Publications by authors named "Gunaseelan Dhanarajan"

4 Publications

  • Page 1 of 1

Production, partial purification and characterization of a proteoglycan bioemulsifier from an oleaginous yeast.

Bioprocess Biosyst Eng 2020 Oct 14;43(10):1747-1759. Epub 2020 May 14.

Department of Biotechnology, Indian Institute of Technology Kharagpur, West Bengal, Kharagpur, 721302, India.

In this study, Meyerozyma caribbica, an indigenously isolated oleaginous yeast, produced in media containing glucose a bioemulsifier that was partially characterized as a proteoglycan based on preliminary analysis. Optimization of carbon:nitrogen (C:N) ratio revealed 30:1 as the suitable ratio for enhanced production. Apart from higher emulsification activity (E: 70-80%), this molecule showed strong emulsion stability over a wide range of pH (2.0-9.0), salinity (0.05%-10%, w/v) and temperature (- 80 °C to + 50 °C). The current study emphasizes on the determination of critical media parameters for improved and stable bioemulsifier production coupled with partial characterization and identification of the molecule. Thus, a proteoglycan-based bioemulsifier with such a stable emulsifying property can serve as a versatile and potential component in food, cosmetics and pharmaceutical formulations.
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http://dx.doi.org/10.1007/s00449-020-02361-1DOI Listing
October 2020

Biosurfactant-biopolymer driven microbial enhanced oil recovery (MEOR) and its optimization by an ANN-GA hybrid technique.

J Biotechnol 2017 Aug 10;256:46-56. Epub 2017 May 10.

Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, 721302, India. Electronic address:

A lipopeptide biosurfactant produced by marine Bacillus megaterium and a biopolymer produced by thermophilic Bacillus licheniformis were tested for their application potential in the enhanced oil recovery. The crude biosurfactant obtained after acid precipitation effectively reduced the surface tension of deionized water from 70.5 to 28.25mN/m and the interfacial tension between lube oil and water from 18.6 to 1.5mN/m at a concentration of 250mgL. The biosurfactant exhibited a maximum emulsification activity (E) of 81.66% against lube oil. The lipopeptide micelles were stabilized by addition of Ca ions to the biosurfactant solution. The oil recovery efficiency of Ca conditioned lipopeptide solution from a sand-packed column was optimized by using artificial neural network (ANN) modelling coupled with genetic algorithm (GA) optimization. Three important parameters namely lipopeptide concentration, Ca concentration and solution pH were considered for optimization studies. In order to further improve the recovery efficiency, a water soluble biopolymer produced by Bacillus licheniformis was used as a flooding agent after biosurfactant incubation. Upon ANN-GA optimization, 45% tertiary oil recovery was achieved, when biopolymer at a concentration of 3gL was used as a flooding agent. Oil recovery was only 29% at optimal conditions predicted by ANN-GA, when only water was used as flooding solution. The important characteristics of biopolymers such as its viscosity, pore plugging capabilities and bio-cementing ability have also been tested. Thus, as a result of biosurfactant incubation and biopolymer flooding under the optimal process conditions, a maximum oil recovery of 45% was achieved. Therefore, this study is novel, timely and interesting for it showed the combined influence of biosurfactant and biopolymer on solubilisation and mobilization of oil from the soil.
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http://dx.doi.org/10.1016/j.jbiotec.2017.05.007DOI Listing
August 2017

An Antimicrobial Metabolite from Bacillus sp.: Significant Activity Against Pathogenic Bacteria Including Multidrug-Resistant Clinical Strains.

Front Microbiol 2015 15;6:1335. Epub 2015 Dec 15.

Department of Biological Sciences, BITS Pilani- K. K. Birla Goa Campus Goa, India.

In this study, the cell free modified tryptone soya broth (pH 7.4 ± 0.2) of Bacillus subtilis URID 12.1 showed significant antimicrobial activity against multidrug-resistant strains of Staphylococcus aureus, S. epidermidis, Streptococcus pyogenes and Enterococcus faecalis. The partially purified antimicrobial molecule was found to be resistant to extremes of pH and temperatures and also to higher concentrations of trypsin and proteinase K. The antimicrobial molecule was purified by a three-step method that included reversed-phase high performance liquid chromatography (RP-HPLC). The minimum inhibitory concentration (MIC) values were determined for 14 species of bacteria using a microbroth dilution technique. The HPLC-purified fraction showed the MICs ranging from 0.5 to 16 μg/ml for methicillin and vancomycin-resistant Staphylococcus aureus (MVRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) strains. The molecular mass of the antimicrobial compound was determined to be 842.37 Da. The same antimicrobial fraction showed negligible haemolytic activity against human red blood cells even at a concentration as high as 100 μg/ml. Because of its significant antimicrobial activity at low MIC values coupled with its non-haemolytic property, it may prove to be a novel antimicrobial lead molecule.
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http://dx.doi.org/10.3389/fmicb.2015.01335DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4678185PMC
December 2015

Marine lipopeptide Iturin A inhibits Akt mediated GSK3β and FoxO3a signaling and triggers apoptosis in breast cancer.

Sci Rep 2015 May 14;5:10316. Epub 2015 May 14.

School of Medical Science and Technology, Indian Institute of Technology Kharagpur, Kharagpur-721302, West Bengal, India.

Akt kinase is a critical component of the PI3K/Akt signaling pathway, which is frequently over expressed in human cancers including breast. Therapeutic regimens for inhibiting breast cancer with aberrant Akt activity are essential. Here, we evaluated antitumor effect of a marine bacteria derived lipopeptide 'Iturin A' on human breast cancer in vitro and in vivo through disrupting Akt pathway. Proliferation of MDA-MB-231 and MCF-7 breast cancer cells were significantly inhibited by Iturin A and it induced apoptosis as confirmed by increased Sub G1 populations, DNA fragmentation, morphological changes and western blot analysis. Furthermore, Iturin A inhibited EGF induced Akt phosphorylation (Ser473 and Thr308) and its downstream targets GSK3β and FoxO3a. Iturin A inactivated MAPK as well as Akt kinase leading to the translocation of FoxO3a to the nucleus. Gene silencing of Akt in MDA-MB-231 and MCF-7 cells reduced the sensitivity of cancer cells to Iturin A. Interestingly, overexpression of Akt with Akt plasmid in cancer cells caused highly susceptible to induce apoptosis by Iturin A treatment. In a xenograft model, Iturin A inhibited tumor growth with reduced expressions of Ki-67, CD-31, P-Akt, P-GSK3β, P-FoxO3a and P-MAPK. Collectively, these findings imply that Iturin A has potential anticancer effect on breast cancer.
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http://dx.doi.org/10.1038/srep10316DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4431395PMC
May 2015
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