Study On Alcoholic Fermentation Temperature Resistant Strain Screening

At present,China's alcohol industry has two major production methods,that is the chemical synthesis and the grain brewing.As the main raw material of ethylene for the chemical synthesis comes from petroleum processing,this method is significantly affected by oil resources and prices.While the grain brewing method,namely using yeast for fermentation of glucose in food,the materials are easily obtained as renewable resources,is the main method of ethanol production in China.In order to solve the problem of alcoholic fermentation rate declining and production cost raising under the hot summer weather conditions in Shijiazhuang,we use the alcohol yeast strain FY-23?Saccharomy cesecrecisia FY-23?,derived from the North China Pharmaceutical Huasheng Co.,Ltd.,as the starting strain,through a series of yeast cell protoplast mutation and several rounds screening,eventually,a new type high temperature resistant yeast strain FY-23-8#is obtained.The main content of our completed works are as follows:Complete the testing of various basic physiology performance of the starting strain FY-23,including:thallus size,proliferation state,growth curve,lethal temperature,alcohol resistance.The results show that the FY-23 is a production strain of good stability,but the temperature resistance is poor.Generally,when temperature is over 36?,its growth and alcoholic fermentation capacity decrease significantly.Under the condition of 38?,using the protoplast UV Mutation Technique,through TTC plate initial screening,CO₂ producing and alcohol fermentation rescreening method to obtain the expected temperature resistance mutant.Experimental results show that under conditions of pH 7.5,30?,25min treatment of 15 g/L snail enzyme,the protoplast formation rate reached 95.5%and the high osmosis regeneration rate reached 5.1%.Though 15s treatment of UV mutagen,protoplast mortality rate reached 80%.After TTC plate preliminary screening under the condition of 38?,nine primary strains of vigorous growth are obtained,through times of rescreening,the'performance of strain#8 is particularly prominent,it's named as FY-23-8#.Complete the laboratory scale comparison test of ethanol fermentation between strain FY-23-8#and strain FY-23.Under the same condition of 38?,the alcoholic fermentation conversion rate of FY-23-8#reached 44.8%,compared with 39.8%of the control group,increases by 12.6%;the alcohol yield reached 12.5%?V/V?,increase by 34.4%comparing with 9.3%?V/V?of the control group.After 10 times subculture of the FY-23-8#strain,the amount of CO2 produced is basically stable,indicating that the mutant strain can be stably inherited.Physiological characteristics tests showed that the optimum temperature range is 35?³8?.Growth curve shows bacterial cells reached stationary phase at time of 14h,the ethanol tolerance is slightly higher than the reference strain,and it can grow well in 20%glucose,the sugar tolerance meets the production requirement.The orthogonal tests show that the optimum process conditions are:ratio of material to water is 1:3;DE value is greater than 95%,reducing sugar concentration is 20%,pH 5.0,38?,and the inoculation volume is 10%,at the end of fermentation alcohol content reach11.4%.50L pilot scale experiments show that the difference of fermentation ethanol yield between FY-23-8#at 38?and the control strain FY-23 at 32?is insignificant,which are both more than 11%?V/V?.In summary,through the above mentioned work,the FY-23-8#mutant strain obtained can grow and ferment alcohol well at 38?,has good temperature resistance and other stable genetic performance,which make it a potential production strain in hot climates.