Use of enzymes to degrade contaminants
Introduction
Bioremediation is any biotechnological process that uses microorganisms, fungi, plants or the enzymes derived from them to recover an environment altered by contaminants to its natural condition. This use of the catabolic capabilities of living beings, mostly microorganisms, is what is called bioremediation and the first reference to this term dates back to 1930, when Tausz and Donath introduced the idea.[1] Bioremediation can be used in different compounds of matter. An example of a more generalized treatment is the cleanup of oil spills by adding fertilizers with nitrates or sulfates to stimulate the reproduction of native or exogenous (introduced) bacteria and thus facilitate the decomposition of crude oil.
The use of bioremediation as a strategy has numerous advantages over chemical or physical remediation strategies. Among the advantages to be listed according to the EPA (2004)[2] are:
However, it is worth mentioning that the use of bioremediation strategies generally leads to much longer treatment periods than those of a physicochemical nature. Furthermore, through the use of biological systems, complete removal of the contaminant is not achieved but there is always a recalcitrant fraction that is not degraded in the process.[3][4] Despite these factors, bioremediation is undoubtedly the most attractive strategy due to its low cost, being environmentally friendly and the interesting cost/benefit relationship it presents for the recovery of environmental liabilities, significantly increasing the feasibility of develop it.[5][6].
In addition to the exclusive use of microorganisms, we must add the possibility of using plants (phytoremediation) and microorganisms associated with their rhizosphere (rhizoremediation). In addition to their direct role in the degradation of organic components, the use of plants has the double advantage of improving the rhizospheric microflora through their exudates and mycorrhizae, and favoring aerobic degradation by the microbial flora of the soil, thanks to the increase in the oxygen concentration that it generates. in the root zone.[7].
Another bioremediation alternative that has been on the rise in recent years is the use of composting with organic waste.[8] The use of compost or organic amendments to soil contaminated with petroleum derivatives accelerates the microbial degradation of xenobiotic organic compounds, resulting in a low-cost strategy that in turn deals with the current problem of waste generation and treatment.
Regardless of the method used to remove contamination from a soil, there are myriad factors that influence the final efficiency and costs of a bioremediation process. Among these factors, the following stand out: i) the physicochemical characteristics of the soil, including its composition, amount of nutrients, oxygen bioavailability, moisture content; ii) the amount of soil to be treated, since large quantities generally entail a very demanding infrastructure or logistics requirement, which makes its implementation more expensive; iii) the characteristics of the contaminant (both chemical structure and initial concentration as well as the final value to be reached) since the duration of the treatment and its feasibility will largely depend on the capacity to be degraded by the organisms that inhabit the soil.