Optimization of catalytic properties of Mucor racemosus lipase through immobilization in a biocompatible alginate gelatin hydrogel matrix for free fatty acid production: a sustainable robust biocatalyst for ultrasound-assisted olive oil hydrolysis

Immobilization is a key technology that improves the operational stability of enzymes. In this study, alginate-gelatin (Alg-Gel) hydrogel matrix was synthesized and used as immobilization support for Mucor racemosus lipase (Lip). Enzyme catalyzed ultrasound-assisted hydrolysis of olive oil was also investigated. Alg-Gel matrix exhibited high entrapment efficiency (94.5%) with a degradation rate of 42% after 30 days. The hydrolysis of olive oil using Alg-Gel-Lip increased significantly (P < 0.05) as compared to free Lip. Optimum pH and temperature were determined as pH 5.0 and 40 °C, respectively. The Vmax values for free and immobilized Lip were determined to be 5.5 mM and 5.8 mM oleic acid/min/ml, respectively, and the Km values were 2.2 and 2.58 mM/ml respectively. Thermal stability was highly improved for Alg-Gel-Lip (t1/2 650 min and Ed 87.96 kJ/mol) over free Lip (t1/2 150 min and Ed 23.36 kJ/mol). The enzymatic activity of Alg-Gel-Lip was preserved at 96% after four consecutive cycles and 90% of the initial activity after storage for 60 days at 4 °C. Alg-Gel-Lip catalyzed olive oil hydrolysis using ultrasound showed a significant (P < 0.05) increase in hydrolysis rate compared to free Lip (from 0.0 to 58.2%, within the first 2 h). In contrast to traditional methodology, using ultrasonic improved temperature-dependent enzymatic catalyzed reactions and delivered greater reaction yields. Results suggest that Alg-Gel-Lip biocatalyst has great industrial application potential, particularly for free fatty acid production. In addition, the combined use of enzyme and ultrasound has the potential of eco-friendly technology.

Evaluating enzyme stabilizations in calcium carbonate: Comparing in situ and crosslinking mediated immobilization

Enzyme immobilization using inorganic materials has been shown to preserve enzyme activity improving and improve their practical applications in biocatalytic process designs. Proper immobilization methods have been used to obtain high recycling and storage stability. In this study, we compared the activity and stability of in situ or crosslink-immobilized enzymes in a CaCO₃ biomineral carrier. More than 30% of the initial enzyme activity was preserved for both the systems after 180 days upon 15 activity measurements at room temperature, confirming the improved stability of these enzyme systems (100 mM phosphate buffer, pH 8.0); however, differences in enzyme loading, activity, and characteristics were observed for each of these methods. Each system exhibited efficacy of 80% and 20%, respectively. Based on the same amount of immobilized enzyme (0.2 mg), the specific activities of hydrolysis of p-nitrophenyl butyrate substrate at room temperature of in situ immobilized carboxyl esterase (CE) and crosslinked CE were 11.37 and 7.63 mM min^-1 mg^-1, respectively (100 mM phosphate buffer, pH 8.0). Moreover, based on the kinetic behavior, in situ immobilized CE exhibited improved catalytic efficiency (Vmax Km^-1) of the enzyme, exhibiting 4-fold higher activity and efficiency values than those of the CE immobilized in CaCO₃. This is the first study to describe the stabilization of enzymes in CaCO₃ and compare the enzyme kinetics and efficiencies between in situ immobilization and crosslinking in CaCO₃ carriers.

Facile preparation of aminosilane-alginate hybrid beads for enzyme immobilization: Kinetics and equilibrium studies

A simple, facile and potential platform for enzyme immobilization using alginate-based beads has been demonstrated by simultaneous gelation and modification of alginate using calcium chloride (CaCl₂) and 3-aminopropyltriethoxysilane (APTES). In this method, sodium alginate solution containing enzyme was simply dripped into a crosslinker solution containing CaCl₂ and APTES, leading to the formation of APTES-alginate hybrid beads (AP-beads). The optical observation, FT-IR analysis and amino group measurements provided evidence that APTES was successfully adsorbed to the alginate chain via electrostatic interaction. On the assumption that the binding of Ca²⁺ ion to polymannuronate residues of alginate via bidentate bridging coordination is competitive with APTES, the equilibrium isotherm and kinetics for the adsorption of APTES to AP-beads was found to follow extended Langmuir isotherm in binary system. Formate dehydrogenase (FDH) as a model enzyme was successfully immobilized in AP-beads and the immobilization yield of ca. 100% could be achieved under optimal conditions of CaCl₂ and APTES concentrations in crosslinker solution. Furthermore, the AP-beads were reused efficiently for 9 cycles without loss of FDH activity. The above results demonstrated that AP-beads were effective support for enzyme immobilization.

Monodisperse hybrid microcapsules with an ultrathin shell of submicron thickness for rapid enzyme reactions

In this study, we report a facile approach for the fabrication of monodisperse hybrid alginate/protamine/silica (APSi) microcapsules with an ultrathin shell of submicron thickness as enzyme encapsulation systems for rapid enzymatic reactions. Monodisperse water-in-oil (W/O) emulsions, which have been generated in microfluidics, are used as templates for preparing APSi microcapsules via internal/external gelation and biosilicification. The microcapsules allow highly-efficient encapsulation of model actives bovine serum albumin (∼99%) during the fabrication process. The hybrid shell with an ultrathin thickness of ∼420 nm provides fast mass transfer for the encapsulated model enzyme laccase to undergo rapid reaction. Moreover, this rigid hybrid shell also endows the encapsulated laccase with excellent reusability and storage stability. These ultrathin-shelled APSi microcapsules show great potential as efficient encapsulation systems for enzymes and biomolecules for their rapid reactions, and as delivery systems for actives in biomedical applications.

Immobilization of biocatalysts for enzymatic polymerizations: possibilities, advantages, applications

Biotechnology also holds tremendous opportunities for realizing functional polymeric materials. Biocatalytic pathways to polymeric materials are an emerging research area with not only enormous scientific and technological promise, but also a tremendous impact on environmental issues. Many of the enzymatic polymerizations reported proceed in organic solvents. However, enzymes mostly show none of their profound characteristics in organic solvents and can easily denature under industrial conditions. Therefore, natural enzymes seldom have the features adequate to be used as industrial catalysts in organic synthesis. The productivity of enzymatic processes is often low due to substrate and/or product inhibition. An important route to improving enzyme performance in non-natural environments is to immobilize them. In this review we will first summarize some of the most prominent examples of enzymatic polymerizations and will subsequently review the most important immobilization routes that are used for the immobilization of biocatalysts relevant to the field of enzymatic polymerizations.

Electrospun polystyrene-poly(styrene-co-maleic anhydride) nanofiber as a new aptasensor platform

Here, we report the use of an aptamer-immobilized electrospun polystyrene-poly(styrene-co-maleic anhydride) (PS-PSMA) nanofiber as a new aptasensor platform for protein detection. Two thrombin-binding aptamers (TBA29 and TBA15) were used as a model platform to facilitate efficient detection of thrombin in a sandwich manner. Thrombin concentration was measured by fluorescence microscopy and spectroscopy, in which aptamers were labeled with either fluorescein dye or quantum dots. The results indicated that thrombin was captured uniformly on the surface of the nanofiber. Using this sandwich-type biosensor, the minimum detectable concentration of thrombin was 10 pM, with a dynamic range of 0.1-50 nM, when quantum dots were used for labeling. In contrast, the limit of detection was 1 nM, with a dynamic range of 10-200 nM, when using fluorescein dye labeling. This aptamers-on-nanofiber-based biosensor showed 2500-fold higher sensitivity than a 96-microwell plate format, attributed mainly to the large surface area of the nanofibers. In addition, this novel platform also exhibited similar high sensitivity in the detection of exogenously added thrombin in diluted human serum. This aptamers-on-nanofiber system, which is competitive with other sensing platforms and clinically meaningful in terms of its detection limit, is expected to be useful for the detection of various other targets because of its ease of application and manipulation.