Exploring Fungal Species Diversity in the Premature Yeast Flocculation (PYF) of Barley Malt Using Deep Sequencing

Abstract

Premature yeast flocculation (PYF) is the early flocculation of yeast during fermentation, which causes logistical and financial hardship to the malting and brewing industries. The occurring of PYF is suspected to be caused by the fungal infection of the barley or at least in part. The aim of this study was to perform a non-culture approach to uncover the fungal diversity in PYF malt. The genomic DNA was extracted and analyzed by amplicon sequencing. A total pairs read number of 209,523 sequences was obtained and used for taxonomic classification. The dominant fungal communities on the PYF malt were obtained based on the microbial diversity analysis by species annotation. The internal transcribed spacers sequencing analysis showed a decreased number of fungal species in PYF malt. Results showed that compared with control malt, PYF malt displayed a higher abundance of Ascomycota at the phyla level, and the abundance of Candida and Gibberella was exceptionally high in two PYF malts at the genus level. The absolute abundance of Candida and Gibberella baccata at the species level was also higher in PYF malts. The fungal species diversity within the malt indicated that the fungi community diversity was greater in the control malt than in the PYF malt. Taken together, exploring the diversity of the fungal community could be useful for malt quality control and for eliminating contamination risks.