Detection Of Extracellular Hydrolase From Aspergillus Cristatus And Aspergillus Niger And Hydrolysis Of Catechin Gallates

Microbial conversion and enzymatic hydrolysis play an important role in dark tea unique quality and flavor formation.In this study,nine fungi strains were isolated from dark tea such as Fuzhuan tea,Pu'er tea,Liubao tea and Tibetan tea.Six strains such as strain FZ-2?JX?LP-5?PE?PE-I?YA can produce lipase,xylanase,cellulase,amylase and tannase.The strain LP-9 secreted and produced lipase,xylanase,cellulase,amylase,tannase and protease.Strains PE-3 and XP-5 can produce and secrete lipase,xylanase,cellulase,tannase and pectinase.The strain PE-1 and PE-3 were studied by solid-state fermentation of green tea.Strain PE-1 can produce six kinds of hydrolytic enzymes such as lipase,xylanase,cellulase,amylase,tannase and protease.Strain PE-3 can detect seven kinds of hydrolases,such as lipase,xylanase,cellulase,amylase,tannase,protease and pectinase.The activity of lipase was 67.15U/mL,the activity of tannase was 660.46U/mL and the activity of protease was 2.50U/mL,which was significantly higher than that of strain PE-3.The cellulase activity of strain PE-3 was 6.84 U/mL,the activity of amylase was 33.81U/mL,the activity of pectinase was 12.51U/mL,which was significantly higher than that of strain PE-1.The xylanase activity of strain PE-3 was 10.07U/mL,which was significantly higher than that of strain PE-1.The conditions of liquid fermentation and the conditions of solid fermentation of green tea were studied by single factor method.The culture conditions of the strain PE-1 were as follows:the water content of the green tea was 110%,the spore suspension with the amount of spore was 3-4×107/mL,the fermentation was carried out at 28? for 14 days,and the medium was extracted with 0.05M phosphate buffer.Water activity aw =0.95.The culture conditions of the strain PE-3 were as follows:the moisture content of the green tea was 30%,the amount of the spore was 3-4×104-107/mL,the fermentation was carried out at 28? for 21 days,and the mixture was extracted with 0.1M citric acid buffer.The crude enzyme was extracted by two strains of mixed fermentation and purified by ammonium sulfate fractionation.Separation and purification by dextran G-100 gel chromatography resulted in a clear protein band with a molecular weight of about 37 kDa.The purified enzyme was used to transform the ester catechins.The results of UPLC analysis showed that ECG and EGCG were transformed into EC and EGC respectively,and EGCG was better than ECG.The changes of flavor substances in the mixed fermentation of tea were determined by headspace-solid phase microextraction and gas chromatography-mass spectrometry.Five kinds of 14 kinds of substances were detected in the tea samples after inoculation.Among them,alcohols and ketones Material-based.