and the environmentally friendly nature of microbial production processes, the production of potential value-added products from different lignocellulosic biomass is becoming more common. In this study, a potential yeast isolate called Candida tropicalis K2 was identified for xylitol production. The isolate showed the highest potential for xylitol production and tolerance to inhibitors compared to other tested isolates. Under specific conditions, C. tropicalis K2 produced high yields of xylitol in batch fermentation, and even higher yields when glycerol was used as a co-substrate or non-detoxified hydrolysates were used. This finding suggests that C. tropicalis K2 is a promising candidate for xylitol production from various lignocellulosic biomass sources.