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Abstracts of Recent Publications
Abstracts 1 2   

001-P.C. Abhilash, Sarah Jamil, Nandita Singh. Eco-Auditing Group, National Botanical Research Institute, Council of Scientific & Industrial Research, Rana Pratap Marg, Lucknow 226 001, Uttar Pradesh, India. Transgenic plants for enhanced biodegradation and phytoremediation of organic xenobiotics. Biotechnology Advances, 27, Issue 4, 2009, 474 - 488.

Phytoremediation - the use of plantsto clean up polluted soil and water resources - has received much attention in the last few years. Although plants have the inherent ability to detoxify xenobiotics, they generally lack the catabolic pathway for the complete degradation of these compounds compared to microorganisms. There are also concerns over the potential for the introduction of contaminants into the food chain. The question of how to dispose of plantsthat accumulate xenobiotics is also a serious concern. Hence the feasibility of phytoremediation as an approach to remediate environmental contamination is still somewhat in question. For these reasons, researchers have endeavored to engineer plants with genes that can bestow superior degradation abilities. A direct method for enhancing the efficacy of phytoremediation is to overexpress in plants the genes involved in metabolism, uptake, or transport of specific pollutants. Furthermore, the expression of suitable genes in root system enhances the rhizodegradation of highly recalcitrant compounds like PAHs, PCBs etc. Hence, the idea to amplify plant biodegradation of xenobiotics by genetic manipulation was developed, following a strategy similar to that used to develop transgenic crops. Genes from human, microbes, plants and animals are being used successfully for this venture. The introduction of these genes can be readily achieved for many plant species using Agrobacterium tumefaciens mediated planttransformation or direct DNA methods of gene transfer. One of the promising developments in transgenic technology is the insertion of multiple genes (for phase 1 metabolism (cytochrome  P450s) and phase 2 metabolism (GSH, GT etc.) for the complete degradation of the xenobiotics within the plant system. In addition to the use of transgenic plants over expressed with P450 and GST genes, various transgenic plants expressing bacterial genes can be used for the enhanced degradation and remediation of herbicides, explosives, PCBs etc. Another approach to enhance phytoremediation ability is the construction of plantsthat secrete chemical degrading enzymes into the rhizosphere. Recent studies revealed that accelerated ethylene production in response to stress induced by contaminants is  known to inhibit root growth and is considered as major limitation in improving phytoremediation efficiency. However, this can be overcome by the selective expression of bacterial ACC deaminase (which regulates ethylene levels in plants) in plantstogether with multiple genes for the different phases of xenobiotic degradation. This review examines the recent developments in use of transgenic plants for the enhanced metabolism, degradation and phytoremediation of organic xenobiotics and its future directions.

Keywords:Phytoremediation; Cytochrome P450s; Glutathione S-tranferases; Bacterial enzymes; Transgenic plants; Metabolism; Organic xenobiotics.


002-Franciscon Elisangela , Zille Andrea, Dias  uimaro Fabio, Ragagnin de Menezes Cristiano,  urrant Lucia Regina and Cavaco-Paulo Artur,Campinas State University, Department of Food Science, 13083-970 Campinas, São Paulo, Brazil. Biodegradation of textile azo dyes by a facultative Staphylococcus arlettae strain VN-11 using a sequential microaerophilic/aerobic process. International Biodeterioration & Biodegradation, 63, Issue 3, 2009, 280 – 288.

A facultative Staphylococcus arlettae bacterium, isolated from an activated sludge process in a textile industry, was able to successfully decolourize four different azo dyes under microaerophilic conditions (decolourization percentage >97%). Further aeration of the decolourized effluent was performed to promote oxidation of the degradation products. The degradation products were characterized by FT-IR and UV–vis techniques and their toxicity with respect to Daphnia magna was measured. The amine concentrations as well as the total organic carbon (TOC) levels were monitored during the biodegradation process. The presence of aromatic amine in the microaerophilic stage and its absence in the aerobic stage indicated the presence of azoreductase activity and an oxidative biodegradation process, respectively. TOC reduction was 15% in the microaerophilic stage and 70% in the aerobic stage. The results provided evidence that, using a single Staphylococcus arlettae strain in the same bioreactor, the sequential microaerophilic/aerobic stages were able to form aromatic amines by reductive break-down of the azo bond and to oxidize them into non-toxic metabolites.

Keywords:Azo dyes; Staphylococcus arlettae; Biodegradation; Textile effluents; Aromatic amines.


ENVIS CENTRE Newsletter Vol.7,Issue 3 July 2009  
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