Biodegradation
The breakdown of matter, whether chemical contaminants or organic matter, that is achieved through the use of microbial metabolic processing.
Biodegradation can act as an alternative to the potentially harmful physical or chemical breakdown of waste. Biodegradative microbes may also be used within bioremediation to help mediate chemical waste, following improper disposal, in an effort to reduce chemical pollution.
What is biodegradation?
What are some applications of biodegradation?
Polymer Recycling
Microbial communities can be used to help degrade polymers, such as plastic waste, into reusable forms.
Synthetic Detergent Degradation
Microbes can be used to help remove harmful chemical surfactants from wastewater streams.
Pesticide Degradation
Microbes can degrade chemical contaminants, such as xenobiotics from pesticides, from treated soils.
Degradation of Petroleum Hydrocarbons from Oil
Microbes can help degrade components of crude oil, such as selected hydrocarbons, for bioremediation of aquatic systems following oil spills.
What are the environmental impacts of chemical and physical waste?
Deterioration of Ecosystems
Improper disposal of hazardous chemical waste from industrial settings can lead to deterioration of ecosystems through pollution, contamination, and bioaccumulation. These chemical wastes are improperly disposed of when appropriate processing hasn't taken place, or there is leaching of these chemicals into the surrounding soils (Dubey 2024). This results in the introduction of persistent pollutants like heavy metals or persistent organic pollutants (POCs) into surrounding wildlife, impacting fertility and health, as well as contaminating soils and thus food sources. The lasting impact of this damage is a decrease in total biodiversity of surrounding ecosystems from decreased soil fertility, bioaccumulation within plants, and potential eutrophication (Dubey 2024). The presence of non-degradable plastic waste also poses a threat to ecosystems, as its persistence causes it to accumulate in organisms like aquatic life. Plastic waste can also act as a carrier for POCs, thus introducing these compounds to ecosystems through soil leaching (Dey 2023).
Human health & Groundwater Contamination
Contamination from domestic solid waste sources has negative impacts on surrounding communities through an increased rate of disease incidence. Solid wastes like cardboards, plastics, and food waste can attract vectors for disease like rodents and flies when these wastes accumulate near communities, increasing exposure to infectious diseases like diarrheal disease, leptospirosis, cholera, and more (Dehghani 2021). Public health investigations of individuals residing near chemical waste disposal sites show an increased incidence of systemic disease when there is contamination of groundwater systems through leaching processes, thus impacting drinking water. Exposure to hazardous chemicals from waste contamination can lead to infertility, developmental disability, neurological effects, anemia, leukemia, and more, depending on the concentration of specific chemicals (Buffler 1985).
Air Pollution
Significant air pollution is caused by the incineration of plastic waste, releasing greenhouse gases and noxious fumes into the atmosphere. Atmospheric accumulation of these noxious fumes can have disastrous impacts on the environment as well as human health (Ngay 2016). Volatile organic compounds and persistent organic pollutants are released along with other harmful chemicals in noxious fumes, contributing to increased concentration of carcinogens and neurotoxic impact, as well as the release of ground-level ozone, causing smog formation (Bello 2021). Increased smog formation and release of particulate matter with plastic incineration not only increases pulmonary disease incidence, but also contributes to the greenhouse effect and effectively causes climate change and global warming over time (Gaffney 2009).
Biodegradation Mighty Microbes
Pseudomonas putida has been shown to have the ability to act as a biocatalyst for the hydrolysis of PET, a common aromatic hydrocarbon within plastics. Polymer hydrolysis degrades PET, and the use of P. putida in this process can assist in its depolymerization (Brandenberg 2022). Depolymerization by P. putida occurs through its natural ability to produce hydrolase through metabolic pathways, and this organism can also be successfully genetically engineered to improve efficiency (Brandenberg 2022). Pseudomonas species can also degrade low-density polythene (LDPE), another popular polymer associated with plastics, through metabolic processing. This occurs through biofilm formation and subsequent enzymatic solubilization (Kyaw 2012). P. putida is also known to be flexible, tolerant, and easily genetically engineered, making it applicable to degrade a wider range of plastic polymers than other chemical degradation processes or microbes capable of biodegradation (Li 2019).
Pseudomonas putida
Biodegradation of plastics and dyes
Rhodococcus spp.
The genus Rhodoccus contains a wide range of catabolic diversity which aids in it's ability to succesfully degrade a number of organic compounds, as well has being able to assist in bioremediation processes. Rhodoccoci are generally more tolerable and persistent within the enviornment, making them suitable for degradation of chemical waste streams and for bioremediation of chemical waste in aquatic systems (Larkin 2006). This is also aided by a capacity for Rhodococcus species to utilize generally toxic substrates and biotransform volalite chemical compounds found in chemical waste streams (Larkin 2006). Rhodococcus species are able to biotransform these compounds due to their production of metabolic dioxygenases as well as their physiological tolerance. Physiological attributes that confer these abilities is their capacity to form highly tolerant biosurfactancts, which can adhere to oil-droplets and degrade them in bioremediation of oil spills (Allen 2005).
Biodegradation of volatile chemical compounds
Acinetobacter spp.
Acinetobacter species are unique in their ability to biodegrade a wide range of pharmaceutical compounds that would otherwise contaminate wastewater streams and leach into sources of drinking water. Pharmaceutical compounds, like antibiotics (e.g., sulfadiazine and sulfamethazine), can be degraded via Acinetobacter spp. due to the products of their metabolic pathways mineralizing these antibiotics out of solution (Wang 2017). Acinetobacter also has the capacity to degrade components of crude oil when immobilized as well. This is due to Acinetobacter spp.'s ability to not only tolerate absorption of crude oil, but also upregulate and accumulate degradative enzymes when concentrations of crude oil (e.g., tetradecane) increase (Chen 2015). Acinetobacter has been proven to successfully degrade both inorganic and organic chemical contaminants alike, such as xenobiotics, halogens, oil sludge, phosphates, and heavy metals. These contaminants would otherwise have lasting impacts when ecosystems are exposed via contaminated wastewater streams (Abdel-El-Haleem 2003).
