A kind of exocrine yeast strain with low protease A under stress conditions and its construction method

Abstract

The invention provides a new method for regulating intra-cellular and extra-cellular secretion of proteases A under the stress condition. The regulation is realized through over-expressing of an MRL1 gene for coding a vacuolar sorting receptor during knocking-out of an allele of a protease A coding gene, that is, a PEP4 gene. With the adoption of the bred saccharomyces cerevisiae strain, the extra-cellular secretion amount of the proteases A is obviously decreased, the foam retention of draft beer can be improved, the extra-cellular enzyme activity of the proteases A is obviously lower than that of an original strain and is decreased to about 54% of that of the original strain, and meanwhile, compared with the intra-cellular enzyme activity of the original strain, the intra-cellular enzyme activity of the proteases A of the recombinant strain is not changed significantly. A new idea and a new method are provided for reduction of the extra-cellular enzyme activity of the proteases A without change of fermentation characteristics and have the guiding significance in improving the industrial yeast foam stability.

Description

Technical field:

[0001] The invention belongs to the technical field of bioengineering, and relates to the breeding of industrial microorganisms, in particular to a yeast strain suitable for low protease A secretion under stress conditions at the end of fermentation and a construction method thereof. Background technique:

[0002] During the development of pure draft beer, brewing engineers have been troubled by some quality problems related to pure draft beer, among which the foam stability of pure draft beer is particularly prominent. Since pure draft beer is not pasteurized before packaging, at the end of fermentation, the nitrogen source is insufficient, and the high alcohol and carbon dioxide concentration will create a stressful environment for the yeast, resulting in the secretion of protease A, decomposing the foam-positive protein, and reducing the beer Foam retention, which adversely affects the foam quality of pure draft beer. Therefore, improving the foam stabil...

Images