Optimization of ultrasonic parameters for effective detachment of biofilm cells in an actual drinking water distribution system

Abstract

It is important to obtain a considerable quantity of DNA from oligotrophic environments such as a drinking water distribution system (DWDS) to study microbial communities by molecular biotechnology, and DNA yield is always one of the biggest problems when performing metagenomic sequencing on drinking water samples. To obtain as many microbes as possible, ultrasound has been widely used in cell detachment, but studies on the optimal ultrasonic parameters for biofilm in DWDS have rarely been seen. The effects of three ultrasonic parameters, including power, duration, and the number of ultrasound treatments (USTs) on the selected monoculture bacteria (Pelomonas sp.) biofilm were studied first. Then the optimal values of each ultrasonic parameter were initially determined. Based on these values, three levels of each ultrasonic parameter were selected, and then an orthogonal experiment was conducted to further study drinking water biofilm, and finally the optimal ultrasonic parameters for the effective separation of biofilm cells in DWDS were determined. The results showed that the optimal ultrasonic power, duration, and the number of USTs are 13 W, 1 min, and 15, respectively. A 20-min interval is needed between two USTs. The present optimal UST, which does not lose DNA quality, can increase the amount of extractable DNA by at least 4.78 times compared to samples without UST. This study provides a pretreatment methodology for extracting more and reliable DNA from biofilm in DWDS, and can better solve the problem of DNA collection in oligotrophic environments.