黄曲霉果胶酶的酶学特性及其在白玉兰落叶水解中的应用

Enzymatic Characteristics of Aspergillus flavus Pectinase and Its Application in the Hydrolysis of Fallen Leaves of Magnolia denudata

关键词:  果胶酶  酶学性质  黄曲霉  菌株分离和鉴定  落叶水解

Key words:  pectinase  enzymatic properties  Aspergillus flavus  strain isolation and identification  fallen leaves hydrolysis

摘要:

农业残余物还田能够改善土壤质量，然而微生物活性过低使腐熟进程缓慢。为了加快腐熟进程，本研究从土壤中筛选产果胶酶的菌株，并进行菌株鉴定及酶学性质分析，同时研究所产果胶酶对白玉兰(Magnolia denudata)落叶的水解作用。结果显示，从土壤中分离得到菌株TPF2-1，被鉴定为黄曲霉(Aspergillus flavus)，其所产果胶酶粗酶的酶活力为(0.63±0.02) IU/mL。以聚半乳糖醛酸为底物时，TPF2-1果胶酶粗酶的最适作用pH值为4.5，最适作用温度为50℃；在35℃保温1 h后酶活力无损失；在pH值4.0-7.0、25℃条件下保温24 h后仍残余大于90%的酶活力；1、2和5 mmol/L的Li⁺、Na⁺、Mg²⁺、K⁺、Cu²⁺、Zn²⁺和Co²⁺对TPF2-1果胶酶粗酶的酶活力均无明显抑制作用,Ca²⁺、Fe²⁺和Fe³⁺在5 mmol/L时表现出抑制作用。TPF2-1果胶酶粗酶可使白玉兰落叶水解体系中还原性物质的量提升至水解前的3.3倍。本研究结果表明黄曲霉果胶酶在树叶还田方面具有潜在的应用价值。

Abstract:

Returning crop residues to the field can improve soil quality.However,the low microbial activity hinders the decomposition process.Pectinase-producing strains were isolated from the soil to accelerate the decomposition process.The strain screened out was identified and the enzymatic properties of the pectinase produced by the strain were analyzed.Furthermore,the hydrolytic effect of the produced pectinase on the fallen leaves of Magnolia denudata was studied.The results showed that the strain isolated from the soil was identified as Aspergillus flavus TPF2-1,and the activity of its crude pectinase was (0.63±0.02) IU/mL.With polygalacturonic acid as the substrate,the crude pectinase of TPF2-1 showcased the highest activity at pH value 4.5 and 50 ℃.There was no loss of enzyme activity after incubation at 35 ℃ for 1 h.After incubation at pH value 4.0-7.0 and 25 ℃ for 24 h,the relative activity of the enzyme was still above 90%.Li⁺,Na⁺,Mg²⁺,K⁺,Cu²⁺,Zn²⁺ and Co²⁺ at concentrations of 1,2 and 5 mmol/L had no significant inhibitory effect on the activity of the crude pectinase of TPF2-1,while Ca²⁺,Fe²⁺ and Fe³⁺ only showed inhibitory effects at a concentration of 5 mmol/L.The crude pectinase of TPF2-1 increased the amount of reducing sugar in the hydrolysis system of M.denudata fallen leaves to 3.3 times that before hydrolysis.The results of this study indicate that the pectinase from A.flavus has a potential application value in the returning of plant leaves to the field.