Microbial Community In Chinese Rice Wine Inoculated Raw Wheat Qu And Analysis Of Enzyme And Flavour Produced By Isolated Microbes

As saccharifying, leaven and aroma-producing agents in Chinese rice wine brewing, Chinses rice wine wheat Qu is called ‘bone of the wine’. Inoculated raw wheat Qu is the inheritance and development of raw wheat Qu and cooked wheat Qu and it’s also a big progress of wheat Qu-making, raw materials was used and formed a new complex microbial community structure by Aspergillus oryzae and microbes contained in crushed wheat. It is important in producing qingshuang type Chinese rice wine and is widely used in Shanghai rice wine production enterprises, but there has been no relevant report for it yet. The analysis of physiochemical indexes, microflora and isolated microbial’s properties of inoculated raw wheat Qu could be helpful of deeply understanding the nature of the inoculated raw wheat Qu and provide theoretical basis of improving wheat Qu making process by microbes and regulating rice wine’s flavour.In this paper, the physiochemical indexes of inoculated raw wheat Qu was systematically elaborated, then the single-molecule sequencing technology was employed to analyze the microflora of inoculated raw wheat Qu. Finally we analyzed the microbial’s enzyme and flavour production performance isolated from inoculated raw wheat Qu. The main results were as follows:1. The glucoamylase activity of cooked wheat Qu(963.84 mg/g·h) was significantly higher than inoculated raw wheat Qu(903.75 mg/g·h). The alpha-amylase activity(6.15 g/g·h) and acid protease activity(65.76 μg/g·min) of inoculated raw wheat Qu were 15.17% and 27.20% higher respectively than cooked wheat Qu. The flavour compounds in the inoculated raw wheat Qu were quantified by HP-SPME/GC-MS. The results showed that a total of 70 volatile flavor compounds were identified and quantified in inoculated raw wheat Qu. The top five content of all the volatile flavor compounds were 1-octene-3-ol, 2,3-butanediol, 4-Vinylguaiacol, Tetramethylpyrazine and benzene ethanol.2. The effect of DNA isolation by seven different methods were evaluated. The results showed that SDS-CTAB method has the best effect on the isolation of total DNA of wheat Qu. Then single-molecule sequencing technology was adopted to analyze the microflora of inoculated raw wheat Qu, the results showed that there exist 18 kinds of fungi, among these, Aspergillus oryzae(22.72%), Pichia fabianii(21.62%), Penicillium decumbens(8.88%) and Pichia kudriavzevii(7.18%) had a higher relative abundance. There existed 59 kinds of bacteria, among these, Weissella confusa(15.37%), Enterobacter asburiae(9.45%) and Weissella paramesenteroides(6.28%) had a higher relative abundance.3. 40 strains of microorganisms were isolated from inoculated raw wheat Qu, including 12 strains of fungi, 11 strains of yeast and 17 strains of bacteria. Through determination of the enzyme activity of cooked wheat Qu made by microbes isolated from inoculated raw wheat Qu, we found Aspergillus oryzae(≥849.9 mg/g·h), Bacillus subtilis JX6(769.2 mg/g·h) and Bacillus amyloliquefaciens JX13(694.5 mg/g·h) had the strong ability in glucoamylase production; Aspergillus oryzae(≥4.32 g/g·h), Aspergillus niger(≥3.94 g/g·h), Bacillus subtilis JX6(5.62 g/g·h) and Bacillus amyloliquefaciens JX13(8.66 g/g·h) have the strong ability in alpha-amylase production; Aspergillus oryzae(≥35.2 μg/g·min), Aspergillus fumigatus JF9(40.1 μg/g·min), Bacillus subtilis JX6(38.5 μg/g·min), Bacillus amyloliquefaciens JX13(40.3 μg/g·min), Staphylococcus xylosus JX4(33.6 μg/g·min) and Staphylococcus capitis JX17(49.6 μg/g·min) have the strong ability in acid protease production.4. Through determination of the volatile flavour compounds of cooked wheat Qu made by microbes isolated from inoculated raw wheat Qu showed that Saccharomyces cerevisiae JY5 and Candida krusei JY6 can produce high content of aromatics compounds, alcohols, esters and acids. Saccharomyces cerevisiae JY5 had the ability in producing high content of phenethyl alcohol, ethyl palmitate and guaiacol; 2,3-butanediol was mainly produced by Candida krusei JY6 and Bacillus subtilis JX6; Bacillus subtilis JX6 had the ability in producing high content of Tetramethylpyrazine; 1-octene-3-ol was mainly produced by fungi. Saccharomyces cerevisiae JY5, Acinetobacter baumannii JX8, Candida krusei JY6, Cyberlindnera fabianii JY7, Rhizomucor pusillus JF2 and Aspergillus oryzae JF3 had a higher comprehensive capacity in producing volatile flavour components.