Phenotype adaptation of Kluyveromyces marxianus for enhanced conversion of biomass into xylitol

Abstract

Adaptive changes in cell characteristics are key to resolving challenges in xylitol fermentation involving biomass hydrolysate. This study aims to improve oil palm frond (OPF) hydrolysate utilization through phenotype adaptation of Kluyveromyces marxianus ATCC 36907. Phenotype adaptation was conducted through 25 successive batch cultures. Prior to batch fermentation, critical parameters including inoculum size, cell recycling and strain stability were assessed. The findings indicate that the highest xylitol production was attained with 8% inoculum size, which also led to a shorter lag phase. The adapted strain demonstrated consistent xylitol production for up to 3 cycles of batch cultures when recycled in OPF hydrolysate. Enzymatic assays showed that the adapted strain displayed increased xylose reductase activity, signifying enhanced conversion of xylose to xylitol. It exhibited improved growth and xylitol production compared to the wild-type strain. This highlights its stable and distinctive phenotype from the parental strain, achieving a 73% conversion from the initial concentration of 80 g/L. In shake flask cultures, the adapted yeast displayed more than 55% increase in xylose utilization and 45% improvement in yield compared to the wild-type. These results affirm the effectiveness of phenotype adaptation as a viable strategy to boost xylitol productivity in OPF hydrolysate.