Gerard Gil

Phenoloxidases of the white-rot fungus Marasmius quercophilus isolated from an evergreen oak litter (Quercus ilex L.)

Abstract A white-rot basidiomycete, Marasmius quercophilus , was isolated from an evergreen oak litter. This fungus, which very thoroughly bleaches the whole leaf area, produces laccases, a property which has not been studied before. Except on a ground leaf medium, we did not reveal phenoloxidases other than laccases. M. quercophilus is able to transform many aromatic compounds which are by-products of lignin and tannin metabolism. We observed, for example, that lignin monomers, namely p -coumaryl, coniferyl, and sinapyl alcohols are oxidized at different rates by the extracellular crude enzyme extract. The highest production of laccases is obtained with shaking cultures on malt extract supplemented with Tween 80 (0.1%) and CuSO 4 (0.5 mg l −1 ). These enzymes have an optimum activity at 80°C and a stable activity at 40°C for 18 h. The extracellular crude enzyme extract medium contains three isoenzymes with pI values of 3.8, 3.5, and 3.2. It is able to significantly reduce the kappa number (21.2%) of a kraft pulp without inclusion of any mediator.

Lipase-catalyzed ester formation in organic solvents. Partial resolution of primary allenic alcohols

Abstract Candida cylindracea lipase catalyzes enantioselective esterifications of racemic primary allenic alcohols.

Microbial transformations: A stereoselective pathway to oxidize allenic alcohols

SummaryA bacterial strain, Pseudomonas aeruginosa (ATCC 17504), was selected to oxidize diversely substituted allenic alcohols. Primary α-allenic alcohols were oxidized to the corresponding acids with a ponderal yield varying from 60% to 90%. At the end of the experiment, the allenic chain was not altered, whereas absolute configurations were inverse for alcohol (S) and acid (R). This result corresponds to an enantiomeric separation of the initial racemic compound.An enantiomeric excess was also obtained with α-secondary and β-allenic alcohols. Substituents close to the allenic function decrease the ponderal yield.Existence of enzymes enable to recognize an axial chirality was shown.

Oxidation of α-allenic alcohols by yeast alcohol dehydrogenase

Abstract The kinetic constants (Km and Vm) of allenic alcohol oxidation by commercial alcohol dehydrogenase extracted from Saccharomyces cerevisiae (YADH) were compared to those measured for ethanol. For all the substrates DMF was used as solvent. Allenic chaining of butadienol does not induce any notable inhibition of the enzymatic reaction. The introduction of a substituent in the allenic alcohol molecule induces a decrease of enzymatic activity which becomes greater the closer substituent is located to the hydroxyl function.