Degradation of Nevirapine and Trimethoprim from Aqueous Solutions using Selected Microorganisms
Abstract
Together with pharmaceutical residues, personal care products encompassing prescription drugs, fragrances, and cosmetics have been detected in groundwater and other aquatic environments, hence compromising the quality of water. Their classification as micropollutants is due to their antibacterial resistance potential, persistence, and ecotoxicity. Biodegradation has been identified as a potential mechanism in their removal. The focus of this study focus was bioaugmentation; (Bacillus subtilis, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeroginosa) to enhance the degradation of Nevirapine and Trimethoprim in model aqueous solutions. A liquid chromatography-tandem mass spectrometer (LC-MS/MS) was used to determine the pharmaceuticals. The efficacy of the bacterial strains to degrade selected drugs was evaluated by making the two drugs the sole source of energy and carbon. From the experimental data, the highest percentage biodegradation was recorded; Pseudomonas aeroginosa (86 %) and Staphylococcus aureus (79 %) for TMP and NVP respectively.
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Introduction
The occurrence of pharmaceutical residues in surface waters is an emerging environmental concern (Zhou, Lutovsky, Andaker, Gough, & Ferguson, 2013). The main sources of these residues include wastewaters from hospitals, drug production facilities as well as agriculture. Owing to growth in population, coupled with the emergence of new ailments, many pharmaceutical products are being manufactured today for the protection of humans and animals. Low concentrations of pharmaceutical residues have deleterious effects on aquatic biota. It also has adverse effects on human health (Wang, Hu, & Wang, 2018).
Some pharmaceutical residues are partially broken down by animals. However, most are eliminated in their original forms. The residual pharmaceutical compounds in animal manure can easily penetrate the terrestrial environment and are readily transported into aquatic environs through direct runoff and leaching. Recent studies have also revealed that many pharmaceuticals are degraded partially since most municipal wastewater treatment plants are not designed for the removal of pharmaceuticals (Chefetz, Mualem, & Ben-Ari, 2008).
Trimethoprim and Nevirapine are widely used antibiotics and anti-retroviral respectively. Different techniques have been used for their removal including biological, physical, and chemical processes. Amongst the physicochemical methods adopted include, sorption by special materials, advanced oxidation processes (AOP), and photodegradation (Basha et al., 2010; Chefetz et al., 2008; Klavarioti, Mantzavinos, & Kassinos, 2009). While biodegradation of trimethoprim and nevirapine has been reported in several publications and reviews, only a few microalgae, bacterial and fungal species have been found to degrade them (Göbel, McArdell, Joss, Siegrist, & Giger, 2007). Of great consideration in the removal of organic micropollutants from wastewater are their water solubility, tendency to volatilize, hydrophobicity, and biodegradability.
The dynamics of bacterial populations exposed to different concentrations of antibiotics have been examined and modeled in relation to the minimum inhibitory concentration (MIC). Without drugs, the growth rate of cells is higher than the death rate, and thus a bacterial population always grows. When drug concentration increases, as long as the concentration remains below the MIC, the growth rate is higher than the death rate and thus a population still grows, albeit at a slower rate. When the drug concentration increases further and reaches the MIC, the growth rate becomes equal to the death rate, and the population size is maintained at a constant level. Only at drug concentrations above the MIC does a bacterial population decline (Magiorakos et al., 2011). In this study pure cultures of Escherichia coli, Pseudomonas aeroginosa, Bacillus subtilis, and Staphylococcus aureus commonly found in the water were used to evaluate the biodegradability of Nevirapine and Trimethoprim.
Conclusion
Results show that Pseudomonas aeroginosa, Escherichia coli, Staphylococcus aureus, and Bacillus subtilis can degrade biodegrade. Highest percentage biodegradation were recorded for Pseudomonas aeroginosa 0.5 mg/ml (86 %) and Staphylococcus aureus 1.5 mg/ml (79 %), TMP and NVP respectively. Of late, the necessity for fresh biotechnological tools to get rid of pharmaceuticals from the environment, with less harm and negative impacts, has risen. Utilizing indigenous microorganisms can be a viable solution to tackle this menace. Based on the experimental data, it is evident that higher pharmaceutical concentrations have extreme effects on the microorganisms.
