Ameeta Ravi Kumar

Environmental and industrial applications of Yarrowia lipolytica

Yarrowia lipolytica is a fungus that degrades hydrophobic substrates very efficiently. The fungus displays several important characteristics that have encouraged researchers to study various basic biological and biotechnological applications in detail. Although the organism has been used as model system for studying dimorphism, salt tolerance, heterologous protein expression, and lipid accumulation, there are no recent reviews on the environmental and industrial applications of this organism. Included here are applications in bioremediation of environments contaminated with aliphatic and aromatic compounds, organic pollutants, 2,4,6-trinitrotoluene, and metals. A variety of industrially important recent processes for the synthesis of β-hydroxy butyrate, l-dopa, and emulsifiers have also been reviewed. Production of unique inherent enzymes (inulinases, α-mannosidases), novel applications of esterases and lipases, and the use of the fungus for heterologous expression of biotechnologically relevant products have also been highlighted. The review while entailing a general overview focuses critically on some of the recent advances on the applications of this yeast. The examples cited here demonstrate the use of wild-type, mutant as well as genetically manipulated strains of Y. lipolytica for the development of different products, processes, and technologies. This also throws light on how a single organism can be versatile with respect to its metabolic abilities and how it can be exploited for a variety of purposes. This review will thus form a base for future developments in this field.

Potent α-amylase inhibitory activity of Indian Ayurvedic medicinal plants

BackgroundIndian medicinal plants used in the Ayurvedic traditional system to treat diabetes are a valuable source of novel anti-diabetic agents. Pancreatic α-amylase inhibitors offer an effective strategy to lower the levels of post-prandial hyperglycemia via control of starch breakdown. In this study, seventeen Indian medicinal plants with known hypoglycemic properties were subjected to sequential solvent extraction and tested for α-amylase inhibition, in order to assess and evaluate their inhibitory potential on PPA (porcine pancreatic α-amylase). Preliminary phytochemical analysis of the lead extracts was performed in order to determine the probable constituents.MethodsAnalysis of the 126 extracts, obtained from 17 plants (Aloe vera (L.) Burm.f., Adansonia digitata L., Allium sativum L., Casia fistula L., Catharanthus roseus (L.) G. Don., Cinnamomum verum Persl., Coccinia grandis (L.) Voigt., Linum usitatisumum L., Mangifera indica L., Morus alba L., Nerium oleander L., Ocimum tenuiflorum L., Piper nigrum L., Terminalia chebula Retz., Tinospora cordifolia (Willd.) Miers., Trigonella foenum-graceum L., Zingiber officinale Rosc.) for PPA inhibition was initially performed qualitatively by starch-iodine colour assay. The lead extracts were further quantified with respect to PPA inhibition using the chromogenic DNSA (3, 5-dinitrosalicylic acid) method. Phytochemical constituents of the extracts exhibiting≥ 50% inhibition were analysed qualitatively as well as by GC-MS (Gas chromatography-Mass spectrometry).ResultsOf the 126 extracts obtained from 17 plants, 17 extracts exhibited PPA inhibitory potential to varying degrees (10%-60.5%) while 4 extracts showed low inhibition (< 10%). However, strong porcine pancreatic amylase inhibitory activity (> 50%) was obtained with 3 isopropanol extracts. All these 3 extracts exhibited concentration dependent inhibition with IC50 values, viz., seeds of Linum usitatisumum (540 μgml-1), leaves of Morus alba (1440 μgml-1) and Ocimum tenuiflorum (8.9 μgml-1). Acarbose as the standard inhibitor exhibited an IC50 (half maximal inhibitory concentration)value of 10.2 μgml-1. Phytochemical analysis revealed the presence of alkaloids, tannins, cardiac glycosides, flavonoids, saponins and steroids with the major phytoconstituents being identified by GC-MS.ConclusionsThis study endorses the use of these plants for further studies to determine their potential for type 2 diabetes management. Results suggests that extracts of Linum usitatisumum, Morus alba and Ocimum tenuiflorum act effectively as PPA inhibitors leading to a reduction in starch hydrolysis and hence eventually to lowered glucose levels.

Influence of biomass and gold salt concentration on nanoparticle synthesis by the tropical marine yeast Yarrowia lipolytica NCIM 3589

Cell-associated gold nanoparticles and nanoplates were produced when varying number of Yarrowia lipolytica cells were incubated with different concentrations of chloroauric acid (HAuCl(4)) at pH 4.5. With 10(9)cells ml(-1) and 0.5 or 1.0 mM of the gold salt, the reaction mixtures developed a purple or golden red colour, respectively, and gold nanoparticles were synthesized. Nanoparticles of varying sizes were produced when 10(10)cells ml(-1) were incubated with 0.5, 1.0 or 2.0 mM chloroauric acid salt. With 3.0, 4.0 or 5.0 mM HAuCl(4), nanoplates were also observed. With 10(11)cells ml(-1) nanoparticles were synthesized with almost all the gold salt concentrations. The cell-associated particles were released outside when nanoparticle-loaded cells were incubated at low temperature (20 degrees C) for 48 h. With increasing salt concentrations and a fixed number of cells, the size of the nanoparticles progressively increased. On the other hand, with increasing cell numbers and a constant gold salt concentration, the size of nanoparticles decreased. These results indicate that by varying the number of cells and the gold salt concentration, a variety of nanoparticles and nanoplates can be synthesized. Fourier transform infrared (FTIR) spectroscopy revealed the possible involvement of carboxyl, hydroxyl and amide groups on the cell surfaces in nanoparticle synthesis.

Evaluation of Traditional Indian Antidiabetic Medicinal Plants for Human Pancreatic Amylase Inhibitory Effect In Vitro

Pancreatic α-amylase inhibitors offer an effective strategy to lower the levels of post prandial hyperglycemia via control of starch breakdown. Eleven Ayurvedic Indian medicinal plants with known hypoglycemic properties were subjected to sequential solvent extraction and tested for α-amylase inhibition, in order to assess and evaluate their inhibitory potential on pancreatic α-amylase. Analysis of 91 extracts, showed that 10 exhibited strong Human Pancreatic Amylase (HPA) inhibitory potential. Of these, 6 extracts showed concentration dependent inhibition with IC50 values, namely, cold and hot water extracts from Ficus bengalensis bark (4.4 and 125 μgmL−1), Syzygium cumini seeds (42.1 and 4.1 μgmL−1), isopropanol extracts of Cinnamomum verum leaves (1.0 μgmL−1) and Curcuma longa rhizome (0.16 μgmL−1). The other 4 extracts exhibited concentration independent inhibition, namely, methanol extract of Bixa orellana leaves (49 μgmL−1), isopropanol extract from Murraya koenigii leaves (127 μgmL−1), acetone extracts from C. longa rhizome (7.4 μgmL−1) and Tribulus terrestris seeds (511 μgmL−1). Thus, the probable mechanism of action of the above fractions is due to their inhibitory action on HPA, thereby reducing the rate of starch hydrolysis leading to lowered glucose levels. Phytochemical analysis revealed the presence of alkaloids, proteins, tannins, cardiac glycosides, flavonoids, saponins and steroids as probable inhibitory compounds.

Antidiabetic Indian Plants: A Good Source of Potent Amylase Inhibitors

Diabetes is known as a multifactorial disease. The treatment of diabetes (Type II) is complicated due to the inherent patho-physiological factors related to this disease. One of the complications of diabetes is post-prandial hyperglycemia (PPHG). Glucosidase inhibitors, particularly α-amylase inhibitors are a class of compounds that helps in managing PPHG. Six ethno-botanically known plants having antidiabetic property namely, Azadirachta indica Adr. Juss.; Murraya koenigii (L.) Sprengel; Ocimum tenuflorum (L.) (syn: Sanctum); Syzygium cumini (L.) Skeels (syn: Eugenia jambolana); Linum usitatissimum (L.) and Bougainvillea spectabilis were tested for their ability to inhibit glucosidase activity. The chloroform, methanol and aqueous extracts were prepared sequentially from either leaves or seeds of these plants. It was observed that the chloroform extract of O. tenuflorum; B. spectabilis; M. koenigii and S. cumini have significant α-amylase inhibitory property. Plants extracts were further tested against murine pancreatic, liver and small intestinal crude enzyme preparations for glucosidase inhibitory activity. The three extracts of O. tenuflorum and chloroform extract of M. koenigi showed good inhibition of murine pancreatic and intestinal glucosidases as compared with acarbose, a known glucosidase inhibitor.

Removal of chromium (VI) ions from aqueous solution by adsorption onto two marine isolates of Yarrowia lipolytica.

The removal of chromium (VI) ions from aqueous solutions by the biomass of two marine strains of Yarrowia lipolytica (NCIM 3589 and 3590) was studied with respect to pH, temperature, biomass, sea salt concentration, agitation speed, contact time and initial concentration of chromium (VI) ions. Maximum biosorption was observed at pH 1.0 and at a temperature of 35 degrees C. Increase in biomass and sea salts resulted in a decreased metal uptake. With an agitation speed of 130 rpm, equilibrium was attained within 2h. Under optimum conditions, biosorption was enhanced with increasing concentrations of Cr (VI) ions. NCIM 3589 and 3590 displayed a specific uptake of Cr (VI) ions of 63.73+/-1.3 mg g(-1) at a concentration of 950 ppm and 46.09+/-0.23 mg g(-1) at 955 ppm, respectively. Scatchard plot analysis revealed a straight line allowing the data to be fitted in the Langmuir model. The adsorption data obtained also fitted well to the Freundlich isotherm. The surface sequestration of Cr (VI) by Y. lipolytica was investigated with a scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS) as well as with ED-X-ray fluorescence (ED-XRF). Fourier transform infrared (FTIR) spectroscopy revealed the involvement of carboxyl, hydroxyl and amide groups on the cell surfaces in chromium binding.

Anti-biofilm potential of a glycolipid surfactant produced by a tropical marine strain of Serratia marcescens.

A tropical marine bacterium isolated from the hard coral, Symphyllia sp. was identified as Serratia marcescens on the basis of morphological, biochemical and 16S rDNA analysis. The bacterium showed antimicrobial activity towards the pathogens Candida albicans and Pseudomonas aeruginosa and the marine biofouling bacterium Bacillus pumilus. S. marcescens displayed biosurfactant activity as evidenced by drop collapse, blood hemolysis and surface tension reduction (52.0–27 mN m−1). The active compound was purified by solvent extraction and silicic acid chromatography. Characterization was by thin layer chromatography, gas chromatography mass spectroscopy (GC-MS), Fourier transform infrared (FTIR) spectroscopy and 1H as well as 13C nuclear magnetic resonance (NMR) analysis. The surfactant was found to be a glycolipid composed of glucose and palmitic acid. The glycolipid prevented adhesion of C. albicans BH, P. aeruginosa PAO1 and B. pumilus TiO1. The glycolipid also disrupted preformed biofilms of these cultures in microtitre plates. Confocal laser scanning microscopy and electron microscopy confirmed the effective removal of biofilms from glass surfaces. The glycolipid derived from S. marcescens could thus serve as a potential anti-biofilm agent.

Disruption of fungal and bacterial biofilms by lauroyl glucose

Aim:  The ability of enzymatically synthesized lauroyl glucose to disrupt fungal (Candida albicans, Candida lipolytica) and bacterial (Pseudomonas aeruginosa PAO1, Pseudomonas aureofaciens) biofilms was investigated.

Yarrowia lipolytica and pollutants: Interactions and applications

Yarrowia lipolytica is a dimorphic, non-pathogenic, ascomycetous yeast species with distinctive physiological features and biochemical characteristics that are significant in environment-related matters. Strains naturally present in soils, sea water, sediments and waste waters have inherent abilities to degrade hydrocarbons such as alkanes (short and medium chain) and aromatic compounds (biphenyl and dibenzofuran). With the application of slow release fertilizers, design of immobilization techniques and development of microbial consortia, scale-up studies and in situ applications have been possible. In general, hydrocarbon uptake in this yeast is mediated by attachment to large droplets (via hydrophobic cell surfaces) or is aided by surfactants and emulsifiers. Subsequently, the internalized hydrocarbons are degraded by relevant enzymes innately present in the yeast. Some wild-type or recombinant strains also detoxify nitroaromatic (2,4,6-trinitrotoluene), halogenated (chlorinated and brominated hydrocarbons) and organophosphate (methyl parathion) compounds. The yeast can tolerate some metals and detoxify them via different biomolecules. The biomass (unmodified, in combination with sludge, magnetically-modified and in the biofilm form) has been employed in the biosorption of hexavalent chromium ions from aqueous solutions. Yeast cells have also been applied in protocols related to nanoparticle synthesis. The treatment of oily and solid wastes with this yeast reduces chemical oxygen demand or value-added products (single cell oil, single cell protein, surfactants, organic acids and polyalcohols) are obtained. On account of all these features, the microorganism has established a place for itself and is of considerable value in environment-related applications.

Removal of hexavalent chromium ions by Yarrowia lipolytica cells modified with phyto-inspired Fe0/Fe3O4 nanoparticles

The removal of hexavalent chromium [Cr (VI)], an important ground water pollutant by phyto-inspired Fe(0)/Fe(3)O(4) nanocomposite-modified cells of Yarrowia lipolytica (NCIM 3589 and NCIM 3590), was investigated. Electron microscopy and magnetometer studies indicated an effective modification of yeast cell surfaces by the nanocomposites. The effect of pH, temperature, agitation speed, contact time and initial metal ion concentration on the removal of Cr (VI) was determined. The specific uptake values at pH 2.0 were 186.32±3.17 and 137.31±4.53 mg g(-1) for NCIM 3589 and NCIM 3590, respectively, when 1000 mg L(-1) of metal ion concentrations were used. The equilibrium data fitted to Scatchard, Langmuir and linearized Freundlich models suggesting that adsorption played a role in the removal of Cr (VI) ions. The surface modified yeast cells displayed higher values of Langmuir and Scatchard coefficients than the unmodified cells indicating that the former were more efficient in Cr (VI) removal. The enhanced detoxification of Cr (VI) ions by this composite material could be attributed to the reductive power of the Fe(0)/Fe(3)O(4) nanocomposites as well the yeast cell surface functional groups.