Current Trends in Bioremediation and Biodegradation

Shweta Kulshreshtha

doi:10.4172/2155-6199.1000e114

ISSN: 2155-6199

Journal of Bioremediation & Biodegradation

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Current Trends in Bioremediation and Biodegradation

Shweta Kulshreshtha^*
Amity Institute of Biotechnology, Amity University of Rajasthan, Rajasthan, India
Corresponding Author :	Shweta Kulshreshtha Amity Institute of Biotechnology Amity University of Rajasthan, Rajasthan, India E-mail: shweta_kul17@rediffmail.com
Received: June 04, 2012; Accepted: June 06, 2012; Published: June 08, 2012
Citation: Kulshreshtha S (2012) Current Trends in Bioremediation and Biodegradation. J Bioremed Biodeg 3:e114. doi:10.4172/2155-6199.1000e114
Copyright: © 2012 Kulshreshtha S. This is an open-a ccess article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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The OMICS Publishing Group is using online manuscript submission, review and tracking systems for quality and quick review processing. Authors may submit manuscripts and track their progress through the system. OMICS is dedicated to increasing the depth of basic and advanced Life Science Research across disciplines with the ultimate aim of improving research in the related fields. OMICS is the international resource for both life scientist and professionals in related field. The journal entitled “Journal of Bioremediation and Biodegradation” publishes high quality peer-reviewed papers covering novel aspects and methods in the field of bioremediation and biodegradation. Bioremediation is also referred to as biotreatment, bioreclamation and biorestoration. It is a process that utilizes the metabolic potential of living organisms such as plants, bacteria, fungi, algae to clean up contaminated environments, to detoxify, degrade or remove environmental pollutants. This article is based on “Current trends in bioremediation or biodegradation” which is the most important topic of discussion for pollution abatement.

Organisms may be used for bioremediation of pollutants in insitu and ex-situ conditions. With in-situ techniques, the polluted site is treated in place without excavation, however, in ex-situ techniques; samples from polluted sites are collected and transferred to laboratory. In-situ and ex-situ bioremediation strategies rely on community dynamics of organisms, their development and existence, structure and function. Living organisms, used for bioremediation, may be divided in three categories:- (i) Autochthonous (indigenous) organisms, (ii) Allochthonous (non-indigenous) organisms, (iii) genetically modified organisms. The indigenous organisms are native, stable and possess ability to adapt to the environment in which they are present. These organisms have developed effective mechanisms that help them to regulate their cellular function in response to changes in its environment. The activity of these organisms can be increased by the supplementation of nutrients which support their growth and metabolism and this process is known as biostimulation. In contrast to this, non-indigenous organisms are intruder or transient, non-stable, persist in a particular environment only if adapted and can be isolated from elsewhere and brought to the contaminated site (a process called bioaugmentation). Genetic engineered organisms are modified organisms that have ability to grow even in adverse condition or in the presence of pollutants at a rapid rate and possess high affinity for their substrates.

Current bioremediation approaches are based on two principles, i.e. metabolism or absorption of xenobiotic by living organisms. The xenobiotic serves as a storehouse of carbon, energy and other macronutrients such as nitrogen, phosphorous, and sulfur. When the compound cannot serve as a source of carbon and energy due to typical molecular structure, application of co-metabolism for remediation of xenobiotic is required. This reveals that one particular microorganism alone is incapable to degrade an environmental pollutant because of lack of variety of metabolic processes, however, community (a group of diverse organisms) have diverse metabolic processes for bioremediation of a diverse range of xenobiotics. In contrast to this, one particular microbe is able to remove a xenobiotics by biosorption process in its living or dead stage. This brief review of bioremediation emphasized that microbes/living organisms have ability to degrade xenobiotics by their enzymatic machinery or absorb xenobiotic in their biomass in both in-situ and ex-situ conditions. A large number of publications, related to biodegradation and bioremediation, are continuing to be published in various environment related journals revealing the effectiveness of developed microbial communities, phytoremediation approaches, designer microbes i.e. microbes developed by recombinant DNA technology. However, very few field trials are conducted for the developed biotechnological approaches. The question is –why are these technologies not implemented or brought to the fields? What are the problems in their implementation?

Most work has tended to concentrate upon the supplementation of nutrients for the growth of microbes and bioremediation of xenobiotics. Moreover, most of the studies focused on adjusting the pH, temperature, effluent dilution and aeration which makes it impossible to bring the technology to the field. Furthermore, it is often not feasible to remediate contaminated water or soil ex-situ due to the costs involved in transportation. As far as in-situ process is concerned, it is influenced by environmental factors and pollutants that vary from site to site and the bioavailability of pollutants to the microbes. Besides, there is limited information on the response of microbial communities to environmental perturbations and the transformation/degradation of xenobiotics to both simpler and more complex molecules. There is a loop hole in the bioremediation technology, i.e. measurable or non-measurable biochemical compounds formation and favorable or unfavorable biochemical conversions that are evaluated in terms of increased or decreased toxicity. Another technological gap in bioremediation is the need of development of technologies which can be applied in non-sterile conditions, undiluted effluents and toxic xenobiotics. This is still rarely touched field of research.

Success of bioremediation strategies depends on the amenability of the pollutant to get biologically transformed; the accessibility or bioavailability of the contaminant to microorganisms; and the opportunity for optimization of biological activity. It is important to ensure that the contaminated material is suitably detoxified at the end of the treatment. Integrated studies, combining careful field evaluation of xenobiotic degradation with molecular approaches to study microbial populations involved in degradation, have already begun that helps in finding out relationship between microbial population structure and the progress of bioremediation. Recent innovative breakthroughs in molecular and ‘-omics’ technologies such as molecular profiling, ultrafast pyro-sequencing, microarrays, mass spectrometry, meta transcriptomics and metaproteomics, transcriptome and proteome analyses of entire community along with bioinformatics tools have potential to gain insights of indigenous microbial communities and their mechanism in bioremediation of environmental pollutants. To what extent the microbe itself actually contributed to the degradation process, recognizing those factors will be helpful in developing controlling and optimize the conditions to achieve a desirable result.

Another approach of waste remediation by living organism is their conversion to useful form. Recently, researchers are trying to convert waste into worth that can be sold in the market. This approach includes the conversion of industrial, agricultural waste into mushroom, single cell protein etc. In order to bring bioremediation technology to the field it is the best approach, however, it has several limitations. Biofuel, ethanol, biogas conversion requires high cost input and skilled persons. The edible items like mushroom, single cell proteins require to pass the toxicity assay to ensure safe consumption.

“Designer microbes or organisms” can be developed by Recombinant DNA technology and used to solve the problem of bioremediation. The organisms of desired characteristics can be designed, for e.g., rate-limiting steps in known metabolic pathways can be manipulated at genetic level to increase the degradation rates, or completely new metabolic pathways can be incorporated into bacterial strains for the degradation of recalcitrant compounds. The vast majority of studies related to the use of genetically modified organisms (GMO) for bioremediation -are supported by laboratory-based experimental data. However, it is problematic to distinguish GMO-specific degradation and biodegradation due to having interference with the indigenous microbial consortia. Another obstacle is highly heterogeneous distribution of the contaminants which lead to the invalid conclusions. Besides, GMO’s based bioremediation strategies are facing several non-technical problems like cost competitiveness with other technical solutions and lack of direction or motivation for use of engineered organisms. Unfortunately, the future use and development of GMOs remains cloudy because US Environmental Protection Agency’s risk-based regulatory approach continues to stifle both research and applications of engineered products in bioremediation.

Bioremediation is a promising, relatively efficient and costeffective technology for pollution abatement. Future successful field applications appear promising if hurdles can be removed. In future, GMOs can be developed with chemotaxis power that helps them to approach and degrade toxic compounds in the environment. Government should encourage the use GMOs for bioremediation due to having specific power of removing pollutants. A single technique is unable to remediate recalcitrant compounds. Results indicate that bioremediation used in conjunction with other physical and chemical treatment methodologies can effectively transform recalcitrant xenobiotics. A group of microbes called microbial consortia can be used instead of using a single microbe for bioremediation purpose. Therefore, in the future a combination of techniques/microbes can be used for bioremediation purpose. Bioremediation depends for its success on selling the results which not only provide benefit but also remediate the wastes. If results cannot be sold in the market then thinkwhether this technology is worthwhile or not to get rid of waste which would otherwise hang around us indefinitely.