Immobilized lipase from potential lipolytic microbes for catalyzing biodiesel production using palm oil as feedstock

Biodiesel has been regarded as a biodegradable and non-polluting fuel. Enzymatic transesterification reaction for manufacturing biodiesel from vegetable oils with alcohol is an attractive approach. However, the cost of enzyme remains a barrier for its industrial implementation. The aim of this research was the screening of lipase-producing microorganisms and the studies of potential lipase-mediated biodiesel production using palm oil as substrate. A total of 360 strains of bacteria, yeasts and fungi were isolated and screened from the samples of oil-contaminated soil and waste water. Among all the screened microbes, the potential lipolytic bacterium,  Staphylococcus warneri, unicellular yeast, Candida rugosa and filamentous fungus, Fusarium solani were selected because of their high specific  activities. The lipase-producing conditions were subsequently optimized by using palm oil as an inducer and lipase activities were compared for both hydrolytic and synthetic catalysis. C. rugosa lipase, which exhibited the highest potential for catalyzing the biodiesel production, was further  purified and immobilized on various hydrophobic supports. The catalysis of transesterification between methanol and palm oil by the C. rugosa immobilized lipases revealed that immobilized lipase from C. rugosa on Sepabeads EC-OD was the most promising for further development as a biocatalyst for the application of enzyme-catalyzed biodiesel synthesis.Key words: Screening, lipases, immobilization, biodiesel

Potential vegetable sources for biodiesel production:Cashew, coconut and cotton

This work presents a study on crude oil and biodiesel obtained from the seeds of the tropical plants Anacardium occidentale L (cashew), Cocos nucifera (coconut palm) and Gossypium hirsutum (upland cotton). The following crude oil and biodiesel physical-chemical properties were determined: acid number, iodine value, copper corrosivity, density and viscosity at different temperatures. Also, the chemical composition of the fatty acid methyl esters was measured using gas chromatography and a comparison was made with biodiesel from other sources reported in the literature. The analysis pointed out that cashew, coconut palm and upland cotton are potential sources for biodiesel production. Among the biodiesel types tested, cashew showed the highest oxidation stability

A glutathione transferase from Agrobacterium tumefaciens reveals a novel class of bacterial GST superfamily.

In the present work, we report a novel class of glutathione transferases (GSTs) originated from the pathogenic soil bacterium Agrobacterium tumefaciens C58, with structural and catalytic properties not observed previously in prokaryotic and eukaryotic GST isoenzymes. A GST-like sequence from A. tumefaciens C58 (Atu3701) with low similarity to other characterized GST family of enzymes was identified. Phylogenetic analysis showed that it belongs to a distinct GST class not previously described and restricted only in soil bacteria, called the Eta class (H). This enzyme (designated as AtuGSTH1-1) was cloned and expressed in E. coli and its structural and catalytic properties were investigated. Functional analysis showed that AtuGSTH1-1 exhibits significant transferase activity against the common substrates aryl halides, as well as very high peroxidase activity towards organic hydroperoxides. The crystal structure of AtuGSTH1-1 was determined at 1.4 Å resolution in complex with S-(p-nitrobenzyl)-glutathione (Nb-GSH). Although AtuGSTH1-1 adopts the canonical GST fold, sequence and structural characteristics distinct from previously characterized GSTs were identified. The absence of the classic catalytic essential residues (Tyr, Ser, Cys) distinguishes AtuGSTH1-1 from all other cytosolic GSTs of known structure and function. Site-directed mutagenesis showed that instead of the classic catalytic residues, an Arg residue (Arg34), an electron-sharing network, and a bridge of a network of water molecules may form the basis of the catalytic mechanism. Comparative sequence analysis, structural information, and site-directed mutagenesis in combination with kinetic analysis showed that Phe22, Ser25, and Arg187 are additional important residues for the enzyme's catalytic efficiency and specificity