Comparison of enzymatic properties, fermentation characteristics, and differences in non-volatile organic acids and volatiles in the solid-state fermentation of Baijiu by five strains of different non-Saccharomyces species

In this study, five non- Saccharomyces strains of different species, Wickerhamomyces anomalus (Wa27), Hanseniaspora uvarum (Hu8), Pichia kudriavzevii (Pk2), Pichia kluyveri (Pkl3), and Pichia guilliermondii (Pg6), were investigated for their fermentation of Chinese Baiju with the aim of enhancing the levels of volatile and non-volatile compounds. Wa27 strain demonstrated the highest β-glucosidase and esterase activities, while Hu8 strain had better cellulase, protease, and pectinase activities. These five strains have good alcohol tolerance but low tolerance to acid and high temperature. Wa27 strain showed outstanding performance in producing compounds such as ethyl acetate, ethyl esters, and higher alcohols, among other. The Pk2 and Pkl3 strains of two Pichia spp. also showed relatively high content of ethyl acetate in fermented grains, with the latter significantly increasing the levels of acids such as lactic acid and volatile fatty acids. In contrast, Pg6, another Pichia sp., increased the content of benzenoid compounds, such as phenethyl alcohol, likely due to its high level of amino acid nitrogen. Sensory evaluation of Baijiu obtained through distillation verified the ability of several non- Saccharomyces yeasts species to improve the quality of Baijiu, especially Wa27 strain. Biofortification during the fermentation process contributes to the overall quality of Baijiu.