Luigi De Martin

d-Phenylglycine and d-4-hydroxyphenylglycine methyl esters via penicillin G acylase catalysed resolution in organic solvents

Abstract Penicillin G acylase in organic solvents catalyses specifically the acylation of the l -enantiomers of methyl esters of phenylglycine and 4-hydroxyphenylglycine. Hydrolytic reactions are prevented by controlling the water activity of the system and no excess of acylating agent is required. The process leads to the facile isolation of the enantiomerically pure d -enantiomer, which is of practical use for the preparation of β-lactam antibiotics. Electrospray mass spectroscopy has been applied to the study of the enantioselectivity of the enzyme.

Penicillin G amidase in low-water media: immobilisation and control of water activity by means of celite rods

Abstract Penicillin G amidase (PGA) adsorbed on Celite rods (Celite R-640 from Fluka) catalyses, in toluene, the synthesis of amide bonds with yields >98% using equimolar concentrations of reactants. The method allows the easy recovery of the product and the recycling of the catalyst. Experimental data have pointed out that Celite rods adsorb water in a unusual but useful way, maintaining the water activity of the reaction system constant within defined ranges of water concentrations. Adsorption isotherms of Celite rods are reported and further applications of the method are proposed.

Organically modified xerogels as novel tailor-made supports for covalent immobilisation of enzymes (penicillin G acylase)

Abstract A novel application of organically modified silicates for covalent immobilisation of penicillin G acylase is reported. The immobilisation is efficient and the enzymatic preparation shows high specific activity and thermal stability. The technique opens new perspectives for the preparation of innovative tailor-made supports matching specific requirements of enzymatic processes.

A novel support for enzyme adsorption: properties and applications of aerogels in low water media

Abstract Aerogels, because of their porosity, have a great ability to adsorb water, and this characteristic was exploited to extend the applicability of aerogels for the adsorption and entrapment of hydrolases to be used in organic media. The applicability of aerogels as solid supports for immobilisation of the enzymes PGA, thermolysin and α-chymotrypsin was assayed. By controlling the distribution of water between the catalyst, the support and the reaction medium, aerogel preserves the catalytic activity of the enzymes and prevents hydrolytic reactions.

Activity of covalently immobilised PGA in water miscible solvents at controlled aw

Covalently immobilised penicillin G acylase is active in both apolar and water miscible solvents. Hydrated Celite R-640 added to water miscible solvents prevents the medium from stripping the water off the enzyme. The porous siliceous matrix has been used also for the dehydration and storage of the enzyme in apolar media.

Controlling the hydration of covalently immobilised penicillin G amidase in low-water medium: properties and use of Celite R-640

Abstract The study describes how Celite R-640 adsorbs liquid water in toluene and vapour water from a gas phase. In toluene, Celite R-640 is able to maintain the water activity ( a w ) constant within broad ranges of water concentrations. The a w values are strongly related to the original hydration of the Celite batches, but prolonged drying confers comparable and reproducible properties to the different batches. The use of Celite R-640 in controlling the hydration and activity of covalently immobilised PGA in toluene is reported.

High isolated yields in thermodynamically controlled peptide synthesis in toluene catalysed by thermolysin adsorbed on Celite R-640

An innovative immobilisation method that allows peptide synthesis to be performed even at equimolar concentrations, by controlling water activity, is reported.

Organically modified xerogels as supports for solid-phase chemistry

Organically modified xerogels (OMXNH2) can be used as an easy to handle and chemically stable support in solid-phase chemistry and are compatible with enzymatic transformations

Improved biotransformations on charged PEGA supports

PEGA supports functionalised with permanent charges show superior swelling properties in aqueous media when compared to neutral PEGA; a novel positively charged PEGA resin significantly improves penicillin G amidase (PGA) catalysed biotransformation on solid support, by favouring accessibility of the negatively charged enzyme.

High isolated yields in thermolysin-catalysed synthesis of Z-l-aspartyl-l-phenylalanine methyl ester in toluene at controlled water activity

Z-l-Aspartyl-l-phenylalanine methyl and ethyl esters were synthesised enzymatically in toluene by means of the zinc protease thermolysin adsorbed onto Celite R-640®, which is a porous support able to control the hydration of the protein. The conversion of the two derivatised amino acids into the desired products was complete, leading to >90% isolated yields. Moreover, working with equimolar concentrations of the reactants no purification steps were required. Thermolysin adsorbed onto Celite R-640® is shown to be a practical tool to synthesise biologically active peptides in organic media.