Screening Of Low Temperature Pectinase Producing Yeast?Optimization Of Enzyme Production Conditions And Characterization Of Enzymatic Properties

Pectinase is a kind of enzyme that can decompose pectin.According to the characteristics of substrate and catalytic mechanism,Pectinase mainly includes polygalacturonase(PG),pectin esterase(PE)and pectin lyase(PL).Pectinase plays an important role in many industries,such as fruit juice,fruit wine processing,vegetable juice extraction,alcohol fermentation,feed addition,wood preservation,hemp degumming,cotton fabric scouring and so on.At present,Pectinase mainly comes from filamentous fungus Aspergillus Niger,and the optimum temperature of Pectinase is about 40 ?.For fruit juice,wine processing and other industries,low-temperature Pectinase has the advantages of reducing energy consumption and reducing process links.At present,the special low-temperature Pectinase used in fruit juice processing is still very rare,and the corresponding enzyme-producing strains are rarely studied.In this paper,the low temperature Pectinase producing strain was screened and identified,and the enzyme production conditions were optimized by single factor variables,and then the enzymatic properties of the crude enzyme produced by the strain were characterized.After primary screening and re-screening from frozen grape samples,a strain producing low temperature Pectinase was isolated and named PPY-1.After morphological and 5.8s rDNA sequence alignment analysis,it was preliminarily identified that the strain belonged to Saccharomyces cerevisiae.The optimum growth temperature and enzyme production temperature of the strain were 15 ? and 15 ?,respectively.the optimal carbon and nitrogen sources of enzyme production medium were grape skin and yeast powder,respectively.Fe2+ had a great promoting effect on enzyme production.Under the above fermentation conditions,the enzyme yield reached 5.4U/mL after 36 hours of culture.The optimum reaction temperature of the enzyme was 15 ? and the optimum pH value of the enzyme was 5.0.Manganese ion promoted the enzyme activity,and magnesium ion had a strong inhibitory effect on the enzyme activity.The crude enzyme produced by the strain maintained more than 90% activity in the range of pH3.5~6.5(2 hours)and more than 95% in the range of 5-45 ?(2 hours).The crude enzyme produced by the strain had high catalytic activity for pectin with different esterification degrees,Carboxymethyl cellulose,soluble starch,PGA,Xylan and so on.The above results show that the yeast strain and its Pectinase have good low temperature tolerance,acid tolerance,and a wide range of substrate,so it has great application potential in fruit juice,fruit wine processing,alcohol fermentation and other fields.