Barley Husk Degraded by MH1 Induced Premature Yeast Flocculation.

Premature yeast flocculation (PYF) is one of the pivotal problems affecting beer flavor and production. PYF is induced by certain non-starch polysaccharides produced by the degradation of malted barley husks upon the growth of contaminated microorganisms, such as In this research, the formation mechanism of PYF was uncovered by investigating the secretome of MH1 inoculated to the barley husk. The polysaccharide extract of degraded husk was ultrafiltrated into four fractions and characterized by the minimum PYF concentration, molecular mass distribution, monosaccharide composition, and potential. Among the four fractions, the high-molecular-weight polysaccharide fraction had the highest content of uronic acid and the most negative potential, which contributed to the most severe PYF phenomenon. In addition, the PYF yeast showed a more negative potential than the control yeast during the small-scale brewing process. This is aligned to the negatively charged polysaccharides potentially bonded to the surface of yeast cells through the calcium cation in the same fermentation system, which results in rapid flocculation and precipitation. Approximately 12% of the 214 proteins identified in the MH1 secretome were hemicellulases, which substantially interpreted the mechanism of polysaccharides inducing PYF yeast during beer brewing.