Screening Of Microbial Flocculant High-Producing Aspergillus Niger Strains By Atmospheric And Room Temperature Plasma And Its Application

Microbial flocculant has been widely concerned by researchers at home and abroad due to its advantages of non-toxic,high flocculability and environmental protection.However,the commercialization of microbial flocculant is limited due to its poor performance,easy degradation,difficult screening and high cost of culture medium.Room pressure plasma(ARTP)mutation strains have the advantages of rapid mutation.simple operation and genetic stability,which can be used to screen high-yield flocculating strains.At present,the random discharge of potato starch production waste in China caused serious environmental pollution.Sarch wastewater belongs to non-toxic organic nutrient wastewater.It is feasible to optimize it as flocculating microbial fermentation medium.At the same time,preparation of flocculant to treat potato wastewater can reduce cost,reduce environm ental pollution and create more economic value.In this paper,atmospheric pressure and room temperature plasma(ARTP)technique was used to treat Aspergillus niger xj strain was mutated by liquid medium shake flask primary screening,re screening and genetic stability to screen positive flocculating strains.The flocculating activity,growth state,genetic stability and growth environment tolerance of the starting strain and the mutant strain were compared to screen the high-quality strains.Using potato starch wastewater prepared by laboratory simulation as the basic culture medium,the fermentation conditions were optimized to cultivate high-quality strains to prepare flocculant for flocculation treatment of potato starch wastewater1.The optimum irradiation time of Aspergillus niger xj was 90s.416 mutants with high flocculating activity,good growth state and stable genetic stability were obtained from the initial screening of shaking flask culture.Two mutant strains A90-34 and A90-37 with high flocculating activity,good growth status and genetic stability were obtained The flocculation rates of kaolin suspension were 94.12%and 94.96%,respectively,which were increased by 26.19%and 27.03%compared with the original strain,respectively In the range of 92%-95%.2.The results showed that the most suitable carbon and nitrogen sources were glucose and urea,respectively.The flocculating activity was very sensitive when the concentration of urea was higher than or lower than 1.5 g/L.when the concentration of NaCl was more than 1%,the environm ent temperature was higher than 32?,and the pH value was lower than 5,the flocculating activity of the strain began to decline and mutated in different culture environments All the strains showed better flocculation activity and environm ental tolerance than the original straia.3.The simulated potato starch wastewater was used as the basic medium,and the fermentation was carried out in a non sterile way.The conditions of wastewater medium were optimized by response surface methodology(RSM).The results showed that the optimum conditions were stirring speed 130r/min.temperature30?,inoculation amount 4 ml,pH 7,glucose concentration 25g/L and urea concentration 1.5g/L.the flocculation rate of starch wastewater treatment was 91.48%,which was basically consistent with the theoretical value of 92.19%,which was 32.45%higher than that before optimization.The cost of wastewater culture medium is 67.99%lower than that of PDA medium for every liter of flocculant preparation The experiment shows that it is feasible to flocculate starch wastewater by cultivating Aspergillus niger with potato wastewater.