Browsing by Author "Awadhesh K. Shukla"

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Bio-filtration of trichloroethylene using diazotrophic bacterial community
(Elsevier Ltd, 2010) Awadhesh K. Shukla; Pranjali Vishwakarma; R.S. Singh; S.N. Upadhyay; Suresh K. Dubey
Biodegradation of TCE was studied in a biofilter packed with wood charcoal and inoculated with diazotrophic bacterial community isolated from local soil. Steady state TCE removal efficiencies higher than 85% were observed up to inlet load of 2.866 g m-3 h-1. The maximum elimination capacity of 5.31 gm-3 h-1 was observed at an inlet load of more than 7.90 g m-3 h-1. The biofilter was sensitive to fluctuations in the process conditions but could easily recover its performance after 10 days shutdown. Almost constant and small pressure drop per unit length and very negligible compaction was observed during the whole experimental period. The molecular analyses such as RT-PCR and gene sequencing revealed the presence of functionally active Azospirillum species in the biofilm. © 2009 Elsevier Ltd. All rights reserved.
Biodegradation of trichloroethylene (TCE) by methanotrophic community
(2009) Awadhesh K. Shukla; Pranjali Vishwakarma; S.N. Upadhyay; Anil K Tripathi; H.C. Prasana; Suresh K. Dubey
Laboratory incubation experiments were carried out to assess the potential of methanotrophic culture for degrading TCE. Measurements of the growth rate and TCE degradation showed that the methanotrophs not only grew in presence of TCE but also degraded TCE. The rate of TCE degradation was found to be 0.19 ppm h-1. The reverse transcriptase-PCR test was conducted to quantify expression of pmoA and mmoX genes. RT-PCR revealed expression of pmoA gene only. This observation provides evidence that the pmoA gene was functionally active for pMMO enzyme during the study. The diversity of the methanotrophs involved in TCE degradation was assessed by PCR amplification, cloning, restriction fragment length polymorphism and phylogenetic analysis of pmoA genes. Results suggested the occurrence of nine different phylotypes belonging to Type II methanotrophs in the enriched cultures. Out of the nine, five clustered with, genera Methylocystis and rest got clustered in to a separate group. © 2008 Elsevier Ltd. All rights reserved.
Endophytic Bacteria in Plant Salt Stress Tolerance: Current and Future Prospects
(Springer New York LLC, 2019) Anukool Vaishnav; Awadhesh K. Shukla; Anjney Sharma; Roshan Kumar; Devendra K. Choudhary
Soil salinity is a major limiting factor for crop productivity worldwide and is continuously increasing owing to climate change. A wide range of studies and practices have been performed to induce salt tolerance mechanisms in plants, but their result in crop improvement has been limited due to lack of time and money. In the current scenario, there is increasing attention towards habitat-imposed plant stress tolerance driven by plant-associated microbes, either rhizospheric and/or endophytic. These microbes play a key role in protecting plants against various environmental stresses. Therefore, the use of plant growth-promoting microbes in agriculture is a low-cost and eco-friendly technology to enhance crop productivity in saline areas. In the present review, the authors describe the functionality of endophytic bacteria and their modes of action to enhance salinity tolerance in plants, with special reference to osmotic and ionic stress management. There is concrete evidence that endophytic bacteria serve host functions, such as improving osmolytes, anti-oxidant and phytohormonal signaling and enhancing plant nutrient uptake efficiency. More research on endophytes has enabled us to gain insights into the mechanism of colonization and their interactions with plants. With this information in mind, the authors tried to solve the following questions: (1) how do benign endophytes ameliorate salt stress in plants? (2) What type of physiological changes incur in plants under salt stress conditions? And (3), what type of determinants produced by endophytes will be helpful in plant growth promotion under salt stress? © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
Kinetics of bio-filtration of trichloroethylene by methanotrophs in presence of methanol
(2010) Awadhesh K. Shukla; R.S. Singh; S.N. Upadhyay; Suresh K. Dubey
The biodegradation of TCE was studied in a laboratory scale biofilter packed with wood charcoal and inoculated with mixed culture of methanotrophs isolated from local soil. The removal efficiency was found to be higher than 90% up to an inlet load of 5.1g/m3h. The maximum elimination capacity was 6.7g/m3h at an inlet loading rate of 11.3g/m3h. The reaction constants ECmax, Ks and Ki calculated from the experimental results are also presented. The biodegradation process is found to be inhibited at higher TCE concentration. The carbon dioxide production rate has been found to be a linear function of elimination capacity. The DNA finger printing techniques has indicated the presence of functionally active methanotrophic community including Methylocystis sp. in the biofilter. © 2010 Elsevier Ltd.
Substrate inhibition during bio-filtration of TCE using diazotrophic bacterial community
(2011) Awadhesh K. Shukla; R.S. Singh; S.N. Upadhyay; Suresh K. Dubey
The kinetics of biodegradation of TCE in the biofilter packed with wood charcoal and inoculated with diazotrophic bacterial community had been investigated. Use of Michaelis-Menten type model showed that substrate inhibition was present in the system. The kinetic model proposed by Edwards (1970) was used to calculate kinetic parameters-maximum elimination capacity (ECmax), substrate constant (Ks), and inhibition constant (KI). The model fitted well with the experimental data and the ECmax was found to be in the range of 10.8-6.1g/m3h. The Ks values depended upon substrate concentration and ranged from 0.024 to 0.043g/m3 indicating the high affinity of diazotrophs for TCE. The KI values were low and nearly constant (0.011-0.015g/m3) indicating a moderate substrate inhibition. © 2010 Elsevier Ltd.