Synthesis of sugar esters in solvent mixtures by lipases from Thermomyces lanuginosus and Candida antarctica B, and their antimicrobial properties

Biodegradable polycaprolactone-titania nanocomposites: preparation, characterization and antimicrobial properties

Nanocomposites obtained from the incorporation of synthesized TiO₂ nanoparticles (≈10 nm average primary particle size) in different amounts, ranging from 0.5 to 5 wt.%, into a biodegradable polycaprolactone matrix are achieved via a straightforward and commercial melting processing. The resulting nanocomposites have been structurally and thermally characterized by transmission electron microscopy (TEM), wide/small angle X-ray diffraction (WAXS/SAXS, respectively) and differential scanning calorimetry (DSC). TEM evaluation provides evidence of an excellent nanometric dispersion of the oxide component in the polymeric matrix, with aggregates having an average size well below 100 nm. Presence of these TiO₂ nanoparticles induces a nucleant effect during polymer crystallization. Moreover, the antimicrobial activity of nanocomposites has been tested using both UV and visible light against Gram-negative Escherichia coli bacteria and Gram-positive Staphylococcus aureus. The bactericidal behavior has been explained through the analysis of the material optical properties, with a key role played by the creation of new electronic states within the polymer-based nanocomposites.

Antimicrobial Ionic Liquids with Fumarate Anion

The shortage of new antimicrobial drugs and increasing resistance of microbe to antimicrobial agents have been of some concern. The formulation studies of new antibacterial and antifungal agents have been an active research field. Ionic liquids are known as designed liquids with controllable physical/chemical/biological properties and specific functions, which have been attracting considerable interest over recent years. However, no attention has been made towards the preparation of ionic liquids with antimicrobial activities. In this paper, a new class of ionic liquids (ILs) with fumarate anion was synthesized by neutralization of aqueous 1-butyl-3-methylimidazolium hydroxide with equimolar monoester fumarate and characterized using NMR and thermal gravimetric analysis. The ILs are soluble in water and polar organic solvents and also soluble in the common ILs. The antimicrobial activities of the ILs are more active than commercially available potassium sorbate and are greatly affected by the alkyl chain length. The significant antimicrobial properties observed in this research suggest that the ILs may have potential applications in the modern biotechnology.

Synthesis, characterization, antibacterial and antifungal evaluation of novel monosaccharide esters

A novel series of 3-(2-furyl)acrylate monosaccharide esters Ia–f and menthyloxycarbonyl monosaccharide esters IIa–f were designed and synthesized. The chemical structures of the target compounds were confirmed by IR, ¹H- and ¹³C-NMR and ESI-MS, and the target compounds were investigated for their in vitro antibacterial and antifungal activities. The antibacterial screening results showed that the 3-(2-furyl)acrylate monosaccharide ester derivatives Ia–f were either inactive or only weakly active against the three Gram-positive bacterial strains tested, whereas the menthyloxycarbonyl monosaccharide ester derivatives IIa–f exhibited higher levels of activity, with compound IIe being especially potent. The results of the antifungal screening revealed that compounds Ib, Ie, IIb and IIc displayed potent in vitro activities, whereas If and IIf showed promising activities against all of the microorganisms tested, with If exhibiting levels of activity deserving of further investigation.

Effect of lactose monolaurate on pathogenic and nonpathogenic bacteria

The antimicrobial activities of sucrose monolaurate and a novel ester, lactose monolaurate (LML), were tested. Gram-positive bacteria were more susceptible than Gram-negative bacteria to both esters. The minimal bactericidal concentrations of LML were 5 to 9.5 mM for Listeria monocytogenes isolates and 0.2 to 2 mM for Mycobacterium isolates.

Environmentally friendly approaches to the synthesis of new antibiotics from sugars

In light of the biological importance of carbohydrates and their role when present in antibiotic agents, the design and synthesis of carbohydrate-based antibiotics has occupied a prominent place in drug discovery. This review focuses on synthetic carbohydrate antimicrobial agents, giving special emphasis to novel structures easily accessible from readily available carbohydrate precursors.

Lipophilized epigallocatechin gallate (EGCG) derivatives as novel antioxidants

Epigallocatechin gallate (EGCG) is the major polyphenol in green tea and known to render many health benefits associated with tea consumption. EGCG was modified structurally to improve its lipophilicity, expand its application in lipophilic media, and enhance its cellular absorption in vivo. Esterification of the water-soluble EGCG with selected long-chain saturated and unsaturated fatty acids was carried out, followed by a purification process. Ester derivatives of EGCG with stearic acid (SA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) were prepared, and their enhanced lipophilicity was confirmed by octanol-water partition coefficient. The chemical structures of the EGCG derivatives, determined by HPLC-MS and ¹H and ¹³C NMR, were EGCG-3',5',3'',5''-O-tetraesters of SA, EPA, and DHA. The lipophilized EGCG derivatives exhibited greater antioxidant activity in scavenging the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical than EGCG itself. The results suggest that EGCG derivatives may be used as potential lipophilic antioxidants in the food, cosmetic, and medicinal industries.

Molten globule-triggered inactivation of a thermostable and solvent stable lipase in hydrophilic solvents

The use of lipase in hydrophilic solvent is usually hampered by inactivation. The solvent stability of a recombinant solvent stable lipase isolated from thermostable Bacillus sp. strain 42 (Lip 42), in DMSO and methanol were studied at different solvent-water compositions. The enzymatic activities were retained in up to 45% v/v solvent compositions. The near-UV CD spectra indicated that tertiary structures were perturbed at 60% v/v and above. Far-UV CD in methanol indicated the secondary structure in Lip 42 was retained throughout all solvent compositions. Fluorescence studies indicated formations of molten globules in solvent compositions of 60% v/v and above. The enzyme was able to retain its secondary structures in the presence of methanol; however, there was a general reduction in beta-sheet and an increase in alpha-helix contents. The H-bonding arrangements triggered in methanol and DMSO, respectively, caused different forms of tertiary structure perturbations on Lip 42, despite both showing partial denaturation with molten globule formations.

In vitro antimicrobial activity and mechanism of action of novel carbohydrate fatty acid derivatives against Staphylococcus aureus and MRSA

AIMS

This study investigates the antimicrobial activity and mode of action of novel carbohydrate fatty acid (CFA) derivatives against Staphylococcus aureus and methicillin-resistant Staph. aureus (MRSA).

METHODS AND RESULTS

Minimum inhibitory concentrations (MICs) and the effect of CFA derivatives on lag phase were determined using a broth microdilution method. Lauric acid carbohydrate esters and corresponding ether analogues showed the greatest antimicrobial activity with MIC values between 0.04 and 0.16 mmol l(-1). Leakage studies at 260 nm following exposure to CFA derivatives at 4x MIC showed a significant increase in membrane permeability for all compounds, after c. 15 min exposure except for the lauric beta ether CFA derivative. Further assessment using both BacLight and luminescence ATP assays confirmed that an increase in membrane permeability and reduced metabolic activity was associated with CFA treatment.

CONCLUSIONS

All strains were significantly inhibited by the novel compounds studied, and efficacy was related to specific structural features. Cell-membrane permeabilization was associated with CFA treatment and may account for at least a component of the mode of action of these compounds.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study reports the antimicrobial action of CFA compounds against a range of Staph. aureus and MRSA strains, and provides insights into their mode of action.

Production, partial purification and characterization of organic solvent tolerant lipase from Burkholderia multivorans V2 and its application for ester synthesis

Burkholderia multivorans V2 (BMV2) isolated from soil was found to produce an extracellular solvent tolerant lipase (6.477 U/mL). This lipase exhibited maximum stability in n-hexane retaining about 97.8% activity for 24h. After performing statistical optimization of medium components for lipase production, a 2.2-fold (14 U/mL) enhancement in the lipase production was observed. The crude lipase from BMV2 was partially purified by ultrafiltration and gel permeation chromatography with 24.64-fold purification. The K(m) and V(max) values for partially purified BMV2 lipase were found to be 1.56 mM and 5.62 micromoles/mg min. The metal ions Ca(2+), Mg(2+) and Mn(2+) had stimulatory effect on lipase activity, whereas Cu(2+), Fe(2+) and Zn(2+) strongly inhibited the lipase activity. EDTA and PMSF at 10mM concentration strongly inhibited the lipase activity. Non-ionic and anionic surfactants stimulated the lipase activity. BMV2 lipase was proved to be efficient in synthesis of ethyl butyrate ester under non-aqueous environment.

Biocidal capability optimization in organic-inorganic nanocomposites based on titania

Optimization of the interfacial agent content in biocidal titania-isotactic polypropylene nanocomposites is performed by evaluating their structural, thermal, optical, and biocidal properties. The balance between the photochemistry (photokilling) behavior and the thermal properties is achieved in the nanocomposites with an incorporation of 2 wt.% in inorganic nanoparticles (Tio2) using a compatibilizer content ranging from 50 to 80 wt.% with respect to the titania amount