Microbiology and Biochemistry of Pesticides Biodegradation

Abstract

Pesticides are chemicals used in agriculture, forestry, and, to some extent, public health. As effective as they can be, due to the limited biodegradability and toxicity of some of them, they can also have negative environmental and health impacts. Pesticide biodegradation is important because it can help mitigate the negative effects of pesticides. Many types of microorganisms, including bacteria, fungi, and algae, can degrade pesticides; microorganisms are able to bioremediate pesticides using diverse metabolic pathways where enzymatic degradation plays a crucial role in achieving chemical transformation of the pesticides. The growing concern about the environmental and health impacts of pesticides is pushing the industry of these products to develop more sustainable alternatives, such as high biodegradable chemicals. The degradative properties of microorganisms could be fully exploited using the advances in genetic engineering and biotechnology, paving the way for more effective bioremediation strategies, new technologies, and novel applications. The purpose of the current review is to discuss the microorganisms that have demonstrated their capacity to degrade pesticides and those categorized by the World Health Organization as important for the impact they may have on human health. A comprehensive list of microorganisms is presented, and some metabolic pathways and enzymes for pesticide degradation and the genetics behind this process are discussed. Due to the high number of microorganisms known to be capable of degrading pesticides and the low number of metabolic pathways that are fully described for this purpose, more research must be conducted in this field, and more enzymes and genes are yet to be discovered with the possibility of finding more efficient metabolic pathways for pesticide biodegradation.

The function of microbial enzymes in breaking down soil contaminated with pesticides: a review

“…Herbicide compounds discovered in soil include 2,4-dichlorophenoxyacetic acid (2,4-D), dalapon, simazine, atrazine, prometryn, trifluralin, and sodium trichloroacetate (NaTCA). [ 7 , 13 , 15 , 16 ] Table 2 provided brief information on the highlighted pesticides, including the characteristics, pesticide group, mode of action, and WHO toxicity rankings. To note, some of them are multifunctional pesticides, for example, HCN and 2,4-D, which are utilized not only as insecticides and herbicides, but also as plant-growth hormone regulators [ 3 , 13 , 17 ].…”

“…Bacterial species discovered to be capable of pesticide degradation often belong to the genera Flavobacterium , Burkholderia , Arthrobacter , Azotobacter , and Pseudomonas [ 5 , 12 , 18 , 24 , 28 , 29 ]. Once these biotas are released to the soil, they are capable of quickly developing and they breakdown particular pesticide compounds that serve as carbon and energy source to these soil microorganisms, opening the way for the remediation of pesticide-contaminated sites [ 9 , 15 , 18 , 30 ]. Furthermore, white rot fungus, Auricularia auricula , Phanerochaete chrysosporium , and Dichomitus squalens are examples of pesticide-degrading fungi [ 5 , 26 ].…”

“…Microbial degradation includes the processes of oxidation of parent compounds and the subsequent generation of carbon dioxide and water with the release of energy, as well as the production of certain additional byproducts [ 11 , 22 , 25 ]. The process meanwhile supplies carbon and energy for microbial growth and reproduction [ 15 , 22 ]. Moreover, each degradation stage is mediated by a specific enzyme produced either by the degrading cell or extracellular enzymes [ 9 , 22 ].…”

“…The lack of an adequate enzyme might be the cause of pesticide persistence [ 5 ]. Because microorganisms destroy pollutant for the purpose of survival, and organisms accomplish their jobs only under favorable environmental circumstances that meet their demands, certain modifications could be made to encourage the degrading-organisms to degrade the pesticide at a quicker rate in a restricted period of time [ 15 , 22 ]. To activate the degradation processes of bacteria and fungi, for example, fertilizer or oxygen must be supplied to the pollutant-containing medium.…”

“…Generally, the use of purified or free enzymes bypasses the limitations associated with the use of whole microorganisms, such as the comparatively slow process of bioremediation, which may take weeks to months for the microbes to accomplish substantive remediation [ 12 , 27 , 36 ]. Furthermore, the performance of microbial remediation is limited to many growth parameters and ideal growth circumstances, such as moisture, pH, temperature, pollutant chemical composition, and redox potential [ 12 , 15 , 22 ].…”