Screening Of Very-High-Gravity Fermentation Yeast And Optimization Of Alcohol Production

According to the metabolism pathway of yeast, this article focus on the study of alcohol high gravity fermentation factors such as: the screening of high production strains, nutrient condition and stressing factors, optimum fermentation condition, pilot plant trail and kinetic study of pilot trail. Result is reported as following:1. UV and NTG mutant YT253 is screened from monoploid YT16, with selecting index hexokinase and ergosterol has increased 200% and 75% respectively. YT253 can produce 13.8% with CO2lost 34.2. (23.2% and 23% higher than parents strain) at 1:2.0 water ratio, 30℃, 60h.Mating between inspiration deficient of YT253 and a high temperature tolerance strain No. 30 ( which can grow at 45℃) is implemented. YT316 is selected from 126 mated strains which can produce 13.9% alcohol at 35 ℃ in60h.2. Fermentation conditions of YT316 has been studied: such as batch-feeding, nitrogen adding, O2, pH, fermentation temperature, inorganism iron (surpher, patesium, zinc, calsium and sodium), organic acid, CO2 and alcohol toxin releasing.3. Plackeet-Burman design and respon-surface-analysis is employed to optium 12 fermentation fators. Progressing formular of optium condition is:Y=16.20+0.40Xi+0.30X2+0.4625X3-1.4438X12-1.1688X22-H).2125XiX3+0.1875X1X3-1.6438X3*Optium condition of YT316 is: water / material 1:1.8, 60℃ pretreat 20min, 90-95℃ liquifies 60min, no sacchification, peching rate 10%, pH=5.0, 10u/g acidfied proteinase, 50rpm shaker, 37'C fermentation for 60h. optium condition can get 16.3% (v/v) alcohol with utilization rate 90.56% (16.5% and 6.5% higher than traditional processing).4. 1000L pilot plant trail is implented with 1:1.8 (material:water) ratio, 90-95℃ cooking, 37℃ fermentate for 60-70h; 16.4% (v/v) alcohol is got with 1% residue sugar and 90% starch utilization rate. YT316 is a fast producer which can ferment 90% of total sugar in 48h.5. Kinetic Study of YT316 fermentation in 1000L fermentor is impelent. The model of YT316 pilot plant trail is listed as following, these formular can mimic the fermentation process perfactly.The inavation point of this paper is:1. Use quantity analysis of hexokinase and ergosterol as indexes to direct the screen of UV and NTG mutant;2. According of the theoratic of glucose inhibition, low concentration and feeding of sugar processing is selected;3. Brabender viscometer is used to analysis geltinlization curve of com starch, a 60℃ pretreatment processing is selected;4. PB design and responding surface analysis is used to selected the optimum condition.