Studies On The Breeding Of Chinese-Liquor Yeast By Protoplast Fusion And Its Characteristics

The thesis focused on the respiration deficient mutant of Maotai Liquor yeast JG3220;meantime a strain MT-14 was isolated from Maotai- Daqu embarked by Shenzhou-5 manned spacecraft;and a yeast strain RHZ-7,which has stronger ability to producing alcohol and ester,was obtained by the technology of protoplast fusion with HX-9 and MT-14.The respiration deficient mutant HX-9 was mutated by EB with Maotai Liquor yeastJG3220 and was chosen as a parental strain for fusion.The characteristics of the yeasts embarked by spacecraft were developed and 51 strains of yeasts was obtained from Maotai- Daqu embarked by Shenzhou-5 manned spacecraft .By selection,the strains which can produce more alcohol and ester MT-9, MT-14, MT-25 and JG3220 were all identified as Saccharomyces cerevisiae .Among them.MT-14 was selected as another parental strain for fusion.By the inactivated protoplast fusion method carrided out, fusants was selected through the means by TTC,and the fusant RHZ-7 was obtained which can produce 9.27% (v/v) alcohol and 0.721g/L ester.The genetic stability and the characteristics of RHZ-7 were also studied;the optimal growth and fermentation temperature were 32℃ and the optimal growth and fermentation pH were 5.0 respectively.The temal death was 53℃-54℃, alcohol tolerance was 14%,the growth pH was 3.0~8.0,fermentation pH was 3.5-6.5 and the fermentation characteristics were better than Maotai Liquor yeastJG3220. The temal death of JG3220 was 51℃-52℃,alcohol tolerance of JG3220 was 12%,the growth pH of JG3220 was 3.0~8.0,fermentation pH of JG3220 was 3.5~7.5.The sugar tolerance of RHZ-7 was better than that of JG3220 while the sugar concentration were 10%, 20%, 30%.