Gunaseelan Dhanarajan

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

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.

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

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-1. The biosurfactant exhibited a maximum emulsification activity (E24) of 81.66% against lube oil. The lipopeptide micelles were stabilized by addition of Ca2+ ions to the biosurfactant solution. The oil recovery efficiency of Ca2+ 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, Ca2+ 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-1 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.

Integrated in situ transesterification for improved biodiesel production from oleaginous yeast: a value proposition for possible industrial implication

The conventional biodiesel production process using oleaginous yeast biomass often involves multiple energy intensive unit operations and processing steps that increase the overall cost and reduce the economic viability of the biodiesel product. Thus, this study attempts to design and optimize an in situ process for the direct conversion of lipids in disrupted wet biomass of oleaginous Pichia guilliermondii with an average total lipid content of 50 ± 2% [w/w, on dry cell weight (DCW) basis] to biodiesel, while bypassing important steps of biomass processing such as drying and lipid extraction. The in situ process involved applying sonication as an energy efficient cell disruption strategy that helped extract 44.5 ± 2.3% (w/w) neutral lipid on a dry cell weight (DCW) basis, using methanol-hexane as the most appropriate binary solvent system. Subsequently, the critical transesterification parameters such as biomass : methanol (w/v), catalyst concentration (v/v, %), reaction time and temperature that influence in situ biodiesel production were standardized. A maximum FAME (fatty acid methyl esters) yield of 92% (w/w of lipid), was achieved. This yield is comparable to that obtained by the ex-situ multistep transesterification process that requires approximately 7 h more than the in situ process, thereby resulting in greater productivity. The properties of the biodiesel product, as calculated from the FAME profile using empirical equations, conformed to the ASTM and CEN standards for it to qualify as an alternative to petro-diesel. Reports on direct transesterification of yeast biomass are scant. Thus, to the best of our knowledge, the developed in situ process integrating cell disruption, lipid extraction and transesterification is more energy efficient and productive as compared to those reported on yeast or algal feedstocks.

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

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.

Performance evaluation of a yeast biorefinery as a sustainable model for co-production of biomass, bioemulsifier, lipid, biodiesel and animal-feed components using inexpensive raw materials

Oleaginous yeasts have gained increasing attention as feedstock for biodiesel and other value-added products due to their high growth rates coupled with lipid accumulation abilities. However, the development of a technologically and economically sustainable biodiesel manufacturing process from yeasts necessitates the use of low-cost substrates and co-production of value-added by-products in a biorefinery model. Thus, the present study endeavors to concomitantly produce lipid and bioemulsifier from the isolated oleaginous yeast Pichia guilliermondii using inexpensive raw materials. Various low-cost raw materials, such as molasses, crude glycerol, distillery wastewater (DWW) and corn steep liquor (CSL), are tested to develop a judicious combination of substrates for the optimal production of yeast biomass and lipid for biodiesel application. Among the various combinations tested, crude glycerol when supplemented with CSL and mineral salts results in a maximum biomass concentration of 24.47 ± 0.78 g L−1 with 52.09 ± 2.03% lipid on a dry weight basis. Gas chromatographic analysis of the transesterified yeast lipid reveals that the compositions of fatty acid methyl esters vary with the substrates used for lipid production. However, the biodiesel properties are found to comply with the international standards, ASTM D6751 and EN14214. Studies on the emulsification activity reveal the extracellular production of bioemulsifer by the oleaginous yeast. Further biochemical analysis of the lipid-extracted biomass shows that it contains up to 24.6% ± 0.83% protein and 44.2% ± 1.41% carbohydrate, which indicate its potential use as animal feed. A preliminary cost estimate of lipid production shows the economic advantages of cheaper raw materials over synthetic media. Thus, as a proof of a novel biorefinery concept, an efficient and sustainable yeast biorefinery is successfully developed for the concomitant production of biodiesel, bioemulsifier and animal feed-components with simultaneous valorization of waste as low-cost substrates.