Screening And Application Of ?-aminobutyric Acid-producing Strains From Starter Of Xiecun Huangjiu

Huangjiu is a peculiar type of wine in China,and is one of the typical representatives of Oriental brewed wine.Qu is the bone of wine,to some extent,the microorganisms in Huangjiu starter determine the quality of Huangjiu.At present,the research on the microorganism of starter mostly focuses on the production of enzyme and aroma.?-aminobutyric acid?GABA?is an important functional component of Huangjiu,which has the effects of lowering blood pressure and improving brain function.It mainly comes from the brewing raw materials of Huangjiu and some microbial transformation.At present,there are few studies on GABA in Huangjiu,mainly focusing on the determination of GABA content in Huangjiu and the breeding of GABA-producing strains.However,the application of GABA-producing strains in the production of Huangjiu has not been reported.In this study,a strain with high GABA production was screened from the starter of Xiecun Huangjiu,and its tolerance and safety were studied to evaluate the application potential of the strain.The screening strain was applied to make fortified starter,and the GABA content,physical and chemical indexes,biochemical indexes were determined to evaluate the quality of the starter.The Huangjiu was brewed with fortified starter,and the GABA content,physical and chemical indexes of Huangjiu were determined to evaluate the quality of rice wine.In order to provide scientific reference for improving the quality of Huangjiu and developing functional Huangjiu by regulating microorganisms.The main conclusions of this study are as follows:?1?A total of 53 strains of bacteria and fungi were isolated fromstarter,GABA-producing strains were screened by thin-layer chromatography combined with high-phase liquid phase.10 strains with GABA-producing ability were selected,accounting for 19%of the total bacteria.Among them,the bacterial strain N5 had the highest GABA production,reaching0.78 g/L.Preliminary evaluation of N5 tolerance and safety found that N5 can withstand high temperature of 45?,8%-10%ethanol,acidic environment with pH of 4 and 25%glucose.And the strain has no hemolysis,no lysine decarboxylase activity,no arginine decarboxylase activity,no ornithine decarboxylase activity,good antibiotic sensitivity,high safety,and can be used in rice wine production.After identification,the strain N5 was identified as Bacillus subtilis.?2?Different concentrations?10²?10⁴?10⁶?10⁸?10¹00 cfu/mL?of B subtilis N5 were Inoculated in two ways,One method of addition was to inoculate N5 into starter on the day of starter making?0th day?by mixing it with the raw material.The second method was to inoculate and prepare the fortified starter by spraying on the surface of the blank starter on the0th,3rd,6th,9th,12th and 15th days after the starter making was completed.The results showed that the GABA content,saccharification force,liquefaction force and protease activity of the starter were increased by adding the strain.Among them,the GABA content of the starter sprayed at 10⁸ cfu/mL on day 0 was 10.76 mg/g,which was 88%higher than that of the unadded strain,On the 12th day of spraying 10¹00 cfu/mL,the saccharification activity was604.2U/g,which was 46%higher than that of blank starter,On the 0th day,the liquefaction power of 10¹⁰cfu/mL sprayed starter was 0.411U/g,which was 45%higher than that of blank starter.On the 3rd day,the protease activity of 10⁶cfu/mL sprayed starter was 212.4 U/g,which was 35%higher than that of blank starter.In general,the starter sprayed with 10⁸cfu/mL B subtilis N5 on the 0th day was the best in all aspects,with a GABA content of 10.76 mg/g?88%increase?,a water content of 10.52%?1%decrease?,Acidity was 0.547mmoL/L?4%decrease?,saccharification power was 511.1 U/g?23%increase?,liquefaction power was0.384 U/g?36%increase?,and protease activity was 199.5 U/g?27%increase?.In terms of the composition of microbial communities,the enrichment of the bacterial community was enhanced,the richness of the fungal community decreased,and the relative abundance ratio of some genus was affected.?3?Fortified starter was used to brew Huangjiu,and it was found that when the starter of10⁸ cfu/mL was sprayed on 0th day,the content of GABA in the brewed Huangjiu was359.8 mg/L,which was 59%higher than that of blank Huangjiu.The change of total sugar in Huangjiu with the concentration of the strain was consistent with the change of saccharification and liquefaction of Huangjiu with the concentration of the strain,On the 0th day,when the 10⁸ cfu/mL N5 was mixed,the total sugar of Huangjiu was the highest in each group,which was 36.3 g/L.On the 9th day,when the 10⁸ cfu/mL N5 was sprayed,the Huangjiu had an alcohol content of 16.7%vol,which was 16%higher than that of blank Huangjiu.On the 15th day of spraying with a strain of 10¹00 concentration,the total acidity of Huangjiu was the highest,which was 4.29 g/L.The trend of amino acid nitrogen content in Huangjiu was similar to the law of protease activity in Huangjiu,and on the 3rd day,10² cfu/mL N5 of Huangjiu amino acid nitrogen The highest content was 0.484 g/L;All indicators meet the national standards for refreshing flavor semi-dry rice wine.On the whole,the Huangjiu made by spraying 10⁸ cfu/mL cfu/mL N5 on the 0th day had the best effect in all aspects.The GABA content was 354.5 mg/L?57%increase?and the alcohol content was16.6%vol?increased 16%?,total sugar was 36.27 g/L?18%increased?,total acid was 4.16g/L?2%decreased?,amino acid nitrogen content was 0.47 g/L?7%increased?,pH was 4.34?4%increase?.?4?Through this study,the content of GABA in xiecun Huangjiu was increased,which provided scientific reference for the production practice of GABA functional Huangjiu,and also promoted the innovation and sustainable development of Huangjiu industry.