Immobilization of lipases for non-aqueous synthesis

Multipoint Immobilization at the Inert Center of Urease on Homofunctional Diazo-Activated Silica Gel: A Way of Restoring Room-Temperature Catalytic Sustainability for Perennial Utilization

At present, enzyme immobilization is a big issue. It improves enzyme stability, activity, specificity, or selectivity, particularly the enantioselectivity compared to the native enzymes, and by solving the separation problem, it helps in recovering the catalyst with good reusability as desired in vitro. Motivated by these facts, in this work, Jack bean urease (JBU) is immobilized on three-dimensional (3D)-network silica gel (SG) via multipoint covalent bonding employing dimethyldichlorosilane (DMDCS) and p-nitrophenol, respectively, as the second-generation silane-coupling reagent and spacer. The homofunctional diazo group appearing at the functionalized SG unit cell makes a diazo linkage at the inert center, the ortho position of the phenolic-OH of the tyrosine moiety, where all of the amino, thiol, phenol, imidazole, carboxy, etc., groups of the enzyme residues, including those that belong to the active site, remain intact. The coupling process, analyzed using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible spectroscopy (UV-vis), and fluorescence spectroscopy, occurs without molecular aggregation in borate buffer at pH 8.8 ± 0.4, which is much higher than the iso-electric point (pH 5.1) of the macromolecule where it becomes soluble. Eventually, the immobilization is maximize and also the native-enzyme activities are restored remarkably. The immobilized catalyst converts urea (0.0625-0.15 mmol L^-1) to ammonia appreciably (94.50 ± 1.5%) at 27 °C, and the efficiency is well comparable to that of the native enzyme (93.0 ± 0.4%). The efficiency gradually diminishes, coming down to 50% at the 40th cycle, and the enzyme returns to its native conformation within 72 h in tris-EDTA borate buffer at 27 °C for the next 40 cycles of reuse and so on. The efficiency becomes hindered by 8-10% in every 5th subsequent reuse to reach 50% on the 30th reuse, resulting in room-temperature catalytic sustainability of 90 days. The catalytic performances are well restored in rice extract and coconut water.

1,3-Dioleoyl-2-palmitoyl glycerol (OPO)-Enzymatic synthesis and use as an important supplement in infant formulas

1,3-dioleolyl-2-palmitate (OPO) is an important component of the human milk fat. Its unique fatty acid composition and distribution play an important role in proper infant growth and development. Owing to this, it has been attracting researchers and manufacturers to synthesize and commercialize OPO as an important human milk fat substitute added to infant formulas. In this review, the role of OPO in human milk, the benefits of OPO (sn-2 palmitate)-supplemented infant formulas over the conventional infant formulas on infant growth, and lipase-catalyzed synthesis of OPO are discussed. Over the last 20 years of research on the benefits of OPO (sn2 palmitate)-supplemented infant formulas are summarized. Similarly, studies carried out on lipase catalyzed production of OPO for the last 21 years (1999-2019) are also done focusing on the raw materials, sn1,3-regiospecific lipases, immobilization materials, and solvents used in the laboratory-scale experiments. In addition, OPO-based products currently in the market and future research trends are briefly covered in this review. PRACTICAL APPLICATIONS: This work focuses on lipase-catalyzed synthesis of 1,3-dioleoyl-2-palmitoylglycerol (the most abundant triacyl glycerol in human milk fat) and its benefits to infants when it is added in infant formulas. Over the last 20 years of published research from the literature are summarized and future research trends for efficient OPO synthesis are also covered. This will provide current and future researchers on the field with the necessary background information on OPO synthesis and design their research plans accordingly for cost-effective production of OPO and OPO-supplemented infant formulas.

Polymer Modification of Lipases, Substrate Interactions, and Potential Inhibition

An industrially important enzyme, Candida antarctica lipase B (CalB), was modified with a range of functional polymers including hydrophilic, hydrophobic, anionic, and cationic character using a "grafting to" approach. We determined the impact of polymer chain length on CalB activity by synthesizing biohybrids of CalB with each polymer at three different chain lengths, using reversible addition-fragmentation chain transfer (RAFT) polymerization. The activity of CalB in both aqueous and aqueous-organic media mixtures was significantly enhanced for acrylamide (Am) and N,N-dimethyl acrylamide (DMAm) conjugates, with activity remaining approximately constant in 25 and 50% ethanol solvent systems. Interestingly, the activity of N,N-dimethylaminopropyl-acrylamide (DMAPA) conjugates increased gradually with increasing organic solvent content in the system. Contrary to other literature reports, our study showed significantly diminished activity for hydrophobic polymer-protein conjugates. Functional thermal stability assays also displayed a considerable enhancement of retained activity of Am, DMAm, and DMAPA conjugates compared to the native CalB enzyme. Thus, this study provides an insight into possible advances in lipase production, which can lead to new improved lipase bioconjugates with increased activity and stability.

Production of trans-free interesterified fat using indigenously immobilized lipase

Enzymatic interesterification was carried out between high-oleic canola oil and fully hydrogenated soybean oil using indigenously immobilized Thermomyces lanuginosus lipas substrate concentration, moisture content of enzyme, and enzyme load. Interesterification resulted in a decrease in the concentration of tri-unsaturated and trisaturated TAG and an increase of mono- and di-saturated TAG as observed by reversed-phase HPLC. The alteration in TAG composition and the presence of new TAG species after interesterification was correlated with extended plasticity characterized by lower slip melting point with a significant change in functionality and consistency of the interesterified product. Thermal and structural properties of the blends before and after interesterification were assessed by differential scanning calorimetry (DSC), X-ray diffraction and polarized light microscopy. Trans-fat analysis indicated the absence of any trans fatty acid in the final interesterified product. The resultant interesterified products with varying slip melting points can be used in the formulation of healthier fat and oil products and address a critical industrial demand for trans free formulations for base-stocks of spreads, margarines, and confectionary fats.

Protein bioelectronics: a review of what we do and do not know

We review the status of protein-based molecular electronics. First, we define and discuss fundamental concepts of electron transfer and transport in and across proteins and proposed mechanisms for these processes. We then describe the immobilization of proteins to solid-state surfaces in both nanoscale and macroscopic approaches, and highlight how different methodologies can alter protein electronic properties. Because immobilizing proteins while retaining biological activity is crucial to the successful development of bioelectronic devices, we discuss this process at length. We briefly discuss computational predictions and their connection to experimental results. We then summarize how the biological activity of immobilized proteins is beneficial for bioelectronic devices, and how conductance measurements can shed light on protein properties. Finally, we consider how the research to date could influence the development of future bioelectronic devices.

Streamlined Preparation of Immobilized Candida antarctica Lipase B

Candida antarctica lipase B (CalB) was efficiently expressed (6.2 g L^-1) in Escherichia coli by utilizing an N-terminal tag cassette and the XylS/Pm expression system in a fed-batch bioreactor; subsequent direct binding to EziG from crude extracts resulted in an immobilized catalyst with superior activity to Novozym 435.

Modulation of the regioselectivity of Thermomyces lanuginosus lipase via biocatalyst engineering for the Ethanolysis of oil in fully anhydrous medium

Background

Enzymatic ethanolysis of oils (for example, high oleic sunflower oil containing 90% of oleic acid) may yield two different reaction products depending on the regioselectivity of the immobilized lipase biocatalyst. Some lipase biocatalysts exhibit a 1,3-regioselectivity and they produced 2 mols of fatty acid ethyl ester plus 1 mol of sn2-monoacylglycerol (2-MAG) per mol of triglyceride without the release of glycerol. Other lipase biocatalysts are completely non-regioselective releasing 3 mols of fatty acid ethyl ester and 1 mol of glycerol per mol of triglyceride. Lipase from Thermomyces lanuginosus (TLL) adsorbed on hydrophobic supports is a very interesting biocatalyst for the ethanolysis of oil. Modulation of TLL regioselectivity in anhydrous medium was intended via two strategies of TLL immobilization: a. - interfacial adsorption on different hydrophobic supports and b.- interfacial adsorption on a given hydrophobic support under different experimental conditions.

Results

Immobilization of TLL on supports containing divinylbenezene moieties yielded excellent 1,3-regioselective biocatalysts but immobilization of TLL on supports containing octadecyl groups yielded non-regioselective biocatalysts.

On the other hand, TLL immobilized on Purolite C18 at pH 8.5 and 30 °C in the presence of traces of CTAB yielded a biocatalyst with a perfect 1,3-regioselectivity and a very interesting activity: 2.5 μmols of oil ethanolyzed per min per gram of immobilized derivative. This activity is 10-fold higher than the one of commercial Lipozyme TL IM. Immobilization of the same enzyme on the same support, but at pH 7.0 and 25 °C, led to a biocatalyst which can hydrolyze all ester bonds in TG backbone.

Conclusions

Activity and regioselectivity of TLL in anhydrous media can be easily modulated via Biocatalysis Engineering producing very active immobilized derivatives able to catalyze the ethanolysis of triolein. When the biocatalyst was 1,3-regioselective a 33% of 2-monoolein was obtained and it may be a very interesting surfactant. When biocatalyst catalyzed the ethanolysis of the 3 positions during the reaction process, a 99% of ethyl oleate was obtained and it may be a very interesting drug-solvent and surfactant. The absence of acyl migrations under identical reaction conditions is clearly observed and hence the different activities and regioselectivities seem to be due to the different catalytic properties of different derivatives of TLL.

Design of a core–shell support to improve lipase features by immobilization

Different core–shell polymeric supports, exhbiting different featured, were produced and utilized in the immobilization and tuning of different lipases.

The halo-substituent effect on Pseudomonas cepacia lipase-mediated regioselective acylation of nucleosides: A comparative investigation

In this work, comparative experiments were explored to investigate the substrate specificity of Pseudomonas cepacia lipase in regioselective acylation of nucleosides carrying various substituents (such as the H, F, Cl, Br, I) at 2'- and 5-positions. Experimental data indicated that the catalytic performance of the enzyme depended very much on the halo-substituents in nucleosides. The increased bulk of 2'-substituents in ribose moiety of the nucleoside might contribute to the improved 3'-regioselectivity (90-98%, nucleosides a-d) in enzymatic decanoylation, while the enhancement of regioselectivity (93-99%) in 3'-O-acylated nucleosides e-h could be attributable to the increasing hydrophobicity of the halogen atoms at 5-positions. With regard to the chain-length selectivity, P. cepacia lipase displayed the highest 3'-regioselectivity toward the longer chain (C14) as compared to shorter (C6 and C10) ones. The position, orientation and property of the substituent, specific structure of the lipase's active site, and acyl structure could account for the diverse results.

Improved stability and enhanced efficiency to degrade chlorimuron-ethyl by the entrapment of esterase SulE in cross-linked poly (γ-glutamic acid)/gelatin hydrogel

Free enzymes often undergo some problems such as easy deactivation, low stability, and less recycling in biodegradation processes, especially in soil condition. A novel esterase SulE, which is responsible for primary degradation of a wide range of sulfonylurea herbicides by methyl or ethyl ester de-esterification, was expressed by strain Hansschlegelia sp. CHL1 and entrapped for the first time in an environment-friendly, biocompatible and biodegradable cross-linked poly (γ-glutamic acid)/gelatin hydrogel (CPE). The activity and stability of CPE-SulE were compared with free SulE under varying pH and temperature condition by measuring chlorimuron-ethyl residue. Meanwhile, the three-dimensional network of CPE-SulE was verified by scanning electron microscopy (SEM). The results showed that CPE-SulE obviously improved thermostability, pH stability and reusability compared with free SulE. Furthermore, CPE-SulE enhanced degrading efficiency of chlorimuron-ethyl in both soil and water system, especially in acid environment. The characteristics of CPE-SulE suggested the great potential to remediate chlorimuron-ethyl contaminated soils in situ.

Versatility of divinylsulfone supports permits the tuning of CALB properties during its immobilization

Properties of CALB has been modulated by immobilization on divinylsulfone (DVS) activated agarose beads under different conditions (pH 5–10).

Improved performance of lipases immobilized on heterofunctional octyl-glyoxyl agarose beads

A new heterofunctional support, octyl-glyoxyl agarose, is proposed in this study.

Characterization of supports activated with divinyl sulfone as a tool to immobilize and stabilize enzymes via multipoint covalent attachment. Application to chymotrypsin

DVS supports are very suitable to stabilize enzymes via multipoint covalent attachment.

Heterofunctional hydrophilic-hydrophobic porous silica as support for multipoint covalent immobilization of lipases: application to lactulose palmitate synthesis

Lipase-catalyzed synthesis of sugar esters, as lactulose palmitate, requires harsh conditions, making it necessary to immobilize the enzyme. Therefore, a study was conducted to evaluate the effect of different chemical surfaces of hierarchical meso-macroporous silica in the immobilization of two lipases from Pseudomonas stutzeri (PsL) and Alcaligenes sp. (AsL), which exhibit esterase activity. Porosity and chemical surface of silica supports, before and after functionalization and after immobilization, were characterized by gas adsorption and Fourier transform infrared (FTIR) spectroscopy. PsL and AsL were immobilized in octyl (OS), glyoxyl (GS), and octyl-glyoxyl silica (OGS). Hydrolytic activity, thermal and solvent stability, and sugar ester synthesis were evaluated with those catalysts. The best support in terms of expressed activity was OS in the case of PsL (100 IU g(-1)), while OS and OGS were the best for AsL with quite similar expressed activities (60 and 58 IU g(-1), respectively). At 60 °C in aqueous media the more stable biocatalysts were GS-PsL and OGS-AsL (half-lives of 566 and 248 h, respectively), showing the advantage of a heterofunctional support in the latter case. Lactulose palmitate synthesis was carried out in acetone medium (with 4% of equilibrium moisture) at 40 °C obtaining palmitic acid conversions higher than 20% for all biocatalysts, being the highest of those obtained with OGS-AsL and OS-PsL. Therefore, screening of different chemical surfaces on porous silica used as supports for lipase immobilization allowed obtaining active and stable biocatalyst to be employed in the novel synthesis of lactulose palmitate.

Lipase production by Botryosphaeria ribis EC-01 on soybean and castorbean meals: optimization, immobilization, and application for biodiesel production

The effects of soybean and castorbean meals were evaluated separately, and in combinations at different ratios, as substrates for lipase production by Botryosphaeria ribis EC-01 in submerged fermentation using only distilled water. The addition of glycerol analytical grade (AG) and glycerol crude (CG) to soybean and castorbean meals separately and in combination, were also examined for lipase production. Glycerol-AG increased enzyme production, whereas glycerol-CG decreased it. A 2(4) factorial design was developed to determine the best concentrations of soybean meal, castorbean meal, glycerol-AG, and KH2PO4 to optimize lipase production by B. ribis EC-01. Soybean meal and glycerol-AG had a significant effect on lipase production, whereas castorbean meal did not. A second treatment (2(2) factorial design central composite) was developed, and optimal lipase production (4,820 U/g of dry solids content (ds)) was obtained when B. ribis EC-01 was grown on 0.5 % (w/v) soybean meal and 5.2 % (v/v) glycerol in distilled water, which was in agreement with the predicted value (4,892 U/g ds) calculated by the model. The unitary cost of lipase production determined under the optimized conditions developed ranged from US$0.42 to 0.44 based on nutrient costs. The fungal lipase was immobilized onto Celite and showed high thermal stability and was used for transesterification of soybean oil in methanol (1:3) resulting in 36 % of fatty acyl alkyl ester content. The apparent K m and V max were determined and were 1.86 mM and 14.29 μmol min(-1) mg(-1), respectively.

A novel oriented immobilized lipase on magnetic nanoparticles in reverse micelles system and its application in the enrichment of polyunsaturated fatty acids

A novel oriented immobilized lipase was derived from Yarrowia lipolytica lipase LIP2 covalently immobilized on functionalized Fe3O4 magnetic nanoparticles (MNPs) in reverse micelles system (RMS). The activity recovery reached 382% compared with 29% in aqueous phase, and further ran up to 1425% under optimum conditions. (3-Aminopropyl) triethoxysilane (APTES) coated Fe3O4 nanoparticles were characterized by Fourier transform infrared (FT-IR) and X-ray diffraction (XRD). A significant alteration in the secondary structure of the lipase in RMS with a 15.5% increase of α-helix content and a 12.5% decrease of β-sheet content was detected by circular dichroism (CD). The immobilized lipase was employed to enrich polyunsaturated fatty acids in fish oil, a 90% increase of DHA content was obtained after 12h, and after 20 cycles of successive usage, it still remained over 80% of relative hydrolysis degree, which shows a good recyclability.

Enhanced ethyl butyrate production using immobilized lipase

In this study, the production of ethyl butyrate was investigated by using immobilized lipase enzyme in shake flasks. In order to determine optimum conditions for the production, response surface methodology was used. The model indicated the optimum conditions for maximum conversion (9.1%) at the 0.31 M substrate concentration, acid- alcohol molar ratio of 0.49, immobilized enzyme 25% (w/v) at 35°C, for 3 hours which were in good agreement with the experimental value. At the end of the 55 hours conversion was obtained as 61.3%. When Na2HPO4 was used in reaction medium conversion increased to 90.3% for 55 hours.

Enzymatically catalyzed synthesis of low-calorie structured lipid in a solvent-free system: optimization by response surface methodology

A kind of low-calorie structured lipid (LCSL) was obtained by interesterification of tributyrin (TB) and methyl stearate (St-ME), catalyzed by a commercially immobilized 1,3-specific lipase, Lipozyme RM IM from Rhizomucor miehei . The condition optimization of the process was conducted by using response surface methodology (RSM). The optimal conditions for highest conversion of St-ME and lowest content LLL-TAG (SSS and SSP; S, stearic acid; P, palmitic acid) were determined to be a reaction time 6.52 h, a substrate molar ratio (St-ME:TB) of 1.77:1, and an enzyme amount of 10.34% at a reaction temperature of 65 °C; under these conditions, the actually measured conversion of St-ME and content of LLL-TAG were 78.47 and 4.89% respectively, in good agreement with predicted values. The target product under optimal conditions after short-range molecular distillation showed solid fat content (SFC) values similar to those of cocoa butter substitutes (CBS), cocoa butter equivalent (CBE), and cocoa butters (CB), indicating its application for inclusion with other fats as cocoa butter substitutes.