Study On The Degradation Of Steroid Compounds By Comamonas Testosteroni

Recently, soil pollution has become the most serious problem, and pollutants bring a great harm to organism by entering food chain. Comamonas testosteroni has the ability to utilize various refractory compounds and uses steriods as a sole carbon and energy source. Therefore it plays an important role in the bioremediation of these stable compounds in the environment. Many researches are mainly focused on cloning and expression of key enzyme genes of metabolic process in Comamonas testosteroni and constructing high-effective engineering bacteria by genetic engineering technology. But the researches on using engineering bacteria for environmental bioremediation are less. So in the present work, Comamonas testosteroni(C.t) and its two genetically modified strains (P8 , Ca3) were used to test their stability and degradation abilities in different soil samples. At the same time, we detected contents of steriods and estrogen, testosterone, and cholesterol to provide theoretical basis on environmental bioremediation. The main results were as follows:1. Each strain (C.t, P8, Ca3) was cultured in 10, 20, 30, 40 and 50 days. Then the strains were utilized to degrade different concentration testosterone. The results showed that the difference of final degradation rate reached significant level between various strains. The degradation rate of P8 reached maximum, at 46 %. The optimum degrading concentration of testosterone was 100μg/mL. There were similar degradation rate between different generation strains, and the degradation rate of subculture strain was at least 72 % of the original compared to the original bacteria. It indicated that wild type strain and engineering bacteria have better degradation stability.2. Steriods in soil were degraded by three strains (C.t, P8, Ca3). There were significant difference among different treatments of soils, strains and degradation times. The average degradation rate of P8 was 38 %, 8.9 percentage points higher than C.t in different types of soil. The average degradation rate of Ca3 was 22.6 %, 3.5 percentage points higher than C.t in different vegetation soils. The average degradation rate of P8 reached maximum in different water sludge and lotus pond sludge, 40.5% and 31.6%, respectively. With the degradation time increasing, the degradation rate also raised. Different concentration of steroids in soil lead to different degradation ability of strains. It concluded that the degradation rate of Comamonas testosteroni was related to the concentration of steroids.3. HPLC was established to detect the contents of estrogen, testosterone and cholesterol in soil after degradation. It showed that the degradation rate of P8 and Ca3 were significantly stronger than C.t in rice soil, of which P8 was 29.3 % and C.t was 24.8 %, especially to estrogen. And the condition of lotus pond sludge was same to the former, of which P8 was 30.5 % and C.t was 24 %, especially to testosterone.4. The degradation experiment in field soil has been studied. It also showed that the degradation rate of P8 and Ca3 were significantly stronger than C.t. The degradation rate treated with engineering bacteria was in average field soil was significantly lower than that treated with engineering bacteria in soil adding chicken manure. The result indicated that chicken manure can be added into the soil properly and promotes engineering bacteria to degrade steroids.What we have done can form a theory foundation for Comamonas testosteroni used in the environmental bio-remediation system, and create genetic engineering strains with higher degradation ability.