Screening of Protease Production in Non-Saccharomyces Yeasts and Study of Its Enzymology Characteristics
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Abstract:
Non-Saccharomyces dominated in the early stages of fermentation on the natural fermentation process. Proteins are present in varying quantities in the grape and, along with polysaccharides, are responsible for increasing must and wine turbidity. Although these proteins can be eliminated with bentonite, this nonspecific process also leads to loss of aromas and compounds that influence flavor. Protease treatment, on the other hand, specifically hydrolyzes proteins and improves the clarity and stability of the wine. The smaller, more soluble peptides and amino acids generated by this enzymatic hydrolysis are also nitrogen-containing compounds. The aim of the present work was to determine the ability of non-Saccharomyces from Cabernet Sauvignonn variety to produce proteases. A strain with good capacity of producing proteases was isolated from must. After ultraviolet-microwave compound mutation, the enzyme activity increased 1.47 times. It was identified by morphology and ITS sequence analysis. The strain was indentified as Hanseniaspora uvarum and named H.uvarum XYN162. Thereafter, the proteases produced went through enzymatic evaluation, the results showed that the optimum pH was 8.0 and the proteases activity remained more than 90% in pH 7.0-8.0; the optimum temperature was 37 ℃ and stable at 35 ℃ by the analysis of thermal stability. Moreover, metal ions has a great influence on the activity, the proteases can be activated by Fe2+ and Ca2+ and inhibited by Mg2+ and Cu2+. These results showed the strain with the potential of producing proteases possesses tremendous development value.
