| Ethyl carbamate(EC) is a kind of 2A carcinogen, and ethanol can promote the carcinogenicity of EC.Spirit drinks are the main source of dietary intake of EC. Reseaches on the formation and inhibit of EC in Chinese liquor is still less both in China and abroad. In this study, the formation and inhibit of EC and related key microorganisms were investigated, and it could help us to control the content of EC in fermetation process.The main results were shown as follows:(1) The content of EC was increased during stacking and fermentation process of Maotaiflavor liquor. The accumulation of EC during the stacking process was relatively less, only 12.71 μg?kg-1(dw). The main production process of EC was fermentation process in pit, which produced a total of 53.15 μg?kg-1(dw), and reached 138.19 μg?kg-1(dw). During the fermentation process, the formation rate of EC was faster along with the higher ethanol content in the fermented grains. Changes in the content of EC in Sesame-flavor fermented grains was the same as which in Maotai-flavor ermented grains. The accumulation of EC during the stacking process was 30.10 μg?kg-1(dw). During fermentation process, 233.84 μg?kg-1 EC was produced with an average production ratewhich was 3 times of the average production rate in Maotai-flavor fermanted grains, and reached to 282.90 μg?kg-1(dw).(2) The contents of cyanide, citrulline and urea in the Maotai-flavor fermented grains were reduced after the first rise trend, and up to highest when fermented for 15 days. The content of urea was the highest in these 3 precursors of EC, which was equivalent to the 10 times of citrulline and 30 times of cyanide. Changes in the content of cyanide and urea content in Sesame-flavor fermented grains were the same as the regular in Maotai-flavor fermented grains, which up to highest when fermented for 20 days. While the content of citrulline increased constantly. The content of urea was the highest and changed most. Through SPSS analysis, the content of urea and EC were significantly correlated at P < 0.01 level in both two types of Chinese liqupr. Therefore, urea was deemed to be one of the main precursors of EC during fermentation process of Chinese liquor.(3) Analysis of Miseq sequencing and network showed that argine, which is the precusor of urea and citrulline, was related to many speicies, including L. brevis, L. buchneri, L. plantarum, L. fermentum, L. casei, L. diolivorans, P. acidilactici, L. pontis, Bacillus subtilis and S. cerevisiae, Z. bailii, S. pombe, I. orientalis, etc. Microbes related to citrulline were L. brevis, L. buchneri, L. plantarum, L. fermentum, P. acidilactici, L. pontis and B. subtilis. Microbes related to urea were C. albicans, I. orientalis, Z. bailii, L. fermentum, L. plantarum and B. subtilis.(4) Microorganisms related to EC,which were screened from Maotai-flavor fermented grains were selected to carry out the experiments of arginine and urea catabolizing. Except L. diolivorans 2-10, the abilaty of L. plantarum JD19, P. acidilactici JJB1, L. fermentum JSA30, L. casei X1, L. buchneri N5 and L. pontis JSB7 to catabolize arginine was strong. S. cerevisiae C-3 could degrade arginine well but not urea. Z. bailii C-7 could degrade urea better than C-3 but not arginine. Although S. pombe C-11 couldnot degrade arginine as well as C-3 and C-7, the ability of catabolizing urea was the best of the four yeasts. I. orientalis C-16 degeaded arginine and urea not very well. |
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