Carotenoid Production by a Novel Isolate of Microbacterium paraoxydans.

This study reports extraction and characterization of carotenoid pigments from Microbacterium paraoxydans, a non-photosynthetic bacterium, cultivated in Luria-Bertani (LB) medium. The isolate was identified to be moderately halo- and osmo-tolerant capable of withstanding high (~ 6%) salt and sugar (30% w/v sucrose, 20% w/v glucose) concentrations after a brief period of adaptation. The pigments were characterized using a combination of UV-Vis spectral analysis with the λmax at 407, 436 and 466 nm and ESI-MS with an m/z value at 536.44. The absorption profile of the pigments and their nature was influenced by carbon, nitrogen source and presence of salt in the growth medium. Highest level of pigment (~ 16 g kg dry wt cells-1) was produced in NH4Cl supplemented LB medium. The pigment displayed free radical scavenging, anticancer activity, characteristic of the plant carotenoids. Based on the accumulation of pigments under different conditions, a biochemical pathway for synthesis of neurosporene was proposed.

Biotransformation of sucrose into hexyl-α-D-glucopyranoside and -polyglucosides by whole cells of Microbacterium paraoxydans.

OBJECTIVE: To determine the transglycosylation activity of cell-bound enzymes from Microbacterium paraoxydans to catalyze the synthesis of hexyl-α-D-glucoside (HG) and -polyglucosides using sucrose as a glycosyl donor. RESULTS: Maximum HG yield (14.8 %) was achieved at 0.96 water activity in 12 h with sucrose at 0.5 M with lyophilized cells (equivalent to 8 IU α-glucosidase activity). The synthesized alkyl-glucosides and-polyglucosides were characterized by ESI-MS. Structural elucidation of the main product (purified by solid phase chromatography) was done by HSQC (2D NMR) which was confirmed as 1-hexyl-α-D-glucopyranoside. The synthesis was scaled up in a fed-batch reactor, with continuous feeding of whole cells every 6 h and a total yield of ~44 % was obtained for hexyl-glucoside and -polyglucosides under the optimized conditions. CONCLUSION: Synthesis of HG, hexyl di- and tri-glucosides has been achieved using a novel method.

In vitro antibacterial, antioxidant activity and total phenolic content of some essential oils.

In vitro antibacterial activity of 16 essential oils was investigated by disc diffusion method against two Gram positive bacteria Bacillus subtilis and Staphylococcus aureus and two Gram negative bacteria, Shigella flexneri and Escherichia coli. Oils of Cymbopogon citratus and Ocimum basilicum showed highest antibacterial activity. Gram positive bacteria were found to be more sensitive than Gram negative. Antioxidant activities were tested by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and ABTS radical cation decolourization assay while Folin-Ciocalteu method was used to determine the total phenolic content. In DPPH assay, highest antioxidant activity was observed in 0. basilicum oil followed by Azeratum conyzoides, A. marmelos and C. citratus, with percent inhibition and IC50 value ranging from 66.11-71.93% and 14.10-17.92 µl ml(-1) respectively. In ABTS assay, similar results were obtained but with higher percent inhibition which ranged from 67.48-76.23% and lower IC50 value (12.12-17.21 µ ml(-1)). Moreover, radical scavenging activity of essential oils was lower than that observed for the synthetic antioxidant BHA and BHT. The total phenolic content of the essential oils as GAE in mg 100 µl(-1) of EO was found to be highest in O. basilicum (0.406) oil followed byA. conyzoides (0.322), A. marmelos (0.238) and C. citratus (0.231). The results provide evidence that the oils of C. citratus and O. basilicum can be further commended for treatment of infections caused by these bacterial pathogens and are potential source of natural antioxidants having appreciable amount of total phenolic content.

Synthesis of hexyl α-glucoside and α-polyglucosides by a novel Microbacterium isolate.

Alkyl-glucosides and alkyl-polyglucosides are the new-generation biodegradable surfactants with good emulsifying and wetting properties. The α-forms of these glucosides occur in antibiotics and also stimulate nasal absorption of many drugs. In this paper, we report the synthesis of hexyl α-glucoside and α-polyglucosides using cell-bound α-glucosidase activity of a novel strain of Microbacterium paraoxydans. A number of cell-bound glycosyl hydrolase activities were detected in the isolate with the maximum hydrolytic activity of 180 IU g(-1) dry wt cells on p-nitrophenyl-α-D-glucopyranoside. In a micro-aqueous system, at a water activity of 0.69, 1.8 g l(-1) of hexyl α-glucoside (corresponding to about 25 % yield) was synthesized by whole cells with maltose and hexanol as substrates. The concentration was enhanced to 11 g l(-1) (~60 % yield) in a biphasic system at a water content of 60 %. (1)H and (13)C NMR spectra of the purified compound confirmed the synthesized product to be hexyl-α-D-glucopyranoside, while the presence of hexyl di- and tri-glucosides was confirmed by electrospray ionization mass spectrometry. The cell-driven synthesis makes this an extremely attractive alternative for synthesis of such compounds.

Synthesis and characterization of biologically significant 5,5'-(1,4-phenylene)bis(1-N-alkoxyphthalimido-3-aryl-2-pyrazoline) derivatives.

A facile synthesis of 5,5'-(1,4-phenylene)bis(3-aryl-2-pyrazolines) 4a-g has been achieved by the cyclo-addition reaction of hydrazine hydrate with bis-substituted chalcones 3a-g, which in turn were prepared by the Clasien-Schmidt condensation of p-substituted acetophenones 1a-g with terephthaldehyde. Condensation of 4a-g with omega-bromoalkoxyphthalimides 5a-b afforded the titled compounds 6a-n, some of which exhibited significant antimalarial as well as antimicrobial activity.