RESUMEN
According to the characteristics of sludge samples from full-scale wastewater treatment bioreac-tors, the essential total DNA extraction method for most environmental samples, lysozyme-SDS-phenol/ chloroform method, was modified to improve sample pretreatment, intensify cell lysis and enhance the effi-ciency of impurity removal. Obtain a general total DNA extraction method for industrial sludge samples. Such a method was applied for total DNA extraction of sludge samples from several running full-scale an- aerobic or aerobic bioreactors in Shijiazhuang, China. The results indicated that the modified method was suitable for all the sludge samples in this study, showing the satisfying generality. The extracted total DNA of all sludge samples were pure, with about 1.8 of A260/ A280 ratio. The method was also efficient; with average total DNA yield of over 0.7 mg/g and maximum yield of 0.85 mg/g. Moreover, all the extracted to- tal DNA samples could serve as templates directly to amplify 16S rDNA by PCR. The PCR products could be separated well by denaturing gradient gel electrophoresis (DGGE) and the DGGE band patterns were clear enough to be used for further analysis. All these facts indicated that the total DNA extraction method provided in this study could meet the requirements of sludge samples research, from full-scale wastewater treatment bioreactors, using molecular biology technologies.
RESUMEN
The leakage of genetically engineered microorganism(GEM) at the beginning of operation was the important content for ecological risk assessment when GEM was inoculated in a membrane bioreactor(MBR) for bioaugmentation. The effects of different operating conditions on leaking density and intercepting efficiency of GEM were investigated in a submerged microfiltration MBR at the beginning of operation. The interception characteristics were also discussed. The results showed that different operating conditions had different influences on intercepting efficiency:higher sludge concentration was profit for interception,while higher aeration intensity and flux had opposite effects on interception. When the inoculated density of GEM was 1.0?1010 CFU/mL,the leaking densities varied from 1.0?102 CFU/mL to 2.5?102 CFU/mL under different operating conditions at the beginning of operation and the maximum intercepting efficiency could be higher than 8 lg. The main factors determining intercepting efficiency at the beginning of operation were membrane module interception,sludge adsorption as well as suspended GEM transfer inhibition and their contribution shares under certain conditions were 82.3%,14.9% and 2.8%,respectively. Gel layer formation during MBR stable operation was helpful to increase intercepting efficiency. The contribution shares for GEM interception of membrane module,sludge and gel layer were 75.3%,10.7% and 14.0%,respectively,under certain conditions.