Template enhanced activity of lipase accommodated in siliceous mesocellular foams

Lipases were adsorbed in siliceous mesocellular foams containing different amounts of residual template in the nanopores. It is found that the hydrolytic activities of the adsorbed lipases are increased with increasing the contents of template in the mesopores. The triacetin hydrolytic activity of the lipase adsorbed in the foam containing 46% of template can be 13 times higher than that of the lipase adsorbed in the foam without template in the nanopores, and its specific activity is about three times higher than that of the free lipase, showing the hyperactivation effect on lipase resulting from the interaction between the lipase and the surfactant in the nanopores. The immobilized lipase cross-linked with glutaraldehyde can retain up to 88% of its original activity after six hydrolysis reaction test. This work provides a new strategy to enhance the activity of immobilized lipase in mesoporous materials.     

Extraordinary enantiospecificity of lipase catalysis in organic media induced by purification and catalyst engineering

A purified lipase preparation from Candida rugosa was compared to its crude counterpart in anhydrous and slightly hydrated hydrophobic organic solvents. The purified lipase preparation was less active than the crude enzyme in dry n-heptane, whereas the presence of small concentrations of added water dramatically activated the purified enzyme but not the crude enzyme. Thus, in the presence of as little as 0.25 muL/mL of added water in n-heptane, the purified enzyme is over 230-fold more active and 6-fold more enantioselective than the dry enzyme suspension in the esterification of racemic 2-(4-chlorophenoxy)propionic acid with n-butanol. The reactivity and selectivity of this biocatalyst, however, was affected by coalescence of the enzyme preparation suspended in the wet organic solvent. Engineering the biocatalyst environment by dissolving the purified lipase in aqueous buffer and then adding this solution to n-heptane resulted in a precipitated enzyme preparation with smaller particle sizes that did not coalesce severely. In the presence of 5 muL/mL of water added with the enzyme, this pretreatment resulted in an activation over the dry, purified enzyme preparation of over 1800-fold and nearly enantiospecific catalysis (E > 100). Hence, by simply modifying the way enzymes are hydrated, dramatic activation of catalytic competency can be achieved. (c) 1996 John Wiley & Sons, Inc.     

Quantification analysis of yeast-displayed lipase

We describe a method for quantification of displayed lipase on yeast cell surface. The strategy uses an organophosphonate ester to irreversibly inhibit the active lipase and release a detectable fluorescent group. The amount of displayed lipase can be represented as “g/g cell” or “molecules/cell”. The results obtained correlated well with those obtained by existing methods. Therefore, this method is credible and will provide a powerful tool to promote research of lipase yeast surface display.     

Biodiesel production with immobilized lipase: A review

Fatty acid alkyl esters, also called biodiesel, are environmentally friendly and show great potential as an alternative liquid fuel. Biodiesel is produced by transesterification of oils or fats with chemical catalysts or lipase. Immobilized lipase as the biocatalyst draws high attention because that process is “greener”. This article reviews the current status of biodiesel production with immobilized lipase, including various lipases, immobilization methods, various feedstocks, lipase inactivation caused by short chain alcohols and large scale industrialization. Adsorption is still the most widely employed method for lipase immobilization. There are two kinds of lipase used most frequently especially for large scale industrialization. One is Candida antartica lipase immobilized on acrylic resin, and the other is Candida sp. 99–125 lipase immobilized on inexpensive textile membranes. However, to further reduce the cost of biodiesel production, new immobilization techniques with higher activity and stability still need to be explored.     

Immobilization by Adsorption of Hydrophobic Lipase Derivatives to Porous Polymer Beads for Use in Ester Synthesis

A novel procedure for attaching lipase to certain kinds of hydrophobic surfaces is described. The procedure involves covalent derivatization of the protein molecule by reaction in solution with a hydrophobic imidoester, aldehyde or activated polyethylene glycol. The resulting protein derivative is then allowed to adsorb onto an insoluble hydrophobic surface. Quantitative adsorption is observed and the enzyme is bound very strongly on the support The number and nature of the hydrophobic substituents introduced in the chemical derivatization step can be easily controlled. The adsorption step occurs spontaneously upon exposure of the modified protein to a variety of hydrophobic materials. The hydrophobic lipase derivative obtained by reaction with PEG activated with p-nirrophenyl chloroformate, for example, adsorbs readily onto polyacrylate and polystyrene beads, with most of its esterification activity in organic solvent intact. Its thermostability is also greatly enhanced. Derivatization of lipase with hydrophobic groups greatly enhances its esterification activity in organic solvent, and its immobilization in this manner enables the preparation of a highly reactive biocatalyst for biotechnological application.     

Expression and characterization of recombinant Rhizopus oryzae lipase for enzymatic biodiesel production

The Rhizopus oryzae lipase containing prosequence was expressed in Pichia pastoris. Recombinant lipase subunit showed a molecular mass of 32 kDa. The maximum activity of recombinant lipase obtained from Mut(s) recombinant was 90 IU/ml. The enzyme was stable in broad ranges of temperatures and pH, with the optimal temperature at 35 °C and pH 7.0. The crude recombinant R. oryzae lipase can be directly used for the transesterification of plant oils at high-water content of 60-100% (w/w) based on oil weight. The addition of 80% water to the transesterification systems resulted in the yield of methyl ester of 95%, 94% and 92% after 72 h using soybean oil, Jatropha curcas seed raw oil and Pistacia chinensis seed raw oil as raw material, respectively. These results indicate that the recombinant lipase is an effective biocatalyst for enzymatic biodiesel production.     

Magnetic Cross-Linked Enzyme Aggregates (mCLEAs) of Candida antarctica Lipase: An Efficient and Stable Biocatalyst for Biodiesel Synthesis

Enzyme-catalyzed production of biodiesel is the object of extensive research due to the global shortage of fossil fuels and increased environmental concerns. Herein we report the preparation and main characteristics of a novel biocatalyst consisting of Cross-Linked Enzyme Aggregates (CLEAs) of Candida antarctica lipase B (CALB) which are covalently bound to magnetic nanoparticles, and tackle its use for the synthesis of biodiesel from non-edible vegetable and waste frying oils. For this purpose, insolubilized CALB was covalently cross-linked to magnetic nanoparticles of magnetite which the surface was functionalized with –NH₂ groups. The resulting biocatalyst combines the relevant catalytic properties of CLEAs (as great stability and feasibility for their reutilization) and the magnetic character, and thus the final product (mCLEAs) are superparamagnetic particles of a robust catalyst which is more stable than the free enzyme, easily recoverable from the reaction medium and reusable for new catalytic cycles. We have studied the main properties of this biocatalyst and we have assessed its utility to catalyze transesterification reactions to obtain biodiesel from non-edible vegetable oils including unrefined soybean, jatropha and cameline, as well as waste frying oil. Using 1% mCLEAs (w/w of oil) conversions near 80% were routinely obtained at 30°C after 24 h of reaction, this value rising to 92% after 72 h. Moreover, the magnetic biocatalyst can be easily recovered from the reaction mixture and reused for at least ten consecutive cycles of 24 h without apparent loss of activity. The obtained results suggest that mCLEAs prepared from CALB can become a powerful biocatalyst for application at industrial scale with better performance than those currently available.     

An activity-based probe for high-throughput measurements of triacylglycerol lipases

Modulating the activity of lipases involved in the metabolism of plasma lipoproteins is an attractive approach for developing lipid raising/lowering therapies to treat cardiovascular disease. Identifying small molecule inhibitors for these membrane-active enzymes, however, is complicated by difficulties associated with measuring lipase activity and inhibition at the water–membrane interface; substrate and compound dynamics at the particle interface have the potential to confound data interpretation. Here, we describe a novel ELISA-based lipase activity assay that employs as “bait” a biotinylated active-site probe that irreversibly binds to the catalytic active-site serine of members of the triacylglycerol lipase family (hepatic lipase, lipoprotein lipase, and endothelial lipase) in solution with high affinity. Detection of “captured” (probe–enzyme) complexes on streptavidin-coated plates using labeled secondary antibodies to specific primary antibodies offers several advantages over conventional assays, including the ability to eliminate enzyme–particle and compound–particle effects; specifically measure lipase activity in complex mixtures in vitro; preferentially identify active-site-directed inhibitors; and distinguish between reversible and irreversible inhibitors through a simple assay modification. Using EL as an exemplar, we demonstrate the versatility of this assay both for high-throughput screening and for compound mechanism-of-action studies.     

Crosslinked enzyme aggregates in hierarchically-ordered mesoporous silica: a simple and effective method for enzyme stabilization

alpha-chymotrypsin (CT) and lipase (LP) were immobilized in hierarchically-ordered mesocellular mesoporous silica (HMMS) in a simple but effective way for the enzyme stabilization, which was achieved by the enzyme adsorption followed by glutaraldehyde (GA) crosslinking. This resulted in the formation of nanometer scale crosslinked enzyme aggregates (CLEAs) entrapped in the mesocellular pores of HMMS (37 nm), which did not leach out of HMMS through narrow mesoporous channels (13 nm). CLEA of alpha-chymotrypsin (CLEA-CT) in HMMS showed a high enzyme loading capacity and significantly increased enzyme stability. No activity decrease of CLEA-CT was observed for 2 weeks under even rigorously shaking condition, while adsorbed CT in HMMS and free CT showed a rapid inactivation due to the enzyme leaching and presumably autolysis, respectively. With the CLEA-CT in HMMS, however, there was no tryptic digestion observed suggesting that the CLEA-CT is not susceptible to autolysis. Moreover, CLEA of lipase (CLEA-LP) in HMMS retained 30% specific activity of free lipase with greatly enhanced stability. This work demonstrates that HMMS can be efficiently employed as host materials for enzyme immobilization leading to highly enhanced stability of the immobilized enzymes with high enzyme loading and activity.     

The crystal structure analysis of group B Streptococcus sortase C1: a model for the "lid" movement upon substrate binding

A unique feature of the class-C-type sortases, enzymes essential for Gram-positive pilus biogenesis, is the presence of a flexible “lid” anchored in the active site. However, the mechanistic details of the “lid” displacement, suggested to be a critical prelude for enzyme catalysis, are not yet known. This is partly due to the absence of enzyme-substrate and enzyme-inhibitor complex crystal structures. We have recently described the crystal structures of the Streptococcus agalactiae SAG2603 V/R sortase SrtC1 in two space groups (type II and type III) and that of its “lid” mutant and proposed a role of the “lid” as a protector of the active-site hydrophobic environment. Here, we report the crystal structures of SAG2603 V/R sortase C1 in a different space group (type I) and that of its complex with a small-molecule cysteine protease inhibitor. We observe that the catalytic Cys residue is covalently linked to the small-molecule inhibitor without lid displacement. However, the type I structure provides a view of the sortase SrtC1 lid displacement while having structural elements similar to a substrate sorting motif suitably positioned in the active site. We propose that these major conformational changes seen in the presence of a substrate mimic in the active site may represent universal features of class C sortase substrate recognition and enzyme activation.     

Modification of hydrophilicity/hydrophobicity of the microenvironment of lipase of Candida rugosa by dextrans

Replacing the lactose used in the commercial preparation of lipase from Candida rugosa by dextrans with different molecular weight, several preparations with enhanced activities in esterification of (R,S)-ibuprofen in organic medium were obtained. The presence of carbohydrates modifies the microenvironment of the enzyme and maintains the hydration of the biocatalyst. We can modulate the hydrophilic/hydrophobic balance on the surface of the biocatalyst creating non covalent enzyme-dextran complexes.     

Improved activity and stability of Rhizopus oryzae lipase via immobilization for citronellol ester synthesis in supercritical carbon dioxide

In present work, Rhizopus oryzae lipase immobilized on a film prepared using blend of hydroxylpropyl methyl cellulose (HPMC) and polyvinyl alcohol (PVA) was investigated for synthesis of citronellol esters with supercritical carbon dioxide (Sc-CO₂) as a reaction medium. The transesterification reaction was optimized for various reaction parameters like effect of molar ratio, acyl donor, time, temperature, enzyme concentration, effect of pressure and co-solvent to achieve the maximum yield of desired product. The results obtained signify remarkable increment (about eightfold) in the yield of citronellol acetate (91%) as compared to that of free lipase (11%) in Sc-CO₂. The developed biocatalytic methodology provides a substantial advantage of low biocatalyst loading (1.5%, w/v), lower reaction temperature (45 °C) and lower pressure (8 MPa) as compared to previous reports. The immobilization method has significantly enhanced the operational stability of lipase for ester synthesis under Sc-CO₂ conditions. The developed methodology was successfully applied for synthesis of three different industrially important citronellol esters namely citronellol acetate (91%), citronellol butyrate (98%), citronellol laurate (99%) with excellent yields using vinyl esters as acyl donor under Sc-CO₂ conditions. In addition, the immobilized biocatalyst was effectively recycled for three consecutive recycles.     

Magnetic Compass of Birds Is Based on a Molecule with Optimal Directional Sensitivity

The avian magnetic compass has been well characterized in behavioral tests: it is an “inclination compass” based on the inclination of the field lines rather than on the polarity, and its operation requires short-wavelength light. The “radical pair” model suggests that these properties reflect the use of specialized photopigments in the primary process of magnetoreception; it has recently been supported by experimental evidence indicating a role of magnetically sensitive radical-pair processes in the avian magnetic compass. In a multidisciplinary approach subjecting migratory birds to oscillating fields and using their orientation responses as a criterion for unhindered magnetoreception, we identify key features of the underlying receptor molecules. Our observation of resonance effects at specific frequencies, combined with new theoretical considerations and calculations, indicate that birds use a radical pair with special properties that is optimally designed as a receptor in a biological compass. This radical pair design might be realized by cryptochrome photoreceptors if paired with molecular oxygen as a reaction partner.     

Immobilization of lipase on cotton cloth using the layer-by-layer self-assembly technique

Lipase from Thermomyces lanuginosus was assembled into multiple layers on polyethylenimine treated cotton flannel cloth, utilising the enzymes property of forming bimolecular aggregates via layer-by-layer (LBL) immobilization technique. An increase in lipase activity with increasing enzyme layers confirmed lipase aggregation. A study to compare the activity of enzyme bound by classical LBL technique, containing alternate layers of polyethylenimine and lipase and the modified approach indicated above, showed that more enzyme was bound to cloth in the modified approach. A total of 13 U/cm² of enzyme were bound to cloth till the fifth layer whereas only 10.2 U/cm² were bound till the fifth bilayer in the classical approach. The successful assembly of lipase molecules has shown that this modified technique is a promising approach to immobilize enzymes that aggregate through hydrophobic interactions as nano-films on cloth.     

Characterization of <Emphasis Type="Italic">Mucor miehei</Emphasis> lipase immobilized on polysiloxane-polyvinyl alcohol magnetic particles

Mucor miehei lipase was immobilized on magnetic polysiloxane-polyvinyl alcohol particles by covalent binding. The resulting immobilized biocatalyst was recycled by seven assays, with a retained activity around 10% of its initial activity. K_m and V_max were respectively 228.3 M and 36.1 U mg of protein^–1 for immobilized enzyme. Whereas the optimum temperature remained the same for both soluble and immobilized lipase (45 °C), there was a shift in pH profiles after immobilization. Optimum pH for the immobilized lipase was 8.0. Immobilized enzyme showed to be more resistant than soluble lipase when assays were performed out of the optimum temperature or pH.     

In vitro evolved non-aggregating and thermostable lipase: structural and thermodynamic investigation

Rational and in vitro evolutionary approaches to improve either protein stability or aggregation resistance were successful, but empirical rules for simultaneous improvement of both stability and aggregation resistance under denaturing conditions are still to be ascertained. We have created a robust variant of a lipase from Bacillus subtilis named “6B” using multiple rounds of in vitro evolution. T_m and optimum activity temperature of 6B is 78 °C and 65 °C, respectively, which is ∼ 22 °C and 30 °C higher than that of wild-type lipase. Most significantly, 6B does not aggregate upon heating. Physical basis of remarkable thermostability and non-aggregating behavior of 6B was explored using X-ray crystallography, NMR and differential scanning calorimetry. Our structural investigations highlight the importance of tightening of mobile regions of the molecule such as loops and helix termini to attain higher thermostability. Accordingly, NMR studies suggest a very rigid structure of 6B lipase. Further investigation suggested that reduction/perturbation of the large hydrophobic patches present in the wild-type protein structure, decreased propensity of amino acid sequence for aggregation and absence of aggregation-prone intermediate during thermal unfolding of 6B can account for its resistance to aggregation. Overall, our study suggest that better anchoring of the loops with the rest of the protein molecule through mutations particularly on the sites that perturb/disturb the exposed hydrophobic patches can simultaneously increase protein stability and aggregation resistance.     

Selection of CalB immobilization method to be used in continuous oil transesterification: analysis of the economical impact

Enzymatic transesterification of triglycerides in a continuous way is always a great challenge with a large field of applications for biodiesel, bio-lubricant, bio-surfactant, etc. productions. The lipase B from Candida antarctica (CalB) is the most appreciated enzyme because of its high activity and its non-regio-selectivity toward positions of fatty acid residues on glycerol backbone of triglycerides. Nevertheless, in the field of heterogeneous catalysis, we demonstrated that the medium hydrophilic nature of the support used for its commercial form (Lewatit VPOC1600) is a limitation. Glycerol is adsorbed onto support inducing drastic decrease in enzyme activity. Glycerol would form a hydrophilic layer around the enzyme resulting in diffusional limitations during triglyceride transfer to the enzyme. Accurel MP, a very hydrophobic macroporous polymer of propylene, was found not to adsorb glycerol. Immobilization conditions using this support were optimized. The best support was Accurel MP1001 (particle size<1000 μm) and a pre-treatment of the support with acetone instead of ethanol enables the adsorption rate and the immobilized enzyme quantity to be maximized. An economical approach (maximization of the process net present value) was expanded in order to explore the impact of immobilization on development of an industrial packed bed reactor. The crucial ratio between the quantity of lipase and the quantity of support, taking into account enzyme, support and equipped packed bed reactor costs was optimized in this sense. The biocatalyst cost was found as largely the main cost centre (2-10 times higher than the investments for the reactor vessel). In consequence, optimal conditions for immobilization were a compromise between this immobilization yield (90% of lipase immobilized), biocatalyst activity, reactor volume and total investments.     

A structural investigation of complex I and I + III2 supercomplex from Zea mays at 11-13 Å resolution: Assignment of the carbonic anhydrase domain and evidence for structural heterogeneity within complex I

The projection structures of complex I and the I + III₂ supercomplex from the C₄ plant Zea mays were determined by electron microscopy and single particle image analysis to a resolution of up to 11 Å. Maize complex I has a typical L-shape. Additionally, it has a large hydrophilic extra-domain attached to the centre of the membrane arm on its matrix-exposed side, which previously was described for Arabidopsis and which was reported to include carbonic anhydrase subunits. A comparison with the X-ray structure of homotrimeric γ-carbonic anhydrase from the archaebacterium Methanosarcina thermophila indicates that this domain is also composed of a trimer. Mass spectrometry analyses allowed to identify two different carbonic anhydrase isoforms, suggesting that the γ-carbonic anhydrase domain of maize complex I most likely is a heterotrimer. Statistical analysis indicates that the maize complex I structure is heterogeneous: a less-abundant “type II” particle has a 15 Å shorter membrane arm and an additional small protrusion on the intermembrane-side of the membrane arm if compared to the more abundant “type I” particle. The I + III₂ supercomplex was found to be a rigid structure which did not break down into subcomplexes at the interface between the hydrophilic and the hydrophobic arms of complex I. The complex I moiety of the supercomplex appears to be only of “type I”. This would mean that the “type II” particles are not involved in the supercomplex formation and, hence, could have a different physiological role.     

A novel fluorescent timer based on bicistronic expression strategy in Caenorhabditis elegans

Fluorescent timers are useful tools for studying the spatial and temporal cellular or molecular events. Based on the trans-splicing mechanism in Caenorhabditis elegans, we constructed a “fluorescent timer” through bicistronic expression of two fluorescent proteins with different maturation times. When used in vivo, this “timer” changes its color over time and therefore can be used to monitor the activity of the targeted promoters in C. elegans. Using this “timer”, we have successfully traced the time-dependent activity of myo-3 promoter which drives expression in body wall muscle and vulval muscle. We found that the myo-3 promoter started to be active about 7 h after egg-laying and sustained its activity in the following hatching process. We have also determined the myo-3 promoter activity during larval development by this “timer”. We anticipate that more new “fluorescent timers” with variable time-resolution could be designed by bicistronic expression of different fluorescent protein pairs.     

Immobilization of lipase on hydrophobic nano-sized magnetite particles

As a tool for the stable enzyme reuse, enzyme immobilization has been studied for several decades. Surface-modified nano-sized magnetite (S-NSM) particles have been suggested as a support for the immobilization of enzyme in this study. Based on the finding that a lipase is strongly adsorbed onto a hydrophobic surface, NSM particles (8–12 nm) were made hydrophobic by binding of sodium dodecyl sulfate via a sulfate ester bond. Various types of measurements, such as transmission electron microscopy, X-ray diffraction, infrared spectroscopy, vibration sample magnetometer, and thermo gravimetric analysis, were conducted in characterizing S-NSM nanoparticles. S-NSM particles were used for the adsorption of porcine pancreas lipase (PPL). A dodecyl carbon chain is expected to form a spacer between the surface of the NSM and the lipase adsorbed. The immobilized PPL showed the higher specific activity of oil hydrolysis than that of free one. Immobilized PPL could be recovered by magnetic separation, and showed the constant activity during the recycles.