ABSTRACT
Recombinant plasmid pICG was constructed by replacing the internal fragment of a-acetohydroxyacid synthase (AHAS) gene (ILV2) with a copy of gamma-glutamylcysteine synthetase gene (GSH1) and copper chelatin gene (CUP1) from the industrial brewing yeast strain YSF31. YSF31 was transformed with plasmid pICG linearized by Kpn I and Pst I. A recombinant strain with high-glutathione and low-diacetyl production was selected. The results of fermentation in 100-L bioreactor showed that the lagering time of beer produced for recombinant strain T2 was shortened by 3 days and the shelf life of the beer was prolonged about 50%. It may be more acceptable for the commercial application, as it does not contain foreign DNA.
Subject(s)
Acetolactate Synthase , Genetics , Metabolism , Beer , Microbiology , Cloning, Molecular , Diacetyl , Metabolism , Fermentation , Gene Expression Regulation, Fungal , Glutamate-Cysteine Ligase , Genetics , Metabolism , Glutathione , Metallothionein , Genetics , Metabolism , Organisms, Genetically Modified , Genetics , Saccharomyces cerevisiae , Genetics , Metabolism , Saccharomyces cerevisiae Proteins , Genetics , MetabolismABSTRACT
The yeast fusant ZFF-28, which is high in biomass production and rich in selenium, was constructed after mutagenesis and protoplasts fusion between yeast strains. The total selenium content of ZFF-28 is 1.8 and 1.0 times higher than that of the parental strains Saccharomyces cerevisiae ZY-67 and Saccharomyces kluyveri SZY-198 respectively. Using single factor tests and a L16(4(3) x 2(1)) orthogonal design, the cultivation conditions was optimized as: 50mL culture in 250mL shake flasks in molasses containing 6% sugar and 60microg/mL Se at 28 degree C for 25h at 220 r/min, with the initial pH adjusted to 6.0 - 6.5. Under the optimized conditions, the biomass (dry weight) reached 8.2g/L and the Se content of the cells reached 2050microg/g, with organic and inorganic Se contents being 91% and 9% respectively.
Subject(s)
Biomass , Hydrogen-Ion Concentration , Saccharomyces , Genetics , Metabolism , Saccharomyces cerevisiae , Genetics , Metabolism , Selenium , Metabolism , Selenium Compounds , MetabolismABSTRACT
Self-cloning is a favorable technique in modification of industrial microorganisms especially food microorganisms because of its bio-safety. A survey and outlook of research in breeding of self-cloning industrial brewing yeast were introduced in this study.
ABSTRACT
The enzyme activity of ?- Acetolactate Decaroboxylases (ALDC) from different microbes was studied, the results demonstrated that it was quite different among them. There were diversities of their enzyme reaction velocities. It was clear that the enzyme activity was affected by the pH of the enzyme reaction system, for example, the optimum pH of ALDC from Lactococcus lactis was 6. 6, while for Aerobacter Aerogenes it was 5. 8. Addition leucine,valine and isoleucine into enzyme reaction system obviously affected the enzyme activity of ALDC from different microbes.