一株丝状真菌的分离及其胞外果胶酶的酶学性质研究

Isolation of a Filamentous Fugal Strain and Enzyme Property of Its Extra Cellular Pectinase

在梅雨季节采集土壤样品,采用以桔子皮粉为唯一碳源的培养基分离产果胶酶的微生物。从土壤中筛选得到12株形态各异的细菌,但在液态培养时均未能检测得到胞外果胶酶活力;得到5株丝状真菌,其中1株XYYWZSP3在液态培养5 d后,培养液中的果胶酶活力为(0.39±0.01)U/mL。在察氏培养基平板上观察可见该菌株的菌丝体为白色,菌落疏松,无色素产生。该菌株所产果胶酶的最适作用pH为4.5,最适作用温度为55℃。在pH 3.5~7.0和25℃保温24 h后,残余酶活力高于90%。在30℃下稳定,随着温度提高,酶渐渐失活,在50℃保温1 h后残余酶活力为(23.30±1.83)%。1.0 mmol/L Ca^(2+)不影响酶活力,5.0 mmol/L Ca^(2+)将酶活力降至(45.47±2.74)%。1.0,2.5,5.0 mmol/L K^(+)、Mg^(2+)、Li^(+)和Na^(+)不影响酶活力。该果胶酶可以很好地应用于香蕉果汁的脱胶,可以将香蕉果汁中的还原性物质的量增加(47.69±2.12)%,将果汁产率提高(15.66±1.12)%。

In the present study,soil samples in plum rain season were collected and micro-organisms producing pectinase were isolated on medium containing orange peel powder as sole carbon source.Twelve bacteria strains with various shapes were isolated,but none of them showed extra cellular pectinase activity under liquid cultivation.Five filamentous fugal strains were isolated,and one of them(XYYWZSP3)showed extra cellular pectinase activity of(0.39±0.01)U/mL in the culture broth.The hypha of XYYWZSP3 was white on Czapek medium plate,and the colony was loosening,with no pigment produced.The optimal pH and temperature of XYYWZSP3 pectinase were pH 4.5 and 55℃respectively.After incubation at pH 3.5 to 7.0(at 25℃)for 24 hours,the residual pectinase activity of XYYWZSP3 was higher than 90%.The XYYWZSP3 pectinase was stable at 30℃,and gradually lost activity as the increment of incubation temperature.After incubation at 50℃for one hour,the residual enzyme activity of XYYWZSP3 pectinase was(23.30±1.83)%.Ca^(2+)at 1 mmol/L did not affect the enzyme activity,but Ca^(2+)at 5.0 mmol/L reduced the enzyme activity to(45.47±2.74)%.K^(+)、Mg^(2+)、Li^(+)and Na^(+)at 1.0,2.5 and 5.0 mmol/L did not affect the enzyme activity.XYYWZSP3 pectinase functioned well in banana juice production;it increased the content of reducing material by(47.69±2.12)%and increased the yield by(15.66±1.12)%.Thus,XYYWZSP3 pectinase showed potential in fruit juice production.