Alkaline-thermally treated penicillin V mycelial residue amendment improved the soil properties without triggering antibiotic resistance.

Penicillin V mycelial residue (PMR) is a byproduct of the pharmaceutical industry and may be disposed through land application after alkaline-thermal treatment. However, the efficacy of alkaline-thermally treated PMR in soil amelioration and the potential contamination risk caused by introduced penicillin V are poorly understood. In this study, soil pH, the contents of organic matter, available phosphorus, available potassium were measured to study the effect of alkaline-thermally treated PMR on soil fertility; the numbers of culturable microorganisms and the activities of enzymes, which not only reflect the decomposing ability of organic matter but also monitor the ecological suppression in soil ecosystem, were also investigated; moreover, the persistence of introduced penicillin V and the variation of antibiotic resistance genes (ARGs) in soil were examined to evaluate the resulting antibiotic resistance risk. The results indicated that the pH and the content of available potassium in amended soil with treated PMR profoundly improved. In addition, the culturable microorganisms and enzymes were not inhibited throughout the incubation of treated PMR in soil. The stability of treated PMR in soil relatively completed after 43 days. More importantly, the penicillin V derived by treated PMR rapidly depleted within 3 days, which suggested a relatively low environmental persistence. The treated PMR did not enrich the ARGs detected in soil, demonstrating that the addition of treated PMR might not trigger the antibiotic resistance risk in the short-term in soil. In conclusion, our results concluded that alkaline-thermally treated PMR is available for soil application.