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The photochromic compound 2,6-bis(2-hydroxybenzilidene)cyclohexanone (PC) has been dissolved in some selected liquid amphiphiles: dibutyl, tributyl, bis-2-ethylhexyl, tris-2-ethylhexyl phosphate and bis-2-ethylhexyl amine. The aim was to explore its photophysical properties when embedded in the novel chemical environment provided by the amphiphilic solvents. UV-Vis spectra revealed different features depending on the solvent thus highlighting specific solvent-solute interactions and different chemical environments. All the alkylphosphate-based systems were found to be unstable; slow (days) changes in the absorption features due to the slow change in populations of the various species present in solution. Interestingly, the dissolution of PC into bis-2-ethylhexyl amine leads to stable solutions most probably due to the basic character of the solvent stabilising as major specie chalcone forms. Fluorescence spectra suggested the equilibrium between two species with different absorption and fluorescence properties. [ABSTRACT FROM AUTHOR]

The present study addresses comprehensively the problem of producing polyesters through sustainable processes while using fully renewable raw materials and biocatalysts. Polycondensation of bio-based dimethyl adipate with different diols was catalyzed by cutinase 1 from Thermobifida cellulosilytica (Thc_cut1) under solvent free and thin-film conditions. The biocatalyst was immobilized efficiently on a fully renewable cheap carrier based on milled rice husk. A multivariate factorial design demonstrated that Thc_cut1 is less sensitive to the presence of water in the system and it works efficiently under milder conditions (50 °C; 535 mbar) when compared to lipase B from Candida antarctica (CaLB), thus enabling energy savings. Experimental and computational investigations of cutinase 1 from Thermobifida cellulosilytica (Thc_cut1) disclosed structural and functional features that make this serine-hydrolase efficient in polycondensation reactions. Bioinformatic analysis performed with the BioGPS tool pointed out functional similarities with CaLB and provided guidelines for future engineering studies aiming, for instance, at introducing different promiscuous activities in the Thc_cut1 scaffold. The results set robust premises for a full exploitation of enzymes in environmentally and economically sustainable enzymatic polycondensation reactions. [ABSTRACT FROM AUTHOR]

Itaconic acid is a chemically versatile unsaturated diacid that can be produced by fermentation and potentially it can replace petrol-based monomers such as maleic and fumaric acids in the production of curable polyesters or new biocompatible functionalized materials. Unfortunately, due to the presence of the unsaturated CC bond, polycondensation of itaconic acid is hampered by cross reactivity and isomerization. Therefore, enzymatic polycondensations would respond to the need of mild and selective synthetic routes for the production of novel bio-based polymers. The present work analyses the feasibility of enzymatic polycondensation of diethyl itaconate and, for the first time, provides comprehensive solutions embracing both the formulation of the biocatalyst, the reaction conditions and the choice of the co-monomers. Computational docking was used to disclose the structural factors responsible for the low reactivity of dimethyl itaconate and to identify possible solutions. Surprisingly, experimental and computational analyses revealed that 1,4-butanediol is an unsuitable co-monomer for the polycondensation of dimethyl itaconate whereas the cyclic and rigid 1,4-cyclohexanedimethanol promotes the elongation of the oligomers. [ABSTRACT FROM AUTHOR]

There is an enormous potential for synthesizing novel bio-based functionalized polyesters under environmentally benign conditions by exploiting the catalytic efficiency and selectivity of enzymes. Despite the wide number of studies addressing in vitro enzymatic polycondensation, insufficient progress has been documented in the last two decades towards the preparative and industrial application of this methodology. The present study analyses bottlenecks hampering the practical applicability of enzymatic polycondensation that have been most often neglected in the past, with a specific focus on solvent-free processes. Data here presented elucidate how classical approaches for enzyme immobilization combined with batch reactor configuration translate into insufficient mass transfer as well as limited recyclability of the biocatalyst. In order to overcome such bottlenecks, the present study proposes thin-film processes employing robust covalently immobilized lipases. The strategy was validated experimentally by carrying out the solvent-free polycondensation of esters of adipic and itaconic acids. The results open new perspectives for enlarging the applicability of biocatalysts in other viscous and solvent-free syntheses. [ABSTRACT FROM AUTHOR]

Efficient immobilisation protocols are the result of perfect matching of factors depending on the enzyme, the process and the support for immobilisation. Physical–chemical phenomena, such as partition, solvation and diffusion, strongly affect the efficiency of the biocatalyst in each specific reaction system. Therefore, tailored solutions must be developed for each specific process of interest. Indeed, direct investigation of what occurs at the molecular level in a reaction catalysed by an immobilised enzyme is a quite formidable task and observed differences in the performance of immobilised biocatalysts must be interpreted very carefully. In any study dealing with enzyme immobilisation the prerequisite is the rigorous planning and reporting of experiments, being aware of the complexity of these multi-phase systems. [ABSTRACT FROM AUTHOR]

Lipases are the most widely used enzymes in synthetic organic chemistry. The search for efficient methods for immobilization of enzymes has emerged an important field of interest in order to increase their activity, stability and to facilitate their recovery because of the industrial application of lipases. In this study, the lipase immobilization by entrapment in sol-gel matrices was investigated to study the effect of enzymes, supports and enzyme/support ratios. [ABSTRACT FROM AUTHOR]