Microbial Degradation of Antibiotics from Effluents

Abstract

Antibiotics are the pharmaceutically active compounds, which kill the microbes present in the host bodies and many of these compounds are many times used as nonprescription drugs and after the intake excreted out through urine or feces either as active substances or metabolites. As these antibiotics are biologically active, they may harm the ecosystem as they collect and accumulate in different sites such as groundwater, sewage system, effluents, etc. The antibiotics which are released in the wastewater cannot be removed by conventional wastewater treatment. Worldwide consumption of various active compounds is estimated to be amounting to some 100,000 tons or more per annum. The concentration of antibiotics in wastewater is found to be in the range of less than 1–150 μg/L, which may further increase by nonmedical use of antibiotics, namely in agriculture, animal feeding operations, etc. The antibiotics are broken down into other compounds or transformation products, which are the by-products that are more active than the main compounds. Due to their high polarity, they are less biodegradable and cannot be eliminated efficiently. Since these transformation products are more stable and toxic, they remain in many ecological niches for a longer period of time, when reached in the environment such as groundwater, drinking water, and soil. The prolonged presence of these products in the environment can cause antibiotic-resistant bacteria and antibiotic-resistance genes. Although the resistance genes can occur naturally, but they mostly occur through mutation and resistance from other forms. Various studies in recent times have reported that antibiotics can be degraded by bacteria or by sorption in the sludge in wastewater treatment plants. The chapter summarizes the antibiotic contamination in effluents and various approaches for their removal, including bioconversion approaches using microbes.