The production of bioethanol from lignocellulosic biomass remains a major
challenge due to the high xylose content that conventional ethanol-producing
yeasts, such as Saccharomyces cerevisiae, are unable to efficiently ferment.
Although S. cerevisiae is widely favored for industrial ethanol production
because of its robustness and tolerance to ethanol and fermentation inhibitors,
its incapacity to utilize xylose significantly reduces overall process efficiency. This
study focuses on exploring non-traditional yeast species capable of co-fermenting
glucose and xylose to enhance bioethanol yield. Two yeast strains were isolated
from decomposed apple samples and molecularly identified through ITS
sequencing as Meyerozyma and Lodderomyces. Fermentation was carried out
using a mixed sugar medium with a glucose-to-xylose ratio of 2:1 over a period
of 96 hours. Both strains rapidly metabolized glucose, and more than one-third
of the xylose was consumed within the first 24 hours. The resulting ethanol yields
were 0.344 g/g for Meyerozyma and 0.327 g/g for Lodderomyces, corresponding
to an approximate fermentation efficiency of 65%. In addition, these isolates
demonstrated significant tolerance to common lignocellulosic inhibitors,
including furfural and 5-hydroxymethylfurfural (HMF), at concentrations typically
encountered in pretreated biomass hydrolysates. The findings highlight, for the
first time, the ability of Meyerozyma and Lodderomyces to efficiently co-utilize
mixed sugars for ethanol production, positioning them as promising candidates
for industrial bioethanol processes. This study opens avenues for exploiting nonconventional
yeasts to improve the conversion of lignocellulosic feedstocks into
renewable fuels.