Research On Characteristics Of Thermoactinomyces In Moutai-flavor Daqu

Daqu which is made up of wheat,barley,pea and other main raw materials has a large shape and contains many kinds of microbes and enzymes.According to the controlling production temperature,Daqu can be divided into high temperature Daqu,medium temperature Daqu and low temperature Daqu.Moutai-flavor Daqu belongs to high temperature Daqu and mainly is used for the production of Moutai-flavor liquor.Using high temperature to product Daqu is crucial to forming the unique style of Moutai-flavor liquor.The research combined the technology of producting Daqu of Moutai-flavor liquor,taking Moutai-flavor Daqu as experimental material,designing sample treatment methods,selecting appropriate diluents,inhibitors and medium in order to isolate and purify Thermoactinomyces from the high temperature Daqu.And next identifying the isolated microbes through morphological identification,SEM observation,Fluorescence microscope observation,physiological and biochemical characteristics and molecular biological methods.Next on the one hand,the research studied some culture conditions such as temperature,water content,pH and alcohol content whether they has impact on the growth of Thermoactinomyces or not.On the other hand,the research explored the some characteristics of the isolated microbes including culture characteristics in different media,growth curve determination,enzyme production characteristics and analysis of volatile components of solid-state fermenting products.The main results were as follows:?1?The research took the system method and 5 strains of which colony morphology was similar to Thermoactinomyces were isolated from Moutai-flavor Daqu.They were respectively: first using CaCO₃ to enrich culture Thermoactinomyces,next disposing the sample with heatmoisture treatment,using CMC?2.5 g/L?as diluent,and next adding novobiocin?30 mg/L?and nystatin?20 mg/L?as mixed culture inhibitor,taking GTY medium as the seperating medium,setting 45?⁵0? as culture temperature.The identification results were: FBKL4.005,FBKL4.006,FBKL4.009 were identified as Thermoactinomyces thalpohillus;FBKL4.007 was identified as Thermoactinomyces sacchari and FBKL4.008 was identified as Laceyella sacchari.?2?The research studied the effects of culture conditions on the growth of the 5 strains.The results showed that: The optimum pH for the growth of 5 strains was 7;The optimum growth temperature of FBKL4.005 was 50?,and the optimum growth temperature of the other strains was 45?;The optimum water content for the growth of FBKL4.007 was 40%,and the other 4 strains were suitable for the growth of water content of 50%;FBKL4.008 had the strongest tolerance to alcohol and the alcohol tolerance was 20%,FBKL4.006 and FBKL4.009 had the weakest tolerance to alcohol.?3?The results of the study on the basic characteristics of Thermoactinomyces showed that: The growth and colony characteristics of 5 strains were different in different kinds of media.5 strains of Thermoactinomyces entered logarithmic growth phase after 8 h or 10 h;after 18 h,all of them entered the stable phase;and after 22 h entered into the decline stage.The 5 strains of Thermoactinomyces had stronger ability to produce pectinase,but the activity of cellulase,lipase and acid protease showed weaker.The relationship between the production of enzyme and the growth of 5 strains was coupling while in wheat bran medium.The analysis of volatile components of the solid-state fermentation of 5 strains showed that the volatile components mainly included alcohols,aldehydes,ketones,alkanes,esters and terpenes.In the sensory evaluation showed butter flavor and off flavor,at the same time the research detected the butterflavor volatile products,they were pyrazines,and also detected the off flavor volatile product,it was geosmin.