The Mechanism Of Liquid And Solid Fermentation Of Different Kinds Of Tea By Aspergillus Cristatus

Fuzhuan brick tea is a unique brick shaped black tea,which is popular among ethnic minorities in the border areas of southwest and northwest China due to its bright red color,rich mushroom aroma,full taste,and unique health benefits.It is also known as "the mysterious tea of the ancient Silk Road in China".Fuzhuan brick tea belongs to microbial post fermentation tea,and its processing technology mainly includes screening,steaming,composting,pressing,flowering,and drying.Its unique "mushroom flower aroma" is closely related to the "composting" and"flowering" in the fermentation process.Its essence is to control certain temperature and humidity conditions to promote the growth and reproduction of dominant microorganisms Aspergillus cristatus in large numbers,producing visible golden particles.Its quantity and quality are important indicators to evaluate the quality of Fuzhuan brick tea.Aspergillus cristatus is non-toxic and safe.Its metabolites in the fermentation process have good anti-inflammatory,antibacterial,lipid-lowering and antioxidant activities,which can be used as medicine or to develop health products.This paper uses fungal isolation and purification technology to obtain a strain of Aspergillus cristatus from Shaanxi Fuzhuan brick tea.Primary dark tea,oolong tea,yellow tea,green tea,red tea,and white tea were used for solid-state and liquid fermentation to identify the colony morphology and study the changes in the main active components during the liquid fermentation process.Based on metabonomics and transcriptome,the changes of complex metabolites of Aspergillus cristatus during liquid fermentation of primary dark tea,green tea and white tea were analyzed.Finally,six types of tea were used as fermentation substrates for artificial inoculation and fermentation,and the changes in the active ingredients and antioxidant activity of fermented tea were analyzed.This study provides theoretical guidance for the deep processing,utilization,and quality assurance of Fuzhuan brick tea,as well as corresponding technical support for the development and utilization of Aspergillcs cristatus.The main research results of this article are as follows:1、The changes of main active ingredients in Shaanxi Fuzhuan brick tea at different flowering stages were studied using UV spectrophotometry,high gas chromatography,and thin layer chromatography.It is found that the soluble sugar content of Fuzhuan brick tea increases first and then decreases,the contents of soluble protein,total polyphenols,free amino acids,Rha and Glc decrease on the whole,the contents of total flavone,Ara and Gal decrease first and then increase,while the content of Xyl remains unchanged.2、A dominant strain was isolated and purified from Shaanxi Fuzhuan brick tea,and combined with morphology and molecular biology,it was identified as A.cristatus.3、Using primary dark tea,oolong tea,yellow tea,green tea,red tea,and white tea extracts as raw materials,the solid and liquid fermentation of A.cristatus was carried out.The experimental results showed that A.cristatus was sexual reproduction on six solid media.After liquid fermentation,the content of soluble sugars,soluble proteins,total polyphenols,total flavonoids,and free amino acids in most of the six media significantly decreased.The types of sugar of primary dark tea and yellow tea media changed on the the fourth day,oolong tea and green tea media on the fifth day,and red tea and white tea media on the sixth day.At the same time,the content of Xyl and Glc in primary dark tea media,the content of Ara,Glc and Gal in oolong tea and white tea media,and the content of Man and Glc in yellow tea media significantly decreased after fermentation.4、Based on metabonomics and transcriptome,the changes of complex metabolites in the liquid fermentation of primary dark tea,green tea and white tea were analyzed.Research has found that carbohydrate metabolism,lipid metabolism,and amino acid metabolism are the main pathways of action of A.cristatus.5、Artificial inoculation and fermentation of six types of tea using A.cristatus.The study found that the content of soluble sugar,soluble protein,total polyphenols,total flavonoids,and free amino acids in most of the six types of tea significantly decreased after fermentation.The contents of Rha,Ara,Xyl,Man,Glc and Gal were significantly increased.Primary dark tea,green tea,and white tea have better antioxidant activity,and no aflatoxin B1,ochratoxin A,and fumatoxin B1 were detected in liquid and artificial fermented primary dark tea.