This experiment was carried out to identify and select pectinolytic yeasts that have potential use as a starter culture for coffee fermentation during wet processing. The coffee fruit was fermented for 48 h at 28 °C and a sample was taken from the fermented solution and spread onto yeast extract-peptone-dextrose agar (YPDA) media and incubated at 28 °C. A total of 28 yeasts were isolated, eight of which had the ability to produce pectinase enzymes. The species of those eight yeasts were molecularly identified and confirmed. These yeasts are Wickerhamomyces anomalus (strain KNU18Y3), Saccharomycopsis fibuligera (strain KNU18Y4), Papiliotrema flavescens (strain KNU18Y5 and KNU18Y6), Pichia kudriavzevii (strain KNU18Y7 and KNU18Y8), and Saccharomyces cerevisiae (strain KNU18Y12 and KNU18Y13). The pectin degradation index of S. fibuligera (strain KNU18Y4), W. anomalus (strain KNU18Y3), and P. flavescens (strain KNU18Y6) were higher compared to the others, at 178%, 160%, and 152%, respectively. The pectinase enzyme assays were made on two growth media: coffee pulp media (CPM) and synthetic pectin media (SPM). S. fibuligera (strain KNU18Y4) and W. anomalus (strain KNU18Y3) had great potential in producing polygalacturonase (PG) and pectin lyase (PL) compared to others in both media. However, S. cerevisiae strains (KNU18Y12 and KNU18Y13) produced higher pectin methylesterase (PME). Using MEGA 6 software, the phylogenetic trees were constructed to determine the evolutionary relationship of newly identified yeasts from our experiment and previously published yeast species. The sequences of the yeasts were deposited in the National Center for Biotechnology Information (NCBI) database.
Keywords: coffee; enzymes; pectin lyase; pectin methylesterase; polygalacturonase; starter culture.