Characterization of yeast mutant strains for starter culture in Arabica coffee fermentation

Abstract

Arabica coffee is the most popular and best-selling type of coffee. During coffee fermentation, microorganisms are essential for the production of metabolites and volatile compounds that affect coffee flavor quality. This work aimed to study the mutation, selection, and characterization of the Wickerhamomyces anomalus strain YWP1-3 as a starter culture to enhance the flavor quality of Arabica coffee. The results revealed that six mutants could produce relatively high levels of the pectinase enzyme on pectin agar media and exhibited high activity levels, ranging from 332.35 to 415.88 U/ml in mucilage broth. Strains UV22-2, UV22-3, UV41-1 and UV32-1 displayed higher levels of amylase activity than did the wild type. The UV22-2 and UV22-3 mutants exhibited the highest pectin degradation indices of 49.22% and 45.97%, respectively, and displayed significantly enhanced growth rates in nitrogen yeast base media supplemented with various sugars; thus, these mutants were evaluated for their ability to serve as a starter for fermentation of Arabica coffee. The cupping scores of coffees derived from UV22-2 and UV22-3 were 83.5 ± 1.5 and 82.0 ± 2.14, respectively. The volatile compounds in the roasted coffee fermented by UV22-2 were analyzed by GC‒MS, which revealed higher levels of furfuryl alcohol and furfuryl acetate than did the other samples. These findings suggested that UV22-2 could be an influential starter culture for Arabica coffee fermentation.