Study On The Correlation Between Microbial Community And Environmental Factors And Physicochemical Properties During The Main Fermentation Period Of Medium-high Temperature Daqu

Luzhou-flavor liquor,as a famous liquor in China,has a long-term market share of over 70%,which has a significant impact on the consumption pattern of China's liquor industry.Due to the influence of traditional fermentation characteristics,the research and understanding of the microorganism community structure distribution and change rule in the process of making luzhou-flavor daqu are extremely limited.In this study,the dynamic changes of environmental factors and Physicochemical indicators in the main fermentation period?excluding the storage period of daqu,which refers to the 29d before fermentation?of luzhou-flavor daqu were analyzed.Then,high-throughput sequencing technology was applied to analyze the distribution and dynamic changes of the microbial community structure of daqu in the main fermentation period.Finally,through redundancy analysis and Pearson correlation analysis,the correlation between the environmental factors,physical and chemical indicators and microbial community structure in the main fermentation period of daqu was explored.Relevance leads to the following conclusions:?1?With the increase of time,the ambient temperature of daqu increased to the highest value,then became stable in the middle stage of fermentation,and finally decreased to stable room temperature;The surface humidity of daqu decreased gradually with the passage of fermentation time,then gradually increased and then became stable.The environmental CO₂ concentration generally shows a trend of first rising and then falling,and finally the CO₂ concentration tends to the external environmental CO₂concentration.the change of environmental O₂ concentration and CO2 concentration presents a corresponding and opposite rule;Daqu acidity generally showed a rapid rise,then slowly decreased,and finally gradually stabilized;Daqu liquefaction capacity from0 to the highest of 0.81g/g 72h,and finally stabilized at 0.6g/g_*72h;At the 0th day of fermentation,the saccharifying power was at the highest level of about 1300 mg/g_*H.With the progress of fermentation,the saccharifying power decreased significantly in the first three days,and was at the lowest level on the 5th day of fermentation,followed by a dynamic state of increase and decrease,and finally the saccharifying power was at the level of about 600 mg/g H;With the increase of fermentation time,the protease activity of daqu showed a trend of slow increase,and basically did not increase after reaching about 105 U/g in the later stage of fermentation.The changes of some indexes such as physicochemical and environmental factors basically conform to the fermentation law of Daqu.?2?In the main fermentation stage of daqu,228 bacterial genera were detected in all samples,and the five dominant genera were Weissella,Lactobacillus,norank_c<sub>Cyanobacteria,Pantoea and Leuconostoc,respectively.All samples produced 66 fungal genera and found that the three dominant genera is Thermomyces,Thermoascus and Rhizopus.?3?Redundancy analysis showed that the samples on the 0th and 1st day of fermentation had great differences with other samples;temperature was positively correlated with CO₂,humidity was positively correlated with O₂,temperature and CO₂were negatively correlated with humidity and O₂;water was positively correlated with saccharifying power,negatively correlated with liquefying power and proteinase activity,acidity was only positively correlated with water,negatively correlated with saccharifying power,proteinase activity and liquefying power.Proteinase activity was positively correlated with liquefaction power,and both of them were negatively correlated with acidity,water and saccharification power,while saccharification power was negatively correlated with other factors except water.There are close correlations between indicators and factors,and there are many positive and negative correlations between physical and chemical indicators and environmental factors,fungi and bacteria.It was found that the relationship between bacteria and humidity was the closest,followed by protease;fungi and acidity were the closest,and there was no significant correlation with oxygen and temperature;the correlation between fungi and bacteria was more complex.?4?These complex correlations all indicate that there are complex correlations among environmental factors,physicochemical indicators and microbial communities.Whether these correlations have specific biological significance besides statistical significance needs further study and discovery by scholars.