Mechanism Of The Unsaturated Fatty Acids Formation In The Brewing Process Of Dongjiu Liquor

In this paper, a strain of bacteria, yeast and mold from daqu and xiaoqu of Dong Jiu liquor were isolated and screened. Protease, fermenting power and saccharifying enzyme were correspondingly regarded as bacteria, yeast and mold main screening indexs with a series of traditional microbial separation methods, respectively. Besides, the genes of fatty acid dehydrogenase in the screened strains genome were analysed to research contributions of producing unsaturated fatty acids in the process of brewing, which were researched in the perspective of microbial genes. On the basis of pure culture liquid fermentation, the test groups(respectively adding extract of daqu and xiaoqu) and control groups were set up to carry out the experiments, using gas chromatography(GC) to analyse the five different kinds of unsaturated fatty acids(myristoleic acid, Palmitoleic acid, oleic acid, Linoleic acid, alpha-linolenic acid) on a daily basis to track test content. Finally, three mixed strains were under liquid fermentation in a certain inoculation proportion with Kriging agent model to optimize. The final optimized proportion was contrasted with Dong Jiu liquor to analyse the difference content of 5 kinds of unsaturated fatty acid. Consequently, the mechanism of the unsaturated fatty acids formation in the brewing process was concluded.In this chapter, daqu and xiaoqu of Dong Jiu liquor were taken as experimental materials from which a strain of bacteria, yeast and mold were isolated, screened and identified. Firstly, bacteria, yeast and mold were isolated with the traditional microbial separation methods of dilution coated plate and plate marking, and transparent circle staining method was conducted to preliminary screen bacteria and mold, then, the determination of bacterial protease and alpha amylase enzyme activity were regarded as second screening. A strain of bacteria was selected from daqu and xiaoqu, named DX-2, XX-2, respectively. Furthermore, the screened molds were named DM-4, XM-4 by measuring their saccharifying enzyme, protease as well as alpha amylase enzyme activity of mold as second screening indexs. Moreover, TTC staining method were used to screen yeast, and then measure the alcohol content of yeast fermentation, CO2 total weight loss, total acid, total ester,etc. Finally, they were named DJ-5, XJ-4. By means of morphology, molecular biology identification and construction of phylogenetic trees, the results of identification were as follow: DX-2 belonged to methyl nutritional bacillus genus, XX-2 was part of bacillus cereus, the DM-4 belonged to mrhizopus genus, XM-4 was part of slide penicillium genus. DJ-5 and XJ-4 were abnormal wickham blastocystis.Two theories about the formative pathway and mechanism of unsaturated fatty acid were presented in this chapter. The key enzyme from the traditional approach—fatty acid dehydrogenase was taken as the basis of experimental judgment. Bacterium(XX-2,DX-2), yeasts(DJ-5, XJ-4) and molds( DM-4, XM-4) were as the object strains sent to the sangon biological engineering(Shanghai) for detecting, the fatty acid dehydrogenase gene PCR amplification and analysing their presence of fatty acid dehydrogenase gene in the genome fragments. Dong Jiu distiller's yeast microbes were as research objects to analyse dehydrogenase gene fragments and synthetic mechanism of unsaturated fatty acids in the process of brewing. The results of PCR amplification indicated that the yeasts and molds existed a class of fatty acid dehydrogenase gene which had key enzyme to synthesise unsaturated fatty acid by the judgment of preliminary.Whereas, screened bacteria had not gene of fatty acid dehydrogenase.The three screened strains, bacterium(DX-2, XX-2), yeasts(DJ-5, XJ-4) and molds(DM-4, XM-4) were divided into test groups(respectively adding extract of daqu and xiaoqu) and control groups, which were carried out under pure strains liquid fermentation. The period of fermentation was 10 days, GC analysis corresponding fermented liquid was detected daily. The analysis of measurement suggested that strains with liquid fermentation obtained maximum contents unsaturated fatty acids was after 6 or 7 days.However, starting from the eighth day, the content of all kinds unsaturated fatty acid begun to show a trend of decline. As a whole, the content of unsaturated fatty acid in each strain of the test groups were relatively higher than that of corresponding control groups. Consequently, based on the comprehensive analysis of GC, the DX-2 from the bacterium, XJ-4 from yeasts and XM-4 from molds were selected as the optimal strains of mixed strains liquid fermentation.The optimal pure strains selected by aforementioned method were carried out under mixed strains liquid fermentation to create and simulate mixed microbes environment in the process of liquor brewing. Kriging agent model was employed to optimize the mix proportion. Eventually, the contents of five kinds of unsaturated fatty acid which existed in the determinate proportion of mixed strains were compared with the predictive value to conduct relative error deviation calculation. Moreover, if the content of error was controlled below 10%, it was concluded that this method was useful and optimization was feasible. Consequently, the final optimization results of test groups that add extract of daqu and xiaoqu were V?: V?:V?=1.9:1.9:6.2, V?: V?:V?=2.0: 4.9: 3.1, respectively. The final optimized proportion was used to contrast with Dong Jiu liquor to analyse the difference content of five kinds of unsaturated fatty acid with the help of gas chromatography analysis. Thus, it was revealed that the content of unsaturated fatty acid in the fermented liquid was relatively higher than Dong Jiu liquor. There maybe had several reasons, aside from the possibility of fermentation substrate in the fermentation broth and extract liquid of daqu and xiaoqu, strains maybe also made a contribution in the process of fermentation.