Influence of the hydrophobicity of lipase isoenzymes from Candida rugosa on its hydrolytic activity in reverse micelles

Degradable polycaprolactone nanoparticles stabilized via supramolecular host–guest interactions with pH-responsive polymer-pillar[5]arene conjugates

Smart nano-carriers such as micelles, vesicles or nanoparticles constructed from amphiphilic polymers promise a new generation of drug delivery systems featuring localized and controlled release.

Biocatalytic synthesis of flavor ester "pentyl valerate" using Candida rugosa lipase immobilized in microemulsion based organogels: effect of parameters and reusability

Pentyl valerate was synthesized biocatalytically using Candida rugosa lipase (CRL) immobilized in microemulsion based organogels (MBGs). The optimum conditions were found to be pH 7.0, temperature of 37°C, ratio of concentration of water to surfactant (Wo) of 60, and the surfactant sodium bis-2-(ethylhexyl)sulfosuccinate (AOT) for MBG preparation. Although kinetic studies revealed that the enzyme in free form had high affinity towards substrates (K_m = 23.2 mM for pentanol and 76.92 mM for valeric acid) whereas, after immobilization, the K_m values increased considerably (74.07 mM for pentanol and 83.3 mM for valeric acid) resulting in a slower reaction rate, the maximum conversion was much higher in case of immobilized enzyme (~99%) as compared to free enzyme (~19%). Simultaneous effects of important parameters were studied using response surface methodology (RSM) conjugated with Box-Behnken design (BBD) with five variables (process parameters), namely, enzyme concentration, initial water content (Wo), solvent used for MBG preparation, substrate ratio and time, and response as the final product formation, that is, pentyl valerate (%). The MBGs were reused for 10 consecutive cycles for ester synthesis. Efficacy of AOT/isooctane as dehydrating agent for extracting excess water from MBGs was found to exert a positive effect on the esterification reaction.

Structure-guided modification of Rhizomucor miehei lipase for production of structured lipids

To improve the performance of yeast surface-displayed Rhizomucor miehei lipase (RML) in the production of human milk fat substitute (HMFS), we mutated amino acids in the lipase substrate-binding pocket based on protein hydrophobicity, to improve esterification activity. Five mutants: Asn87Ile, Asn87Ile/Asp91Val, His108Leu/Lys109Ile, Asp256Ile/His257Leu, and His108Leu/Lys109Ile/Asp256Ile/His257Leu were obtained and their hydrolytic and esterification activities were assayed. Using Discovery Studio 3.1 to build models and calculate the binding energy between lipase and substrates, compared to wild-type, the mutant Asp256Ile/His257Leu was found to have significantly lower energy when oleic acid (3.97 KJ/mol decrease) and tripalmitin (7.55 KJ/mol decrease) were substrates. This result was in accordance with the esterification activity of Asp256Ile/His257Leu (2.37-fold of wild-type). The four mutants were also evaluated for the production of HMFS in organic solvent and in a solvent-free system. Asp256Ile/His257Leu had an oleic acid incorporation of 28.27% for catalyzing tripalmitin and oleic acid, and 53.18% for the reaction of palm oil with oleic acid. The efficiency of Asp256Ile/His257Leu was 1.82-fold and 1.65-fold that of the wild-type enzyme for the two reactions. The oleic acid incorporation of Asp256Ile/His257Leu was similar to commercial Lipozyme RM IM for palm oil acidolysis with oleic acid. Yeast surface-displayed RML mutant Asp256Ile/His257Leu is a potential, economically feasible catalyst for the production of structured lipids.

Investigating pH and Cu (II) effects on lipase activity and enantioselectivity via kinetic and spectroscopic methods

For Candida rugosa lipase (CRL) catalyzed hydrolysis of racemic 1-phenethyl acetate, both the weakly acidic pH (pH 6.0) and the addition of 1 mM copper (II) ion enhanced the enzyme activity and enantioselectivity (E value) about twofold, as compared with that under neutral pH and noadditive conditions. The decrease of activation free energy (DeltaG) and increase of k(cat)(R)/k(cat)(S) at weakly acidic pH and/or in the presence of copper (II) characterized the kinetic behavior of CRL. On the other hand, for providing reasonable insights into the catalytic mechanism and the structural basis for enantioselectivity alteration, spectroscopic techniques were employed to probe conformational changes of the enzyme in each medium assayed. The fluorescence emission spectra revealed that pH and copper (II) might exert different effects on the microenvironment of Trp residue and thereby on the protein conformation, which could be further verified by UV-visible and Raman spectra. The conformational modulation of CRL associated with either pH or copper (II) concentration in the reaction medium could be attributed to the flexible and sensitive conformation of the enzyme, which is responsible for the significant variation of apparent activity and enantioselectivity with the tuning of biocatalyst microenvironment.

Candida Rugosa lipase reactions in nonionic w/o-microemulsion with a technical surfactant

In enzyme catalysis there is a great interest in finding suitable organic media for less water soluble substrates in order to increase the substrate concentration and therefore the reaction rates. These requirements are fulfilled by using w/o-microemulsions as reaction media. The influences of pH, temperature, water concentration and the kinetic parameters of Candida Rugosa Lipase in a nonionic w/o-microemulsion with a surfactant of technical grade, Marlipal O13-60, are presented. In an example the enantiospecific esterification of racemic menthol with propionic anhydride using this nonionic microemulsion likely to be affordable in large scale applications is shown. For a continuous process an ultrafiltration unit is attached to a reactor within a loop. In this way, the reverse micelles containing the enzymes can be separated from the oil, containing the product, and reused afterwards.

Bioorganic reactions in microemulsions

Water-in-oil microemulsions, or reverse micelles, are being evaluated as a reaction medium for a variety of enzymatic reactions. These systems have many potential biotechnological applications. Important examples are the use of various lipase microemulsion systems for hydrolytic or synthetic reactions. This review illustrates the biotechnological applications of microemulsions as media for bioorganic reactions. The principal focus is on lipase catalyzed processes.