Interfacial activation-based molecular bioimprinting of lipolytic enzymes

Synthesis of sucrose 6-acetate by immobilized aspergillus Niger lipase imprinted with oleic acid and sorbitol

Biological and interfacial imprinting both were effective methods to improve the catalytic performance of lipase in organic solvent. Bioimprinting combined with interfacial activation of lipase was investigated for obtaining imprinted lipase with excellent catalytic performance. Enzymatic synthesis of sucrose-6-acetate in organic solvents to test the performance of imprinted lipase immobilized by adsorbing on macroporous resin. Lipase imprinted by substrate analog (oleic acid) then immobilization catalyzed the synthesis of sucrose-6-acetate with a 1.7 times increase in sucrose esterification rate compared to unimprinted immobilized lipase and a selectivity toward sucrose-6-acetate of 91.7 %. The sucrose esterification rate of reaction catalyzed by immobilized lipase was increased to 2.0 times with addition of sorbitol after imprinting by oleic acid. Imprinting by oleic acid and interfacial effect generated by oleic acid with sorbitol both induced zymoprotein secondary structure change that were conducive to enhance catalytic activity and stability of lipase in organic solvent.

Long chain capsaicin analogues synthetized by CALB-CLEAs show cytotoxicity on glioblastoma cell lines

Glioblastoma is one of the most lethal tumors, displaying striking cellular heterogeneity and drug resistance. The prognosis of patients suffering from glioblastoma after 5 years is only 5%. In the present work, capsaicin analogues bearing modifications on the acyl chain with long-chain fatty acids showed promising anti-tumoral activity by its cytotoxicity on U-87 and U-138 glioblastoma multiforme cells. The capsaicin analogues were enzymatically synthetized with cross-linked enzyme aggregates of lipase B from Candida antarctica (CALB). The catalytic performance of recombinant CALB-CLEAs was compared to their immobilized form on a hydrophobic support. After 72 h of reaction, the synthesis of capsaicin analogues from linoleic acid, docosahexaenoic acid, and punicic acid achieved a maximum conversion of 69.7, 8.3 and 30.3% with CALB-CLEAs, respectively. Similar values were obtained with commercial CALB, with conversion yields of 58.3, 24.2 and 22% for capsaicin analogues from linoleic acid, DHA and punicic acid, respectively. Olvanil and dohevanil had a significant cytotoxic effect on both U-87 and U-138 glioblastoma cells. Irrespective of the immobilization form, CALB is an efficient biocatalyst for the synthesis of anti-tumoral capsaicin derivatives. KEY POINTS: • This is the first report concerning the enzymatic synthesis of capsaicin analogues from docosahexaenoic acid and punicic acid with CALB-CLEAs. • The viability U-87 and U-138 glioblastoma cells was significantly affected after incubation with olvanil and dohevanil. • Capsaicin analogues from fatty acids obtained by CALB-CLEAs are promising candidates for therapeutic use as cytotoxic agents in glioblastoma cancer cells.

Bioimprinted lipase-catalyzed synthesis of medium- and long-chain structured lipids rich in docosahexaenoic acid for infant formula

Medium- and long-chain structured lipids (MLSLs) rich in docosahexaenoic acid (DHA) were obtained in shorter reaction time by acidolysis of single-cell oil (DHASCO) from Schizochytrium sp. with caprylic acid (CA) using a lipase bioimprinted with fatty acids as a catalyst. The conditions for preparation of the bioimprinted lipase for the acidolysis reaction were firstly optimized and the activity of the obtained lipase was 2.17 times higher than that of the non-bioimprinted. The bioimprinted lipase was then used as a catalyst and the reaction conditions were optimized. Under the optimal conditions, the equilibrium could be achieved in 4 h, and the total and sn-1,3 CA contents in the product were 29.18% and 42.34%, respectively, and the total and sn-2 DHA contents were 46.26% and 70.12%, respectively. Such MLSLs rich in sn-1,3 CA and sn-2 DHA are beneficial for DHA absorption, and thus have potential for use in infant formula.

Bioimprinting as a Receptor for Detection of Kwakhurin

Bioimprinting was performed against ovalbumin (OVA) to confer its binding cavities for kwakhurin (Kwa), an isoflavonoid, produced solely by Pueraria candollei var. mirifica (P. candollei). The characterization of bioimprinted-OVA (biOVA), evaluated by an enzyme-linked immunosorbent assay (ELISA), revealed that it functioned as a specific receptor for Kwa. Using biOVA, two systems, i.e., an indirect competitive ELISA (icELISA) and the even simpler and more rapid competitive enzyme-linked bioimprinted-protein assay (cELBIA), were developed as novel techniques for the quantitative analysis of Kwa in P. candollei and its related products. The two analysis methods were found to have limits of detection (LOD) of 4.0 and 2.5 µg/mL, respectively. The high reliability of the developed icELISA and cELBIA using biOVA was also demonstrated by various validation analyses. Subsequently, bioimprinting was performed using eight other proteins to investigate them as candidate scaffolds for the generation of binding cavities for Kwa. Interestingly, two bioimprinted-IgG monoclonal antibodies (biMAbs) recognized Kwa, but their original binding affinity to hapten was lost. That is, the MAbs obtained a new binding ability to Kwa in exchange for their original binding affinity, raising the possibility that biMAb could be alternatively used as a probe for the quantitative analysis of Kwa as well as biOVA. This is the first report of small molecules recognition by MAbs used as proteins for bioimprinting.

Physical behavior of KR-12 peptide on solid surfaces and Langmuir-Blodgett lipid films: Complementary approaches to its antimicrobial mode against S. aureus

Biophysical characterization of antimicrobial peptides helps to understand the mechanistic aspects of their action. The physical behavior of the KR-12 antimicrobial peptide (e.g. orientation and changes in secondary structure), was analyzed after interactions with a Staphylococcus aureus membrane model and solid surfaces. We performed antimicrobial tests using Gram-positive S. aureus (ATCC 25923) bacteria. Moreover, Langmuir-Blodgett experiments showed that the synthetic peptide can disturb the lipidic membrane at a concentration lower than the Minimum Inhibitory Concentration, thus confirming that KR-12/lipid interactions are involved. Partially- and fully-deactivated KR-12 hybrid samples were obtained by physisorption and covalent immobilization in chitosan/silica and glyoxal-rich solid supports. The correlation of Langmuir-Blodgett data with the α-helix formation, followed by FTIR-ATR in a frozen-like state, and the antimicrobial activity showed the importance of these interactions and conformation changes on the first step action mode of this peptide. This is the first time that material science (immobilization in solid surfaces assisted by FTIR-ATR analysis in frozen-like state) and physical (Langmuir-Blodgett/Schaefer) approaches are combined for exploring mechanistic aspects of the primary action mode of the KR-12 antimicrobial peptide against S. aureus.

Multi-Combilipases: Co-Immobilizing Lipases with Very Different Stabilities Combining Immobilization via Interfacial Activation and Ion Exchange. The Reuse of the Most Stable Co-Immobilized Enzymes after Inactivation of the Least Stable Ones

The lipases A and B from Candida antarctica (CALA and CALB), Thermomyces lanuginosus (TLL) or Rhizomucor miehei (RML), and the commercial and artificial phospholipase Lecitase ultra (LEU) may be co-immobilized on octyl agarose beads. However, LEU and RML became almost fully inactivated under conditions where CALA, CALB and TLL retained full activity. This means that, to have a five components co-immobilized combi-lipase, we should discard 3 fully active and immobilized enzymes when the other two enzymes are inactivated. To solve this situation, CALA, CALB and TLL have been co-immobilized on octyl-vinyl sulfone agarose beads, coated with polyethylenimine (PEI) and the least stable enzymes, RML and LEU have been co-immobilized over these immobilized enzymes. The coating with PEI is even favorable for the activity of the immobilized enzymes. It was checked that RML and LEU could be released from the enzyme-PEI coated biocatalyst, although this also produced some release of the PEI. That way, a protocol was developed to co-immobilize the five enzymes, in a way that the most stable could be reused after the inactivation of the least stable ones. After RML and LEU inactivation, the combi-biocatalysts were incubated in 0.5 M of ammonium sulfate to release the inactivated enzymes, incubated again with PEI and a new RML and LEU batch could be immobilized, maintaining the activity of the three most stable enzymes for at least five cycles of incubation at pH 7.0 and 60 °C for 3 h, incubation on ammonium sulfate, incubation in PEI and co-immobilization of new enzymes. The effect of the order of co-immobilization of the different enzymes on the co-immobilized biocatalyst activity was also investigated using different substrates, finding that when the most active enzyme versus one substrate was immobilized first (nearer to the surface of the particle), the activity was higher than when this enzyme was co-immobilized last (nearer to the particle core).

Lipase activation by molecular bioimprinting: The role of interactions between fatty acids and enzyme active site

Bioimprinting is an easy, sustainable and low-cost technique that promotes a printing of potential substrates on enzyme structure, inducing a more selective and stable conformation. Bioimprinting promotes conformational changes in enzymes, resulting in better catalytic performance. In this work, the effect of bioimprinting of Burkholderia cepacia lipase (BCL) and porcine pancreatic extracts (PPE) with four different fatty acids (lauric acid (C12:0), myristic acid (C14:0), palmitic acid (C16:0), and stearic acid (C18:0)) was investigated. The results demonstrated that the better bioimprinting effect was in BCL with lauric acid in esterification reaction, promoting BCL activation in which relative enzyme activity was 70 times greater than nonimprinted BCL. Bioimprinting results were influenced by the carbon chain length of fatty acids imprinted in the BCL, in which the effects were weaker with the chain increase. Molecular docking was performed to better understand the bioimprinting method. The results of these simulations showed that indeed all fatty acids were imprinted in the active site of BCL. However, lauric acid presented the highest imprinting preference in the active site of BCL, resulting in the highest relative activity. Furthermore, Fourier transform infrared (FTIR) analysis confirmed important variations in secondary structure of bioimprinting BCL with lauric acid, in which there was a reduction in the α-helix content and an increase in the β-sheet content that facilitated substrate access to the active site of BCL and led higher rigidity, resulting in high activity. Bioimprinted BCL with lauric acid showed excellent operational stability in esterification reaction, maintaining its original relative activity after five successive cycles. Thus, the results show that bioimprinting of BCL with lauric acid is a successful strategy due to its high catalytic activity and reusability.

Soluble expression of mature Rhizopus chinensis lipase in Escherichia coli and enhancement of its ester synthesis activity

The production of membrane-associated lipase from Rhizopus chinensis (RCL), which has a high ester synthesis activity and important potential applications, is difficult in heterologous expression system such as Escherichia coli and often leads to the formation of inclusion bodies. Here, we describe the soluble expression of mature RCL (mRCL) using maltose-binding protein (MBP) as a solubility-enhancing tag in the E. coli system. Although the MBP-mRCL fusion protein was soluble, mRCL was insoluble after removal of the MBP tag in E. coli BL21 (DE3). Using E. coli BL21 trxB (DE3) as an expression host, soluble mRCL was obtained and expression conditions were optimized. Furthermore, the ester synthesis activity of soluble mRCL was increased by detergent treatment and was found to be 3.5 and 1.5 times higher than those of the untreated enzyme and naturally occurring enzyme, respectively. Overall, this study provides a potential approach for producing active and soluble forms of eukaryotic lipases in a heterologous E. coli expression system.

Highly efficient production of chiral amines in batch and continuous flow by immobilized ω-transaminases on controlled porosity glass metal-ion affinity carrier

In this study, two stereocomplementary ω-transaminases from Arthrobacter sp. (AsR-ωTA) and Chromobacterium violaceum (Cv-ωTA) were immobilized via iron cation affinity binding onto polymer-coated controlled porosity glass beads (EziG™). The immobilization procedure was studied with different types of carrier materials and immobilization buffers of varying compositions, concentrations, pHs and cofactor (PLP) concentrations. Notably, concentrations of PLP above 0.1 mM were correlated with a dramatic decrease of the immobilization yield. The highest catalytic activity, along with quantitative immobilization, was obtained in MOPS buffer (100 mM, pH 8.0, PLP 0.1 mM, incubation time 2 h). Leaching of the immobilized enzyme was not observed within 3 days of incubation. EziG-immobilized AsR-ωTA and Cv-ωTA retained elevated activity when tested for the kinetic resolution of rac-α-methylbenzylamine (rac-α-MBA) in single batch experiments. Recycling studies demonstrated that immobilized EziG3-AsR-ωTA could be recycled for at least 16 consecutive cycles (15 min per cycle) and always affording quantitative conversion (TON ca. 14,400). Finally, the kinetic resolution of rac-α-MBA with EziG3-AsR-ωTA was tested in a continuous flow packed-bed reactor (157 μL reactor volume), which produced more than 5 g of (S)-α-MBA (>49% conversion, >99% ee) in 96 h with no detectable loss of catalytic activity. The calculated TON was more than 110,000 along with a space-time yield of 335 g L-1 h-1.

Novozym 435: the “perfect” lipase immobilized biocatalyst?

Novozym 435 (N435) is a commercially available immobilized lipase produced by Novozymes with its advantages and drawbacks.

How the Triton X-100 modulates the activity/stability of the Thermomyces lanuginose lipase: Insights from experimental and molecular docking approaches

The lipase and Triton X-100 mixture is common for stabilization, immobilization and application processes of these kinds of enzymes. The objective of this article was to study the structural behavior and catalytic performance of Thermomyces lanuginose lipase in the presence of Triton X-100 at 25 °C and different pHs. The structural changes were followed by circular dichroism, correlating them with the catalytic performance, which is reported as the initial lipase activity in the hydrolysis of p‑nitro phenyl butyrate at zero time and residual activity after 48 h of incubation in the absence or presence of surfactant, at the selected pHs. Computational simulations allowed to explain the correlations between the physicochemical changes and the formation of surfactant protein complex, leading to the elucidation of the main interactions that drive activity and stability of this lipase in presence of the Triton X-100 surfactant. Main results showed the Triton X-100-enzyme complex modulates the site active geometry, favoring a better substrate-enzyme adjustment, which influences the activity and stability at evaluated pHs. This study contributes to understand the effect of some additives commonly used to improve the biocatalytic performance on several applications for different industrial fields.

Facile fabrication of a recyclable nanobiocatalyst: immobilization of Burkholderia cepacia lipase on carbon nanofibers for the kinetic resolution of a racemic atenolol intermediate

Immobilization of surfactant treated Burkholderia cepacia lipase on the surface of carbon nanofibers was performed via two different methods: adsorption and covalent attachment. Simple adsorption of lipase on carbon nanofibers turned out to be a poor strategy, exhibiting an immobilization efficiency of 36%, while covalent coupling using 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide (EDC)/N-hydroxysuccinimide (NHS) showed better immobilization efficiency (56%). The nanobioconjugate fabricated using the latter method showed an eleven-fold increase in enzyme activity towards the hydrolysis of p-nitrophenyl palmitate and enhanced dispersion in organic solvents. At 80 °C, the half-life of lipase in the nanobioconjugate was almost 20 fold higher than that of free lipase, demonstrating its thermal stability. The as-prepared nanobioconjugate was reused for nine consecutive reaction cycles achieving 100% yield in the hydrolysis of p-nitrophenol palmitate but losing almost 50% of the initial activity after seven operational cycles. Finally, this heterogeneous nanobioconjugate was more active and enantioselective [C = 47.8, eep = 97.0 and E = 194] than free lipase [C = 35.4, eep = 97.1 and E = 88] towards the kinetic resolution of a racemic intermediate of atenolol yielding the S enantiomer, which signifies its importance as a nanobiocatalyst.

Engineering aspects of immobilized lipases on esterification: A special emphasis of crowding, confinement and diffusion effects

Cross-linked enzyme crystal (CLEC) and sol-gel entrapped pseudomonas sp. lipase were investigated for the esterification of lauric acid with ethanol by considering the effects of reaction conditions on reaction rate. The activation energy for the reaction was estimated to be 1097.58 J/mol and 181.75 J/mol for sol-gel and CLEC entrapped lipase respectively. CLEC lipase exhibited a marginal internal diffusion effect on reaction rate over sol-gel lipases and found to be interesting. The overall reaction mechanism was found to conform to the Ping Pong Bi Bi mechanism. The higher efficiency of sol-gel lipases over CLEC lipases in esterification reaction is mainly due to the combined effects of crowding, confinement and diffusional limitations.

Improved Performance of Magnetic Cross-Linked Lipase Aggregates by Interfacial Activation: A Robust and Magnetically Recyclable Biocatalyst for Transesterification of Jatropha Oil

Lipases are the most widely employed enzymes in commercial industries. The catalytic mechanism of most lipases involves a step called "interfacial activation". As interfacial activation can lead to a significant increase in catalytic activity, it is of profound importance in developing lipase immobilization methods. To obtain a potential biocatalyst for industrial biodiesel production, an effective strategy for enhancement of catalytic activity and stability of immobilized lipase was developed. This was performed through the combination of interfacial activation with hybrid magnetic cross-linked lipase aggregates. This biocatalyst was investigated for the immobilization of lipase from Rhizomucor miehei (RML). Under the optimal conditions, the activity recovery of the surfactant-activated magnetic RML cross-linked enzyme aggregates (CLEAs) was as high as 2058%, with a 20-fold improvement over the free RML. Moreover, the immobilized RML showed excellent catalytic performance for the biodiesel reaction at a yield of 93%, and more importantly, could be easily separated from the reaction mixture by simple magnetic decantation, and retained more than 84% of its initial activities after five instances of reuse. This study provides a new and versatile approach for designing and fabricating immobilized lipase with high activation and stability.

Obtaining a high activity subtilisin preparation by controlled thermal stress in n-octane

The use of enzymes in organic solvents has considerably widened their repertoire of applications. Such low water containing media also offer the possibility of carrying out enzymatic reactions at higher temperatures and enhancing reaction yields. The utility of such preparations is limited by the damage caused to the protein structure during freeze-drying. This work investigates the result of exposing the proteolytic enzyme subtilisin to high temperature in low water containing n-octane on its activity in aqueous and non-aqueous media. Exposing subtilisin at 90 °C for 5 h led to 18-fold improvement in its transesterification activity even at the normal assay temperature (37 °C) when compared with the untreated enzyme. The use of n-octane as the reaction medium was important as it helped to retain the three-dimensional architecture of the enzyme and should be considered while designing strategies for obtaining high activity preparations of other enzymes. Structural analysis using differential scanning fluorimetry showed that the enzyme lost its structure after heating in aqueous medium but retained it when heated in organic solvent. The simplicity and general applicability of the strategy should make it useful for obtaining highly active preparations of other enzymes as well.

Polyethylenimine: a very useful ionic polymer in the design of immobilized enzyme biocatalysts

This review discusses the possible roles of polyethylenimine (PEI) in the design of improved immobilized biocatalysts from diverse perspectives.

Formation of target-specific binding sites in enzymes: solid-phase molecular imprinting of HRP

Here we introduce a new concept for synthesising molecularly imprinted nanoparticles by using proteins as macro-functional monomers. For a proof-of-concept, a model enzyme (HRP) was cross-linked using glutaraldehyde in the presence of glass beads (solid-phase) bearing immobilized templates such as vancomycin and ampicillin. The cross-linking process links together proteins and protein chains, which in the presence of templates leads to the formation of permanent target-specific recognition sites without adverse effects on the enzymatic activity. Unlike complex protein engineering approaches commonly employed to generate affinity proteins, the method proposed can be used to produce protein-based ligands in a short time period using native protein molecules. These affinity materials are potentially useful tools especially for assays since they combine the catalytic properties of enzymes (for signaling) and molecular recognition properties of antibodies. We demonstrate this concept in an ELISA-format assay where HRP imprinted with vancomycin and ampicillin replaced traditional enzyme-antibody conjugates for selective detection of templates at micromolar concentrations. This approach can potentially provide a fast alternative to raising antibodies for targets that do not require high assay sensitivities; it can also find uses as a biochemical research tool, as a possible replacement for immunoperoxidase-conjugates.

Design and Preparation of Nano-Lignin Peroxidase (NanoLiP) by Protein Block Copolymerization Approach

This study describes the preparation of nanoprotein particles having lignin peroxidase (LiP) using a photosensitive microemulsion polymerization technique. The protein-based nano block polymer was synthesized by cross-linking of ligninase enzyme with ruthenium-based aminoacid monomers. This type polymerization process brought stability in different reaction conditions, reusability and functionality to the protein-based nano block polymer system when compared the traditional methods. After characterization of the prepared LiP copolymer nanoparticles, enzymatic activity studies of the nanoenzymes were carried out using tetramethylbenzidine (TMB) as the substrate. The parameters such as pH, temperature and initial enzyme concentration that affect the activity, were investigated by using prepared nanoLip particles and compared to free LiP. The reusability of the nano-LiP particles was also investigated and the obtained results showed that the nano-LiP particles exhibited admirable potential as a reusable catalyst.

Dual bioimprinting of Thermomyces lanuginosus lipase for synthesis of biodiesel

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High activity TLL is made by dually bioimprinting with substrate alcohol and a surfactant.

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TLL (28 U/g of oil) bioimprinted with only the surfactants could yield 99% biodiesel from soybean oil in about 4 h.

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Dually bioimprinted TLL (only 1.4 U/g of oil) was able to yield 99% biodiesel within 48 h

Use of biodiesel as an alternative to non-renewable sources of energy has become an attractive option in recent years. The enzymatic synthesis of biodiesel by transesterification of fats/oils with an alcohol is a much more sustainable route than the chemical method. However, cost effectiveness of the enzymatic route is a major barrier in its commercialization. In this work, a high activity biocatalyst design of Thermomyces lanuginosus lipase is made by dually bioimprinting it with substrate and a surfactant (which is believed to open up the lid covering the active site of the lipase) during precipitation of the lipase in organic solvent. When the lipase was bioimprinted with only the surfactants, 28 U of the enzyme/g of oil could yield 99% biodiesel from soybean oil in about 4 h. However, when dually bioimprinted even very low enzyme load 1.4 U/g of oil, yielded 99% biodiesel within 48 h.

Molecular bioimprinting of lipases with surfactants and its functional consequences in low water media

Lipases from Thermomyces lanuginosa (TLL), Candida rugosa (CRL) and Burkholderia cepacia (BCL) were obtained in the 'open lid' form by adding surfactant molecules like n-octyl-β-d-glucopyranoside (OG), hexadecyl trimethyl ammonium bromide (CTAB), Bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) and triton X-100 for this purpose. The enzymes were 'dried' by precipitating with 4× (v/v) excess of organic solvents. The imprint surfactant molecules were removed by extensive washing with organic solvents. TLL imprinted with 0.05% CTAB showed 11-fold increase in the transesterification activity and was a better preparation to kinetically resolve (±)-1-phenylethanol. Fluorescence emission spectra confirmed that Trp89 of the lid was indeed affected during bioimprinting. With CRL, bioimprinting with OG gave 7-fold increase in the transesterification rates and resulted in reversal of enantioselectivity of CRL and gave R-phenylethyl acetate instead of the S-product as with the unimprinted precipitate. Bioimprinted BCL was also a 7-fold better catalyst for transesterification as well as enantioselectivity.

Increasing importance of protein flexibility in designing biocatalytic processes

Enzymes require some flexibility for catalysis. Biotechnologists prefer stable enzymes but often this stabilization comes at the cost of reduced efficiency. Enzymes from thermophiles have low flexibility but poor catalytic rates. Enzymes from psychrophiles are less stable but show good catalytic rates at low temperature. In organic solvents enzymes perform poorly as the prior drying makes the enzyme molecules very rigid. Adding water or increasing reaction temperature improves flexibility and catalytic rates. In case of hydrolases, flexibility and enantioselectivity have interdependence. Understanding the complex role of protein flexibility in biocatalysis can help in designing biotechnological processes.

Additives enhancing the catalytic properties of lipase from Burkholderia cepacia immobilized on mixed-function-grafted mesoporous silica gel

Effects of various additives on the lipase from Burkholderia cepacia (BcL) immobilized on mixed-function-grafted mesoporous silica gel support by hydrophobic adsorption and covalent attachment were investigated. Catalytic properties of the immobilized biocatalysts were characterized in kinetic resolution of racemic 1-phenylethanol (rac-1a) and 1-(thiophen-2-yl)ethan-1-ol (rac-1b). Screening of more than 40 additives showed significantly enhanced productivity of immobilized BcL with several additives such as PEGs, oleic acid and polyvinyl alcohol. Effects of substrate concentration and temperature between 0–100 °C on kinetic resolution of rac-1a were studied with the best adsorbed BcLs containing PEG 20 k or PVA 18–88 additives in continuous-flow packed-bed reactor. The optimum temperature of lipase activity for BcL co-immobilized with PEG 20k found at around 30 °C determined in the continuous-flow system increased remarkably to around 80 °C for BcL co-immobilized with PVA 18–88.

Improved performance of Yarrowia lipolytica lipase-catalyzed kinetic resolution of (R,S)-2-octanol by an integrated strategy of interfacial activation, bioimprinting and immobilization

Yarrowia lipolytica lipase (YLL) demonstrated an (R)-enantiopreference for efficient resolution of (R,S)-2-octanol. The activity, enantioselectivity, the ratio of substrate to enzyme, acetaldehyde tolerance, and operational stability of YLL were improved by an integrated strategy of interfacial activation, bioimprinting, and immobilization. In comparison with the control, both the enzymatic activity and enantioselectivity increased by a factor of 8.85 and 2.75 by the integrated strategy, respectively. Fifty-one percentage of conversion with 220 of enantioselectivity was obtained using the immobilized YLL prepared by the integrated strategy at a ratio of 104 of substrate to enzyme loaded. The immobilized YLL retained 97% of its initial activity without a decrease in enantioselectivity after 10 successive reuse cycles. Together these results will result in a promising strategy with the YYL for efficient resolution of (R,S)-2-octanol in practice.

Enhanced catalysis of Yarrowia lipolytica lipase LIP2 immobilized on macroporous resin and its application in enrichment of polyunsaturated fatty acids

An immobilization strategy was employed to improve activity and operational stability of Yarrowia lipolytica lipase LIP2 (YlLIP2) by using macroporous resins as carrier. D152H, a cation-exchange resin, was the best support. Under the optimized conditions, the immobilization efficiency was 89.81% and the specific activity was 809,751 U/g, being 2.1-fold higher than that of the free lipase. Bioimprinting and interfacial activation were used to further boost the catalytic activity of YlLIP2, respectively enhanced 21.5-fold, 231.2% and 107.2% compared to the free, non-bioimprinted and non-interfacial-activated lipases. The immobilized lipase exhibited much better thermal and pH stability and broader substrate specificity; when used to enrich docosahexaenoic acid (DHA) from Chlorella protothecoides oil, it could increase 1.66-fold of DHA content and show good operational stability. These indicate that the immobilized YlLIP2 offers a promising approach for the enrichment of DHA.

Protein-associated water and secondary structure effect removal of blood proteins from metallic substrates

Removing adsorbed protein from metals has significant health and industrial consequences. There are numerous protein-adsorption studies using model self-assembled monolayers or polymeric substrates but hardly any high-resolution measurements of adsorption and removal of proteins on industrially relevant transition metals. Surgeons and ship owners desire clean metal surfaces to reduce transmission of disease via surgical instruments and minimize surface fouling (to reduce friction and corrosion), respectively. A major finding of this work is that, besides hydrophobic interaction adhesion energy, water content in an adsorbed protein layer and secondary structure of proteins determined the access and hence ability to remove adsorbed proteins from metal surfaces with a strong alkaline-surfactant solution (NaOH and 5 mg/mL SDS in PBS at pH 11). This is demonstrated with three blood proteins (bovine serum albumin, immunoglobulin, and fibrinogen) and four transition metal substrates and stainless steel (platinum (Pt), gold (Au), tungsten (W), titanium (Ti), and 316 grade stainless steel (SS)). All the metallic substrates were checked for chemical contaminations like carbon and sulfur and were characterized using X-ray photoelectron spectroscopy (XPS). While Pt and Au surfaces were oxide-free (fairly inert elements), W, Ti, and SS substrates were associated with native oxide. Difference measurements between a quartz crystal microbalance with dissipation (QCM-D) and surface plasmon resonance spectroscopy (SPR) provided a measure of the water content in the protein-adsorbed layers. Hydrophobic adhesion forces, obtained with atomic force microscopy, between the proteins and the metals correlated with the amount of the adsorbed protein-water complex. Thus, the amount of protein adsorbed decreased with Pt, Au, W, Ti and SS, in this order. Neither sessile contact angle nor surface roughness of the metal substrates was useful as predictors here. All three globular proteins behaved similarly on addition of the alkaline-surfactant cleaning solution, in that platinum and gold exhibited an increase, while tungsten, titanium, and stainless steel showed a decrease in weight. According to dissipation measurements with the QCM-D, the adsorbed layer for platinum and gold was rigid, while that for the tungsten, titanium, and stainless steel was much more flexible. The removal efficiency of adsorbed-protein by alkaline solution of SDS depended on the water content of the adsorbed layers for W, Ti, and SS, while for Pt and Au, it depended on secondary structural content. When protein adsorption was high (Pt, Au), protein-protein interactions and protein-surface interactions were dominant and the removal of protein layers was limited. Water content of the adsorbed protein layer was the determining factor for how efficiently the layer was removed by alkaline SDS when protein adsorption was low. Hence, protein-protein and protein-surface interactions were minimal and protein structure was less perturbed in comparison with those for high protein adsorption. Secondary structural content determined the efficient removal of adsorbed protein for high adsorbed amount.

Structural basis of the sensor-synthase interaction in autoinduction of the quorum sensing signal DSF biosynthesis

The diffusible signal factor (DSF)-dependent quorum sensing (QS) system adopts a novel protein-protein interaction mechanism to autoregulate the production of signal DSF. Here, we present the crystal structures of DSF synthase RpfF and its complex with the REC domain of sensor protein RpfC. RpfF is structurally similarity to the members of the crotonase superfamily and contains an N-terminal α/β spiral core domain and a C-terminal α-helical region. Further structural and mutational analysis identified two catalytic glutamate residues, which is the conserved feature of the enoyl-CoA hydratases/dehydratases. A putative substrate-binding pocket was unveiled and the key roles of the residues implicated in substrate binding were verified by mutational analysis. The binding of the REC domain may lock RpfF in an inactive conformation by blocking the entrance of substrate binding pocket, thereby negatively regulating DSF production. These findings provide a structural model for the RpfC-RpfF interaction-mediated QS autoinduction mechanism.