The isolation and identification of new microalgal strains producing oil and carotenoid simultaneously with biofuel potential.

Taxonomy and phylogeny of twenty two microalgal isolates were examined using both universal and newly designed molecular primers. Among the isolates, Scenedesmus bijugus, Coelastrella sp., Auxenochlorella protothecoides, and Chlorella sp. were particularly promising in terms of producing lipids as measured by fatty acid methyl esters (FAME) analysis and significant concentration of carotenoids. A comparative experiment showed that S. bijugus and Chlorella sp. were the most promising candidates (L(-)(1)d(-)(1), with biomass) 174.77±6.75, 169.81±5.22mg, lipids 40.14±3.31, 39.72±3.89mg, lutein 0.47, 0.36mg, and astaxanthin 0.27, 0.18mg respectively. The fatty acids produced by these microalgal isolates were mainly palmitic, stearic, oleic, linoleic, and linolenic acid. The freshwater microalgal isolate S. bijugus be the most suitable isolate for producing biodiesel and carotenoids, due to high productivity of biomass, lipids, metabolites, and its suitable fatty acid profile.

Highly conserved Asp-204 and Gly-776 are important for activity of the quinoprotein glucose dehydrogenase of Escherichia coli and for mineral phosphate solubilization.

Gram-negative bacteria membrane-bound glucose dehydrogenase (m-GDH) has pyrroloquinoline quinone [PQQ (2,7,9,-tricarboxyl-1H-pyrrolo[2,3-f]quinoline-4,5-dione)] as its prosthetic group, transferring electrons to ubiquinone (UQ) in the membrane. Based on the sequence homology of the C-terminal catalytic domain (151-796 amino acid residues) we have modeled the 3D structure of Escherichia coli GDH. The geometrical parameters of the homology model structure, validated using the Ramachandran plot, revealed 95.8% of residues in the allowed regions and 2.2% of the residues in disallowed regions. From the model, we have identified five different amino acids that are specifically involved in maintaining the PQQ in the correct configuration along with a Ca(2+) ion in the active site, and two amino acids on the surface of the protein that might be involved in UQ binding or transfer of electrons to the UQ. Site-directed mutants R201A, D204A, E217L, E217A, R266Q, R266E, E591L, E591Q, E591K, L712W, L712R, G776K, G776D and G776L lost their GDH activity, while E217Q and G776A retained their function similar to that of wild-type GDH, both in terms of specific activity and mineral phosphate solubilization. Our conclusions are consistent with those previously based on model GDH produced by a different method and using a different template X-ray structure.

Transgenic expression of glucose dehydrogenase in Azotobacter vinelandii enhances mineral phosphate solubilization and growth of sorghum seedlings.

The enzyme quinoprotein glucose dehydrogenase (GDH) catalyses the oxidation of glucose to gluconic acid by direct oxidation in the periplasmic space of several Gram-negative bacteria. Acidification of the external environment with the release of gluconic acid contributes to the solubilization of the inorganic phosphate by biofertilizer strains of the phosphate-solubilizing bacteria. Glucose dehydrogenase (gcd) gene from Escherichia coli, and Azotobacter-specific glutamine synthetase (glnA) and phosphate transport system (pts) promoters were isolated using sequence-specific primers in a PCR-based approach. Escherichia coli gcd, cloned under the control of glnA and pts promoters, was mobilized into Azotobacter vinelandii AvOP and expressed. Sorghum seeds were bacterized with the transgenic azotobacters and raised in earthen pots in green house. The transgenic azotobacters, expressing E. coli gcd, showed improved biofertilizer potential in terms of mineral phosphate solubilization and plant growth-promoting activity with a small reduction in nitrogen fixation ability.

Ethyl methanesulfonate mutagenesis-enhanced mineral phosphate solubilization by groundnut-associated Serratia marcescens GPS-5.

Twenty-three bacterial isolates were screened for their mineral phosphate-solubilizing (MPS) ability on Pikovskaya and National Botanical Research Institute's phosphate (NBRIP) agar. The majority of the isolates exhibited a strong ability to solubilize hydroxyapatite in both solid and liquid media. The solubilization in liquid medium corresponded with a decrease in the pH of the medium. Serratia marcescens GPS-5, known for its biocontrol of late leaf spot in groundnut, emerged as the best solubilizer. S. marcescens GPS-5 was subjected to ethyl methanesulfonate (EMS) mutagenesis, and a total of 1700 mutants, resulting after 45 minutes of exposure, were screened on buffered NBRIP medium for alterations in MPS ability compared with that of the wild type. Seven mutants with increased (increased-MPS mutants) and 6 mutants with decreased (decreased-MPS mutants) MPS ability were isolated. All seven increased-MPS mutants were efficient at solubilizing phosphate in both solid and liquid NBRIP medium. Among the increased-MPS mutants, EMS XVIII Sm-35 showed the maximum (40%) increase in the amount of phosphate released in liquid medium compared with wild-type S. marcescens GPS-5, therefore, it would be a useful microbial inoculant in groundnut cultivation. EMS III Sm W, a nonpigmented mutant, showed the lowest solubilization of phosphate among the 6 decreased-MPS mutants.