Screening Of The Guar Gum Degrading Microbes And Studies On The Production Of Enzyme

Guar gum belong to mannanm, it is a kind of thickeners which used in fracturing of oil-exploiting process and it make fracturing fluid have enough viscosity pour into formation. Fracturing fluid needs break. Biological enzyme break is an effective, safe and better specificity breaking method which take advantage of enzyme catalysis degradate thickener byβ-mannannase. This article related sampling from soil and water polluted by fracturing fluid. This thesis separated and seleted 2 strains of guar gum efficiency degrading microbes by accumulation culture , then respectively named as AS-6 and AS-12. The main research contents of this article include the following: fermentation parameters, the conditions for enzyme production and characterization of the enzyme. The results showed that:(1) AS-6 and AS-12 (inoculums size is 2%)can both produce guar gum-depolymerizing extracellular enzyme separately which able to hydrolyze the guar gum rapidly. AS-6 and AS-12 can completely degradate 50ml solution with 0.5% guar gum in 48h and 56h.(2) The best optimized condition of AS-6 as follows:0.7% guar gum as carnbon, 0.8% NH₄Cl and 1.2% peptone as nitrogen source,120r/m, 100ml medium per 250ml flask, incubate under The best optimized condition and 45℃, the highest enzyme activity as 34.38U/ml which is 2.7 times compare with optimized before; The best optimized condition of AS-12 as follows:0.7% guar gum as carnbon, 0.8% NH₄H₂PO₄ and 0.8% yeast extract as nitrogen source, initial broth pH 5.0, 100ml medium per 250ml flask, incubate under The best optimized condition and 45℃, the highest enzyme activity as 21.95U/ml which is 2.1 times compare with optimized before.(3) Under the best culture conditions, we can find degradation ability of AS-6 is better than AS-12.(4) As to the ASE-6 and ASE-12 enzyme, the optimum condition is pH 6.0 and temperature of 70℃and pH 4.5 and temperature of 55℃, ASE-6 still keep more than 70% activity at 50℃which was bitable 50℃(20min),while ASE-12 enzyme always keep more than 76% activity at 40℃which was bitable 40℃(20min). Na+, Mg²⁺, Ca²⁺, Cu²⁺, Zn²⁺, Mn²⁺ can activate the ASE-6 enzyme activity while Li+, Co²⁺, Ag²⁺, Al3+ inhibit the mannanase activity. SDS and EDTA can inhibit the enzyme activity of AS-6 strongly.Na⁺, Mg²⁺, Ca²⁺, Mn²⁺, Al³⁺ can activate the enzyme activity while Cu²⁺, Zn²⁺, Co²⁺, Ag⁺ inhibit the mannanase activity. SDS and EDTA can inhibit the enzyme activity of ASE-12 strongly while dimethylsulfoxide activate the enzyme activity.