Screening And Identification Of Microbial Deodorization Strain And Studies On Deodorization Mechanism

In recent years, with the development of livestock industry, ozone pollution has become a serious problem. The major components of stink from Livestock waste odor are ammonia and hydrogen sulfide. Although the traditional physical and chemical way to remove stink is efficient, but its high cost and hard to spread restrict development. Microbial deodorization becomes a breakthrough to resolve the issue. Therefore, screening the microorganism from nature which can deodorize effiently is meaningful and promising. It can solve smell pollution well without highly inputs.In this topic, two strains which can remove NH3 and H2S quickly are isolated from activated sludge of wastewater treatment plant. The study on deodorizing properties and deodorization mechanism is carried on and the results are as follows:(1)By the method of isolation and Screening, two strains JN-4 and AF-1 which can remove NH3 and H2S quickly are isolated from activated sludge of wastewater treatment plant.(2)According to Colony and cell morphology orbservation, physiological and biochemical identification and phylogentic analysis of 16S rDNA sequence, strain JN-4 and AF-1 are identified as Bacillus subtilis and Thiobacillus thioparus.(3)The composition of the culture medium and the condition of the culture were investigated in this paper. And sequential statistical experimental designs (Plackett-Burman, Factorial, steepest ascent and response surface method) were applied in the experimental design. The objection of the paper depicted to how to use sequential statistical designs to optimize the fermentation media for NH3 oxidizing rate in shake flask experiments, and to get the max NH3 oxidizing rate of JN-4. The best condition of culture is: 35℃, pH 7.0, 200rpm. Estimated optimum medium composition of the NH3 oxidizing rate of JN-4 was as follows: Glucose 3g, (NH4)2SO4 0.628g, NaCl 0.827g, FeSO4?7H2O 0.07g, K2HPO4 0.591g, MgSO4?7H2O 0.1g, water 1000ml. The NH3 oxidizing rate is increased by 41.91% and reaches the maximum 6102.345μg /MLSS?d as compared to 4300μg /MLSS?d.(4) In the H2S oxidation ability optimization tests of AF-1, Plackett-Burman design and orthogonal design were used. The best group of optimization tests is: T 30℃, pH 7.0, H2S 200mg/L, (NH4)2SO4 2g/L. According to this, The H2S oxidizing rate is increased by 86.1% and reaches the maximum 135.31 mg/L?d as compared to 75 mg/L?d.(5)The study on multi-paths of nitrogen metabolism of JN-4 shows that: Under aerobic condition, NH4+-N and NO2--N loss reach 98.51% and 84.50% and total nitrogen loss could reach 63.1% and 16.9%. JN-4 could reduce NO3--N into NH4--N with organic carbon source and kalium nitricum as nitrogen source. In this condition, NO3--N and total nitrogen loss could reach 96.54% and 49.6%. The NH4+-N accumulation could be transformated together with NO3--N. It shows that JN-4 could highly oxidize NH4+-N and grow with glucose carbon source and it also had aerobic denitrification ability. While under anaerobic condition, strain JN-4 could still reduce NO3--N with sodium acetate as the sole carbon source. In the cells of strain JN-4 with such multi-paths of nitrogen metabolism, coupling of heterotrophic nitrification-aerobic denitrifier is feasible and it is of value in use.(6)The study on the terminate product of oxidizing H2S of AF-1 shows that: Under aerobic condition, the strain AF-1 could converse H2S to SO42-. The content of sulfur keeps balance after conversion performance of AF-1. Almost 100% S2- was converted to SO42- in a day. This result shows AF-1 could oxidize H2S quickly from the surface.(7)According to the study on the key enzyme of nitrification and denitrification process of JN-4 and H2S oxidizing of AF-1 by using the method of molecular biology and bioinformatics, the deodorization mechanism of JN-4 and AF-1 was revealed. This result lays a foundation of constructing genetically engineered bacteria.