A Preliminary Study On The Fermentation Process Of Lipase Produced By Aspergillus Niger C2J6 And Its Adsorption Capacity Of Waste Mycelial Balls

Lipase is an important industrial biocatalyst.Among them,organic solvent-resistant lipase has many unique advantages in non-aqueous systems,making some new compounds（such as esters,peptides,chiral alcohols,etc.）and racemic compounds that are difficult to synthesize by traditional methods.It is an enzyme with broad application prospects in the fields of food,medicine,chemical industry,environmental protection,etc.In this thesis,aiming at the organic solvent-resistant lipase-producing bacteria,Aspergillus niger C2J6,which has been screened by the research group,the lipase production capacity of the bacteria is improved by optimizing the fermentation conditions.The waste mycelium ball is used for the treatment of environmental pollution wastewater,thus laying the foundation for the subsequent industrial application of Aspergillus niger C2J6.The specific research contents and results are as follows:First,the fermentation process of organic solvent-resistant lipase produced by Aspergillus niger C2J6was optimized,and the effects of carbon source,nitrogen source,metal ion,p H,liquid loading,inoculum on lipase activity were investigated.The optimal fermentation conditions for lipase production by the bacteria were determined by response surface optimization experiments:olive oil 2.5g/100m L,ammonium sulfate 25g/L,K₂HPO₄1.0 g/L,KH₂PO₄0.5 g/L,Mg SO₄0.3 g/L,Ca Cl₂0.1 g/L,KCl 0.5 g/L,the filling volume was 40%,the initial p H was adjusted to 5,and the lipase activity was increased from the initial7.13 u/m L to 41.36 h after incubation at 130 pm and 28℃for 36 h.u/m L,an increase of 5.8 times.Secondly,for the mycelial balls discarded after fermentation to produce lipase,after freeze-drying,the biosorption of Congo red dye simulated wastewater was carried out.It was found that Aspergillus niger C2J6 mycelial balls had a good decolorization effect on the dye Congo red.The concentration of red solution was 100 mg/L,the rotation speed was 120 rpm,and the adsorption effect was the best under the conditions of temperature20℃,the adsorption rate was up to 94.2%,and the saturated adsorption capacity was 31.58 mg/g.After the mycelial ball adsorbs the dye Congo red,it can be reused,and the adsorption rate remains above 60%after three times of use,indicating that the Aspergillus niger mycelium is a recyclable bioadsorption material.The adsorption of Congo red dye by the mycelium balls conformed to the pseudo-second-order kinetic model（R²=0.998）,indicating that the adsorption mechanism of the mycelium balls for Congo red was mainly chemical adsorption,including the biological mass transfer process that consumed energy.The Langmuir model and the Freundlich model were used to fit the isotherm data of the adsorption of Congo red by the mycelium balls,respectively.Finally,the simulated wastewater containing metallic chromium was adsorbed by the freeze-dried Aspergillus niger mycelium.The p H was 2,the Cr（VI）solution concentration was 200 mg/L,the speed was150 rpm,and the temperature was 20℃.The adsorption effect of chromium was the best,the adsorption rate was up to 97.2%,and the saturated adsorption capacity was 59.1 mg/g.The adsorption of chromium by mycelium balls conformed to the pseudo-second-order kinetic model,which indicated that the adsorption mechanism of chromium by mycelium balls was mainly chemical adsorption.The Langmuir and Freundlich models were used to fit the isotherm data of chromium adsorption by mycelium balls,respectively.It was found that the adsorption of chromium by mycelium balls was monolayer adsorption,and the Langmuir model could better express the adsorption process.