Pretreatment of swine manure containing β-lactam antibiotics with whole-cell biocatalyst to improve biogas production

Biogas is one of the most popular renewable alternatives. Large quantities of antibiotics are used for rearing livestock resulting in the presence of high levels of antibiotics in manure, inhibiting biogas production during anaerobic digestion. In this study, a novel whole-cell biocatalyst that can accelerate degradation of antibiotics was developed by displaying beta-lactamase on the cell surface of Escherichia coli. This biocatalyst showed high enzyme activity (4.93 +/- 0.77 U/g dry weight of cells) in degrading beta-lactam antibiotics and higher stability at room temperature than free beta-lactamase. Penicillin, cefamezin, and amoxicillin were completely degraded in solution by the biocatalyst within 1 h. Pretreatment of swine manure containing 50 mg/kg and 100 mg/kg of penicillin, cefamezin, and amoxicillin with the new biocatalyst enhanced methane production by 37.1% and 93.2%, respectively during anaerobic digestion. The engineered biocatalyst protected the microbial community from antibiotic inhibition and hence is conducive for the growth of methanogens. This new strategy eliminates the inhibiting effects of antibiotics on manure, increasing the methane production and therefore achieving maximum utilization of renewable energy during anaerobic digestion. This pretreatment technology provides a new idea to treat manure containing antibiotics and improve energy efficiency. (C) 2019 Elsevier Ltd. All rights reserved.