Screening of high γ- aminobutyric acid- yield yeast strains of Saccharomyces Cerevisiae and application in brewing of pear wine

Eight yeast strains which could produce high yield of γ- aminobutyric acid( GABA) and ethanol were screened from the surface of pear fruits,among which,yeast strain KS45 had the highest capability of GABA production( 1.146 g / L).Strain KS45 was then identified as Saccharomyces cerevisiae.When S.cerevisiae KS45 was cultivated in pear juice- contained culture media,it could produce high yield of GABA in anaerobic condition,which indicated that pear juice might had compounds that could stimulate S.cerevisiae KS45 to produce GABA.After S.cerevisiae KS45 was inoculated in Ya pear juice and fermented in a incubator at 30 ℃ for 10 d,pear wine with rich GABA( 2.427 g / L) was obtained.It was found that GABA production was coupled with ethanol consumption during the brewing of pear wine,and its mechanism was not clear.The final ethanol concentration of pear wine decreased significantly as the fermentation temperature increased.The volume of culture medium in the fermentor could affect the production of GABA. With increasing of the volume of culture medium,GABA concentration of the pear wine rapidly decreased,and the possible reason was that supply of oxygen was not sufficient.