Study On Isolation-identification And Physiological Characters Of MethamidoPhos Degrading Bacteria

Two strains of methamidophos-degrading bacteria were isolated from polluted soils,they were identified as Sarcina Goodsir and Micromonospora Oerskov,and named bacteria S and bacteria M.The methamidophos-degrading bacteria strain S and strain M were cultivating seven days in culture medium with 1000mg/L methamidophos and shaking(180r/min) at 28℃,methamidophos was degraded 79.25% and 64.76% respectively.The growth curve results indicated,at each growth factors remain constant,strain S entered delay time after bing cultivated one day,entered grown logarithm long-termly two days later,entered steadily long-termly three days later,and began to decline five days later.The periods for strain M were two days,three days,four days and six days respectively.At the same time,the methamidophos degrading rates of strain S and strain M initially increased and then decreased with the growth,and the maximum methamidophos degrading rate were found in the seven days and six days respectively.The growth condition exist difference when concentration of methamidophos,pH value,temperature,the medium volume and the quantity of inoculum were difference.At the other growth factors remain constant,choose the growth increment as index to study the growth condition,the single factor tests prove that strain S and strain M grow very well in the conditions of 1500mg/L methamidophos,pH value 7.0,temperature 28℃,the medium volume 100ml and the quantity of inoculum 10%.Choose concentration of methamidophos,pH value,temperature,the medium volume and the quantity of inoculum as factors, and choose the methamidophos degrading rate as index to study the degradation capability of degrading bacterium strainS and strain M.The result indicates that the methamidophos degrading rate is the highest when the conditions of 1500mg/L methamidophos,pH value 7.0,temperature 28℃,the medium volume 100ml and the quantity of inoculum 10% by the single factor design experiment.By using the single factor test results,response surface methodology(RSM) based on a five-level five-factor central composite rotatable design of experiments was used to optimize the optimal levels of five important factors,namely temperature(X1),pH value (X2), concentration of methamidophos(X3),the medium volume(X4),the quantity of inoculum(X5). Using the quadratic regression model,the optimum concentrations of strain S and strain M were determined:temperature 28℃,pH value7.0,concentration 1500mg/L,medium volume 100mL and inoculum amount 10% respectively,the predicted yield of the methamidophos degrading rate were 73.65% and 67.01%.After enzyme extracting by Breaking Cells of degrading bacterium strainS and strain M,choose concentration of methamidophos,pH value,temperature,time and the quantity of enzyme as factors,and choose the methamidophos degrading rate as index to study the degradation capability of degrading bacterium strainS and strain M.When the conditions of 300mg/L methamidophos,pH value 6.0,temperature 35℃,time 40min and the quantity of enzyme 15%,the methamidophos degrading rate of strainS is the highest. And the conditions for strain M were 200mg/L,7.0,40℃, 30min and 25%.According to degradation conditions and influence factors of degrading-enzyme, choose temperature,pH value and the quantity of enzyme as factors for orthogonal design experiment.Without regard to interaction effects,the optimal degradation conditions of strain S were A3B1C3,temperature 45℃, pH 6.0and the quantity of enzyme 17%,besides,the degrading rate is 88.92%.And the optimal degradation conditions for strainM were 45℃,7.0 and 27%, the degrading rate is 76.56%.Application of degrading-enzyme in rice grains in laboratories,the degrading-enzyme has certain degradation to remanent methamidopho of rice grains,the test result indicate:the degrading rate of strain S was 89.09% with the proportion of degrading-enzyme and potassium phosphate buffer solution was 1:1,and the degrading rate of strain S was 85.32% with the proportion of 1:2,the degrading rate of strain S was 79.85% with the proportion of 1:4.The degrading rate of strain M was 87.96% with the proportion of degrading-enzyme and potassium phosphate buffer solution was 1:1,and the degrading rate of strain M was 78.37% with the proportion of 1:2,the degrading rate of strain M was 67.32% with the proportion of 1:4.Therefore,the degrading rate of strainS and strain M exist difference when the proportion of degrading-enzyme and potassium phosphate buffer solution were difference:1:1>1:2>1:4, the higher enzymatic concentration, the better the digradation effect.