Screening Of Thermotolerant Yeast Strains And Applied Research Ethanol Fermentation Of Molasses

With the global energy emergency fuel ethanol as a green renewable clean energy, countries in the world attach great importance to. Fuel ethanol in wine yeast (Saccharomyces cerevisiae) for the production of strains for fermentation production. Tolerance to low temperature of the fermentation bacteria, you need to consume large amounts of cooling water, ethanol distillation recycling energy consumption, ethanol production process by adding sulfuric acid to prevent bacterial contamination, is the urgent problem of the ethanol fermentation process. Breeding high-temperature high-yield ethanol fermentation strains has important application value.Xishuangbanna orchard soil samples as a source, a high-temperature filter out high-yield ethanol yeast strains K. marxianus Z7. The strain was grown at30℃to-48℃, the optimum growth temperature of42℃. According to the colonies of the strains and cell morphology, physiological and biochemical characteristics were identified initially identified K. marxianus Z7strains belonging to Kluyveromyces (Kluyveromyces). Combined D1/D2+ITS district of molecular phylogenetic analysis identified the K. marxianus Z7strain the Kluyveromyces the Marx Crewe-dimensional yeast (Kluyveromyces marxianus) and named for the K. marxianus Z7.In this study, high temperature resistant yeast K. marxianus Z7screened following ethanol fermentation research.(1) Isolates K.marxianus Z7glucose and sucrose fermentation characteristics, and to establish the optimal fermentation conditions. This strain using glucose as the substrate fermentation optimal fermentation conditions were:42℃or under, pH6,10%sugar concentration. Under this condition,12h of fermentation, the ethanol conversion rate3.38g/1/h24when the ethanol conversion rate was1.73g/1ethanol production reached a maximum value of41.1g/1, is80.6%of the theoretical value. Sucrose optimum fermentation conditions fermented for24hours ethanol production reached the highest value of45.77g/1, ethanol conversion rate of1.91g/1,89.8%of the theoretical conversion rate.(2) K.marxianus Z7strains of sugar cane molasses fermentation characteristics. Through a variety of single-factor:molasses Brix, yeast powder added amount, the amount of nitrogen sources add, the amount of phosphate add, Mg2+, K2+, Cu2+add volume, to consider the strain of optimum fermentation and nutrient conditions. Orthogonal experiment to determine the significance of various factors. Significant descending:Brix> yeast extract>nitrogen source> K+>Cu2+> Mg2+>phosphate. The results show that the optimum strain molasses fermentation conditions were:20BX°molasses brix;0.5%yeast extract added amount;0.05%nitrogen source;0.02%of Mg2+and0.04%K+.This condition K.marxianus Z7strains fermentation and were compared with the Angel Yeast (Saccharomyces cerevisiae A), S. cerevisiae A fermentation temperature of30℃. In the fermentation24h K.marxianus Z7strain ethanol production reached the highest value of60.2g/1,92.4%of the theoretical value. S. cerevisiae A strain to60.0g/1, lower than the experimental strains. In fermentation of the K.marxianu Z7strains12h s, ethanol conversion rate10.5g/1/h and1.21times the S. cerevisiae A strain.(3) K.marxianus Z7strains immobilized on ethanol fermentation. Sodium alginate immobilized the K.marxianus Z7strains the optimum fermentation conditions with the original strain and immobilized S. cerevisiae A strains comparison. The strains of immobilized K.marxianus Z7of fermentation24h when ethanol production reached its highest point, the yield was44.6g/l higher than original strain (41.1gl), and S. cerevisiae strains A44.7g/1, the two strains ethanol production, ethanol The conversion rate is the same, both1.86g/1. Immobilized K.marxianus Z7strains the molasses fermentation ethanol production compared with the S. cerevisiae A strain. The two strains were fermented for24h highest ethanol yield strain K.marxianus Z760.9g/l,93.5%of the theoretical value, and the S. cerevisiae strain A60.4g/l and92.8%of the theoretical value, low in the experimental strains. The K.marxianus Z7strain rate of fermentation, fermentation24h to3.33g/l, higher than the S. cerevisiae A strain2.52g/l. The experimental K.marxianus Z7strains with potential for industrial fermentation.