Removal of amoxicillin and co-amoxiclav by newly isolated Stenotrophomonas maltophilia DF1

Antibiotics as micro-pollutants enter the environment through pharmaceutical effluents, human urine and faeces, and sweat and increase antibiotic resistance genes. The purpose of this study was to isolate amoxicillin (AMX) and co-amoxiclav (AMC) biodegrading bacteria from agricultural soil. From 15 isolates, Stenotrofomonas maltophilia strain DF1 (accession no. MW898434) was identified by phenotypic and molecular methods as the best degrading strain in the base mineral medium contained AMX or AMC. S. maltophilia strain DF1 was capable of removing 88.7% (w/v) of 43 ppm AMX and nearly 100% (w/v) of 15.2 ppm clavulanic acid after 72 h, which was measured by UV spectrophotometry and HPLC analysis. The maximum antibiotic biodegradation for S. maltophilia DF1 strain by one factor at a time was obtained after 72 h, without any additional carbon source, at 150 rpm shaking, the inoculum size of 5% (v/v), pH 7, and temperature 30 °C. According to the one-way ANOVA, the pH was affected on the AMX and AMC biodegradation. Optimal condition AMX and AMC biodegradation were determined by response surface method (RSM) with Design Expert12 software for three factors included inoculum level (1, 3, 5% (v/v)), pH (6.5, 7.25, and 8), and incubation time (40, 55, 70 h). Optimum degradation of AMC predicted by RSM at pH 7.12, inoculum level 4.78% (v/v), and 60.19 h. According to the results of this study, microbial degradation of AMX and AMC by S. maltophilia DF1 is a suitable strategy for the elimination of these micropollutants from aquatic media in aerobic conditions.

Graphical abstract