Polylactic acid: synthesis and biomedical applications.

Social and economic development has driven considerable scientific and engineering efforts on the discovery, development and utilization of polymers. Polylactic acid (PLA) is one of the most promising biopolymers as it can be produced from nontoxic renewable feedstock. PLA has emerged as an important polymeric material for biomedical applications on account of its properties such as biocompatibility, biodegradability, mechanical strength and process ability. Lactic acid (LA) can be obtained by fermentation of sugars derived from renewable resources such as corn and sugarcane. PLA is thus an eco-friendly nontoxic polymer with features that permit use in the human body. Although PLA has a wide spectrum of applications, there are certain limitations such as slow degradation rate, hydrophobicity and low impact toughness associated with its use. Blending PLA with other polymers offers convenient options to improve associated properties or to generate novel PLA polymers/blends for target applications. A variety of PLA blends have been explored for various biomedical applications such as drug delivery, implants, sutures and tissue engineering. PLA and their copolymers are becoming widely used in tissue engineering for function restoration of impaired tissues due to their excellent biocompatibility and mechanical properties. The relationship between PLA material properties, manufacturing processes and development of products with desirable characteristics is described in this article. LA production, PLA synthesis and their applications in the biomedical field are also discussed.

Nocardiopsis species: a potential source of bioactive compounds.

Members of the genus Nocardiopsis are an ecologically versatile and biotechnologically important group of Actinomycetes. Most of the isolates are halotolerant or halophilic and they prevail in soils, marine environments or hypersaline locations. To aid their survival under these conditions, they mainly produce extremozymes, compatible solutes, surfactants and bioactive compounds. The current review details the bioactive compounds obtained for this genus. Important antimicrobial agents obtained from this genus include polyketides, phenzines, quinoline alkaloids, terphenyls, proteins, thiopeptides and amines. Polyketides and peptides displaying potent anticancer activities are also significant. Tumour promoting agents, P-glycoprotein (P-gp) inhibitors, immunomodulators and protein kinase inhibitors are other relevant products obtained from Nocardiopsis species. Structurally, polyketides (synthesized by polyketide synthases) and peptides (made by nonribosomal peptide synthetases or cyclodipeptide synthases) are important compounds. Considered here are also toxins, anti photoaging and adipogenic agents produced by this genus. The gene clusters mediating the synthesis of bioactive compounds have been described. Commercially available products (Apoptolidins and K-252a) derived from this genus have also been described. This review highlights the significance of a single genus in producing an assortment of compounds with varied biological activities. On account of these features, the members of this genus have established a place for themselves and are of considerable value in producing compounds with profound bio-medical applications.

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.

Biofilm formation by a biotechnologically important tropical marine yeast isolate, Yarrowia lipolytica NCIM 3589.

Biofilm formation by Yarrowia lipolytica, a biotechnologically important fungus in microtitre plates, on glass slide surfaces and in flow cell was investigated. In microtitre plates, there was a short lag phase of adhesion followed by a period of rapid biofilm growth. The fungus formed extensive biofilms on glass slides, whereas in flow-cells a multicellular, three-dimensional microcolony structure was observed. The isolate formed biofilms in seawater and in fresh water media at neutral pH when grown in microtitre plates. The carbon sources differentially affected formation of biofilms in microtitre plates. Lactic acid, erythritol, glycerol, glucose and edible oils supported the formation of biofilms, while alkanes resulted in sub-optimal biofilm development. A variation in the morphology of the fungus was observed with different carbon sources. The results point to the possible existence of highly structured biofilms in varied ecological niches from where the yeast is isolated.

Biofilm formation by a biotechnologically important tropical marine yeast isolate, Yarrowia lipolytica NCIM 3589.

Biofilm formation by Yarrowia lipolytica, a biotechnologically important fungus in microtitre plates, on glass slide surfaces and in flow cell was investigated. In microtitre plates, there was a short lag phase of adhesion followed by a period of rapid biofilm growth. The fungus formed extensive biofilms on glass slides, whereas in flow-cells a multicellular, three-dimensional microcolony structure was observed. The isolate formed biofilms in seawater and in fresh water media at neutral pH when grown in microtitre plates. The carbon sources differentially affected formation of biofilms in microtitre plates. Lactic acid, erythritol, glycerol, glucose and edible oils supported the formation of biofilms, while alkanes resulted in sub-optimal biofilm development. A variation in the morphology of the fungus was observed with different carbon sources. The results point to the possible existence of highly structured biofilms in varied ecological niches from where the yeast is isolated.

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. METHODS AND RESULTS: Preformed biofilms of C. albicans and C. lipolytica in polystyrene microtitre plates were disrupted upto 45% and 65%, respectively, while P. aeruginosa and P. aureofaciens biofilms were disrupted by 51% and 57%. Precoating of the microtitre wells with lauroyl glucose affected cell attachment and biofilm growth of all the cultures to a lesser extent. With C. albicans and C. lipolytica, there was 11% and 32% decrease in the development of biofilms, respectively. With P. aeruginosa and P. aureofaciens, the reduction was 21% and 12% after 48 h. Lauroyl glucose effectively inhibited the formation of biofilms on glass slide surfaces when added along with the inoculum. Analysis by confocal laser scanning microscopy showed that the growth of the biofilms was lesser as compared with the control experiments. Lauroyl glucose displayed minimum inhibitory concentration values >500 microg ml(-1) for the test cultures and was comparable to that obtained with acetyl salicylate. CONCLUSION: Lauroyl glucose reduces biofilm growth of all the four test cultures on polystyrene and glass surfaces. SIGNIFICANCE AND IMPACT OF THE STUDY: This report is a novel application of the enzymatically synthesized, environmental-friendly nonionic surfactant.

2,4,6-trinitrotoluene transformation by a tropical marine yeast, Yarrowia lipolytica NCIM 3589.

Yarrowia lipolytica NCIM 3589, a tropical marine degrader of hydrocarbons and triglycerides transformed 2,4,6-trinitrotoluene (TNT) very efficiently. Though this yeast could not utilize TNT as the sole carbon or nitrogen source, it was capable of reducing the nitro groups in TNT to aminodinitrotoluene (ADNT). In a complete medium containing glucose and ammonium sulphate as the available carbon and nitrogen sources respectively, the culture was able to completely transform 1 mM (227 ppm) of TNT under such conditions. A dual pathway was found to be functional, one of which resulted in the formation of the hydride-Meisenheimer complex (H(-)TNT) as a transiently accumulating metabolite that was subsequently denitrated to 2,4-dinitrotoluene (2,4-DNT), whereas the other pathway resulted in the formation of amino derivatives. The presence of increasing amounts of reducing equivalents in the form of glucose promoted better growth and the nitroreductases of this yeast to reduce the aromatic ring to 2,4-DNT although, the reduction of the nitro groups to amino groups was the major functional pathway. The ability of this tropical marine yeast to transform TNT into products such as 2,4-DNT which in turn could be metabolized by other microbes has implications in the use of this yeast for bioremediation of TNT polluted marine environments.

Palm oil mill effluent treatment by a tropical marine yeast.

Palm oil mill effluent (POME), from a factory site in India contained about 250,000 mg l(-1) chemical oxygen demand (COD), 11,000 mg l(-1) biochemical oxygen demand, 65 mg l(-1) total dissolved solids and 9000 mg l(-1) of chloroform-soluble material. Treatment of this effluent using Yarrowia lipolytica NCIM 3589, a marine hydrocarbon-degrading yeast isolated from Mumbai, India, gave a COD reduction of about 95% with a retention time of two days. Treatment with a chemical coagulant further reduced the COD and a consortium developed from garden soil clarified the effluent and adjusted the pH to between 6 and 7. The complete treatment reduced the COD content to 1500 mg l(-1) which is a 99% reduction from the original.

Hydrocarbon degraders from tropical marine environments.

Analysis of 20 samples of marine mud and water around Mumbai resulted in the isolation of 17 bacteria and yeasts all of which were able to degrade more than 10% of the supplied crude oil. The yeasts strains were important degraders of the aliphatic fraction of crude. All the isolated yeasts belonged to the genus Candida. Using biochemical tests these were identified as Candida parapsilosis, C. albicans, C. guilliermondii, Yarrowia lipolytica, C. tropicalis and C. intermedia. Y. lipolytica was the best degrader utilizing 78% of the aliphatic fraction of Bombay High crude oil. None of these isolates degraded the aromatic or ashphaltene fractions. All the isolates required aeration, nitrogen and phosphate supplementation for optimal degradation. Four out of the six yeasts are human pathogens.