The high-molecular weight polycyclic aromatic hydrocarbons(PAHs) pyrene and typical long chain alkane nhexadecane are both difficult to degrade. In this study, n-hexadecane and pyrene degrading strain Rhodococcus sp. ...The high-molecular weight polycyclic aromatic hydrocarbons(PAHs) pyrene and typical long chain alkane nhexadecane are both difficult to degrade. In this study, n-hexadecane and pyrene degrading strain Rhodococcus sp. T1 was isolated from oil contaminated soil. Strain T1 could remove 90.81% n-hexadecane(2 vol%) and 42.79% pyrene(200 mg·L^(-1)) as a single carbon within 5 days, respectively. Comparatively, the degradation of pyrene increased to 60.63%, but the degradation of n-hexadecane decreased to 87.55% when these compounds were mixed. Additionally, identification and analysis of degradation metabolites of Rhodococcus sp. T1 in the above experiments showed that there were significant changes in alanine, methylamine, citric acid and heptadecanoic acid between sole and dual substrate degradation. The optimal conditions for degradation were then determined based on analysis of the pH, salinity, additional nutrient sources and liquid surface activity.Under the optimal conditions of pH 7.0, 35 °C, 0.5% NaCl, 5 mg·L^(-1) of yeast extract and 90 mg·L^(-1) of surfactant,the degradation increased in single or dual carbon sources. To our knowledge, this is the first study to discuss metabolite changes in Rhodococcus sp. T1 using sole substrate and dual substrate to enhance the long-chain alkanes and PAHs degradation potential.展开更多
Inducing expression and the reaction characteristic of nitrile hydratase （NHase） from Rhodococcus sp. SHZ-1 were investigated. The results showed that the expression of NHase was greatly enhanced with the cooperatio...Inducing expression and the reaction characteristic of nitrile hydratase （NHase） from Rhodococcus sp. SHZ-1 were investigated. The results showed that the expression of NHase was greatly enhanced with the cooperation of acrylonitrile and ammonium chloride as inducer in the medium and the specific activity of NHase was increased of 44%. Then the temperature, pH, concentration of acrylonitrile and acrylamide were evaluated, which affected the activity and reaction characteristic of NHase. It was found that the temperature and concentration of acrylarnide were the most important factors for the catalyzation of NHase. The optimal catalysis temperature of NHase from Rhodococcus sp. SHZ-1 was 30℃, and the activation energy of the hydration of NHase was 90.2kJ·mol^-1 in the temperature range from 5℃ to 30℃. Kmof NHase was 0.095mol·L^-1 using acrylonitrile（AN） as substrate, and NHase activity was inhibited seriously when acrylonitrile concentration was up to 40g·L^-1, the substrate inhibition constant Ki is 0.283mol·L^-1. Moreover, the NHase from Rhodococcus sp. SHZ-1 had very strong tolerance to acrylamide, in which the final concentration of acrylamide reached to 642g·L^-1 and the residual activity of NHase still maintained 8.6% of the initial enzyme activity.展开更多
基金Supported by the National Basic Research Program of China("973" Program:2014CB745100)the National Natural Science Foundation of China(21576197)Tianjin Key Research&Development Program(16YFXTSF00460)
文摘The high-molecular weight polycyclic aromatic hydrocarbons(PAHs) pyrene and typical long chain alkane nhexadecane are both difficult to degrade. In this study, n-hexadecane and pyrene degrading strain Rhodococcus sp. T1 was isolated from oil contaminated soil. Strain T1 could remove 90.81% n-hexadecane(2 vol%) and 42.79% pyrene(200 mg·L^(-1)) as a single carbon within 5 days, respectively. Comparatively, the degradation of pyrene increased to 60.63%, but the degradation of n-hexadecane decreased to 87.55% when these compounds were mixed. Additionally, identification and analysis of degradation metabolites of Rhodococcus sp. T1 in the above experiments showed that there were significant changes in alanine, methylamine, citric acid and heptadecanoic acid between sole and dual substrate degradation. The optimal conditions for degradation were then determined based on analysis of the pH, salinity, additional nutrient sources and liquid surface activity.Under the optimal conditions of pH 7.0, 35 °C, 0.5% NaCl, 5 mg·L^(-1) of yeast extract and 90 mg·L^(-1) of surfactant,the degradation increased in single or dual carbon sources. To our knowledge, this is the first study to discuss metabolite changes in Rhodococcus sp. T1 using sole substrate and dual substrate to enhance the long-chain alkanes and PAHs degradation potential.
基金Supported by the National Natural Science Foundation of China （No.20466002）, the Program for New Century Excellent Talents in University （NCET-04-089） and the Key Research Projects in the Uygur Autonomous Region of Xinjiang （No.200332109）.
文摘Inducing expression and the reaction characteristic of nitrile hydratase （NHase） from Rhodococcus sp. SHZ-1 were investigated. The results showed that the expression of NHase was greatly enhanced with the cooperation of acrylonitrile and ammonium chloride as inducer in the medium and the specific activity of NHase was increased of 44%. Then the temperature, pH, concentration of acrylonitrile and acrylamide were evaluated, which affected the activity and reaction characteristic of NHase. It was found that the temperature and concentration of acrylarnide were the most important factors for the catalyzation of NHase. The optimal catalysis temperature of NHase from Rhodococcus sp. SHZ-1 was 30℃, and the activation energy of the hydration of NHase was 90.2kJ·mol^-1 in the temperature range from 5℃ to 30℃. Kmof NHase was 0.095mol·L^-1 using acrylonitrile（AN） as substrate, and NHase activity was inhibited seriously when acrylonitrile concentration was up to 40g·L^-1, the substrate inhibition constant Ki is 0.283mol·L^-1. Moreover, the NHase from Rhodococcus sp. SHZ-1 had very strong tolerance to acrylamide, in which the final concentration of acrylamide reached to 642g·L^-1 and the residual activity of NHase still maintained 8.6% of the initial enzyme activity.
