Bioremediation is a technology that ‘treats’ environmental pollution using microbes, plants or their by-products. It helps in removing xenobiotic and recalcitrant pollutants through physical or chemical methods. Pharmaceutical industry releases large quantities of recalcitrant pharmaceutical by-products. Additionally, farming and municipal wastes contribute to pollution. Although pharmaceutical products are biologically active, they are non-biodegradable and recalcitrant in nature, which makes pharmaceutical pollution difficult to be rid of using conventional methods (1).
Furthermore, compounds such as antibiotics and hormones in the environment affect biodiversity and functioning of natural microbiota of the soil. Furthermore, pharmaceutical pollution causes a disturbance in ecological function and soil fertility (2,3). Moreover, pharmaceutical pollutants can also travel up the food chain and affect aquatic and terrestrial organisms, including humans (4). Nevertheless, researchers have explored the possibility of using biological systems in mitigating pharmaceutical pollution, especially since physio-chemical methods have failed to efficiently remove pharmaceutical waste products (5,6).
Major pharmaceutical pollutants
Pharmaceutical pollution includes raw materials, end products and by-products involved in the manufacturing of wide range of products (7). As a case in point, the table below shows type and class of various pollutants released by pharmaceutical industries.
Types of Pharmaceutical Pollutants
|Antibiotics||Hormones and steroids|
Table: List of effluents from Pharmaceutical industries (7).
Impact of pharmaceutical pollution
Excess antibiotics enter the environment either through human waste or during the manufacturing processes. Antibiotics enter the soil, municipal waters, ground waters, ultimately reaching the plants and herbivores (8). More importantly, antibiotics destroy the natural ecosystem of soil and aquatic environment and select resistant strains. Another pharmaceutical product, analgesics (painkillers and pain relievers) also affect the natural ecosystem (9). For example, Diclofenac and Ibuprofen, have been reported to have negative impacts on crops and plants, namely affecting their growth and development (10).
|Fluoxetine||Alters estradiol levels in fish and sexual dysfunction in humans.|
|Diclofenac, Ibuprofen etc.||Renal impairment of fish, birds and humans; also the death of vultures.|
|Ethinyl estradiol||Effect the fertility and development of fish, reptiles and other aquatic invertebrates.|
|Cytotoxins||Produces reproductive toxins in aquatic animals and tumours in plants.|
|Enrofloxacin and other antibiotics||Evolution of antibiotic drug-resistant pathogenic microbes leading to ineffectiveness.|
|Chlorpyrifos Atrazine||Susceptibility to Viral infections in humans and other animals decreases.|
Table: Pharmaceutical agents and their harmful effects (Source: Randhawa & Kullar, 2011).
Besides antibiotics and analgesics, hormones are the largest producers of wastes from pharmaceutical industries. Additionally, compounds such as Cyproterone Acetate, Letrozole, Steroids, Contraceptives and others are reported to have been found in wastewaters released by the pharmaceutical industries (6). These hormones are accumulated by plants which cause mutations and are also carcinogenic, hampering their growth phenotypically and genetically (11). Other worrying contaminants are metal, such as iron, chromium, lead, zinc, nickel, cadmium, found in pharmaceutical wastes in alarming levels of 0.05-11 mg/l (12). These metals, when accumulated by plants, affect water transport, nutrient uptake from the soil and the rhizosphere (13,14).
Role of microbes in bio-remediation of pharmaceutical pollution
Biological systems are efficient in converting recalcitrant and xenobiotic pharmaceutical drugs to less toxic forms or even leading to complete mineralisation. In fact, it has been reported that certain strains of microorganisms have the potential to use pharmaceutical wastes as their carbon source (15). Thus, bio-degradation of waste is vital and depends on a number of factors, such as the structure of the compound, toxicity, concentration levels, environmental conditions during degradation, an efficiency of the microbes to be used and presence of other compounds and their concentrations (16). In the case of pharmaceutical products, naturally occurring microbes have the capability of metabolizing the compounds but lack access to them as well as nutrients. This coupled with a low abundance of such strains significantly affect their remediation capabilities (17).
It has to be emphasized that pharmaceutical pollutants can be biodegraded using conventional biological technologies such as Aerobic and Anaerobic treatment, fungal treatment, bacterial treatment, phytoremediation and membrane bioreactors (18). These treatments lead to a significant reduction in Chemical oxygen demand (COD), Total Suspended Solids and also Total Dissolved Solids (TDS). Additionally, cow dung has been used in the biodegradation of pharmaceutical compounds (4)
Mode of action
The literature review showed that a wide range of organisms have been found to actively metabolize pharmaceutical products of which microbes are prominent. Thus, the table below lists species that can be used for bioremediation of pharmaceutical waste.
Type of Microorganism
|Bacteria||Mixed Bacterial Cultures,|
Clostridium sp. etc
|Phenols, Cresols, catechol, sulphates, resorcinols, suspended solids, Pentachlorophenols, Organic compounds, Diclofenac, Ibuprofen etc|
Penicillium sp. etc
|Phenols, organic and inorganic compounds etc|
tomato hairy root cultures,
|Toxic and Heavy metals, Phosphorous, Phenols etc.|
Table: Organisms capable of bioremediation of pharmaceutical pollutants (18).
Studies on microbial species in bioremediation have focused on their effect on reducing COD and Biological Oxygen Demand (BOD) removal, rather than the mode of action or the enzymes involved. Further studies have also shown higher efficiency of anaerobic reactors in treating pharmaceutical wastewater (19). For example, Rodriguez-Martinez et al. (2005) showed 90% COD in Penicillin G containing pharmaceutical wastewater was removed using Up-flow Anaerobic sludge reactor (20). In another study, anaerobic baffled reactors were used to treat ampicillin and Aureomycin wastewater, leading to 16-30% partial degradation. Additionally, for the case of analgesics, biodegradation of Diclofenac in a bioreactor is shown in a flow chart, explaining the mode of microbial action for bioremediation (21). There were also similar studies that looked at bioreactors. However, there is a lack of focus on identification of species responsible for bioremediation of specific pharmaceutical compound.
Need for optimal re-mediating mixtures
Various pharmaceutical residues have been detected in the environment, whereby these pollutants affect aquatic organisms, terrestrial organisms, humans, plants and also the microbiota of the soil. Thus, elimination and degradation of these elements are very important as they are toxic and mutagen and whereby, these can be achieved using microbes, plants and their metabolites. Further studies have been conducted on the efficiency of bioreactors in achieving COD and BOD removal, along with the degradation of pharmaceutical products. However, it is proven that anaerobic reactors efficiently re-mediate these recalcitrant compounds. This point towards a dire need for isolating species responsible for degrading specific compounds in addition to designing optimal consortium capable of a re-mediating mixture of pharmaceutical pollution.
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