Commercial Immobilized Lipases Research Articles

Innovative approach for semi‐continuous production of puerarin palmitate via transesterification with novel immobilized lipase

BackgroundPuerarin, a flavonoid abundantly found in the roots of Pueraria lobata, exhibits antioxidant, anti-cancer, anti-inflammatory, and anti-aging properties. Despite its numerous benefits, the low bioavailability of puerarin hinders its widespread industrial application. To improve this, flavonoid acylation is required. Lipase is a biocatalyst primarily used for flavonoid acylation; immobilized lipase is preferred given the limited stability of free lipase. Although research on flavonoid acylation for structural modification is actively being conducted, there is a need to explore continuous production for enhancing the industrial application of flavonoid esters. Therefore, in this study, we aimed to produce puerarin palmitate innovatively by selecting an effective lipase, developing an immobilized lipase, characterizing the enzymatic reaction, and designing a semi-continuous reactor system.ResultsLipase from Thermomyces lanuginosus (TL) was found to be the most suitable for the synthesis of puerarin palmitate; it was successfully immobilized on glutaraldehyde-activated silica gel (GASG). TL GASG showed greater solvent, thermal, and operational stability than those of commercial immobilized lipases. Furthermore, TL GASG use resulted in a puerarin palmitate conversion rate of 97.17% within 3 h. Additionally, the reusability of TL GASG for this reaction was higher than that of commercially available immobilized lipases. Upon using a semi-continuous reactor, the cumulative conversion rate of puerarin palmitate remained above 85% after more than ten substrate injections.ConclusionsThe results support the feasibility of the continuous production of flavonoid esters, underscoring their diverse industrial applications. A biorefinery strategy is anticipated to be proposed to utilize P. lobata extract biomass for flavonoid ester production. Moreover, optimizing continuous reactors through statistical experimental design is expected to enhance flavonoid ester production efficiency; these aspects will be explored in future research.Graphical

Fatty Acid Epoxidation on Enzymes: Experimental Study and Modeling of Batch and Semibatch Operation

Biolubricants, plasticizers, bio-based rigid foams, and non-isocyanate polyurethanes can be made in a green way from epoxidized fatty acids. The classical technology for fatty acid epoxidation requires a reaction carrier, which acts as the real epoxidation agent. The process is complicated and involves a safety risk because of the appearance of percarboxylic acids. Therefore, the direct epoxidation of fatty acids in the presence of an immobilized enzyme is an attractive pathway to epoxidized fatty acids. Oleic acid was used as the model compound is this work, and commercial immobilized lipase Novozym 435 was used as the catalyst and hydrogen peroxide as the epoxidation agent. Batch and semibatch operation modes were tested in a laboratory-scale stirred tank reactor. The experimental results showed that almost complete conversions of the double bonds in oleic acid were achievable under isothermal batch and semibatch operation, with low concentrations of ring-opening byproducts. Semibatch operation gave an improvement of the product yield. Mathematical modeling of the experimental data was based on the reaction stoichiometry OA + HP → POA + W and OA + POA → EOA + OA, where OA = oleic acid, HP = hydrogen peroxide, POA = peroleic acid, W = water, and EOA = epoxized OA. Rate equations for the formation of peroleic acid and epoxide were derived, and the numerical values of the kinetic and adsorption parameters were estimated with nonlinear regression analysis. The reactor models consisted of ordinary differential equations, which were solved numerically during the parameter estimation until the optimal parameter values were reached. The model gave a very good description of the experimental data.

Continuous Production of Dietetic Structured Lipids Using Crude Acidic Olive Pomace Oils.

Crude olive pomace oil (OPO) is a by-product of olive oil extraction. In this study, low-calorie structured triacylglycerols (TAGs) were produced by acidolysis of crude OPO with medium-chain fatty acids (caprylic, C8:0; capric, C10:0) or interesterification with their ethyl ester forms (C8EE, C10EE). These new TAGs present long-chain fatty acids (L) at position sn-2 and medium-chain fatty acids (M) at positions sn-1,3 (MLM). Crude OPO exhibited a high acidity (12.05-28.75% free fatty acids), and high contents of chlorophylls and oxidation products. Reactions were carried out continuously in a packed-bed bioreactor for 70 h, using sn-1,3 regioselective commercial immobilized lipases (Thermomyces lanuginosus lipase, Lipozyme TL IM; and Rhizomucor miehei lipase, Lipozyme RM IM), in solvent-free media at 40 °C. Lipozyme RM IM presented a higher affinity for C10:0 and C10EE. Lipozyme TL IM preferred C10:0 over C8:0 but C8EE over C10EE. Both biocatalysts showed a high activity and operational stability and were not affected by OPO acidity. The New TAG yields ranged 30-60 and the specific productivity ranged 0.96-1.87 g NewTAG/h.g biocatalyst. Lipozyme RM IM cost is more than seven-fold the Lipozyme TL IM cost. Therefore, using Lipozyme TL IM and crude acidic OPO in a continuous bioreactor will contribute to process sustainability for structured lipid production by lowering the cost of the biocatalyst and avoiding oil refining.

Enzymatic Synthesis of Ascorbyl Palmitate in a Rotating Bed Reactor.

Ascorbyl palmitate, an ascorbic acid ester, is an important amphipathic antioxidant that has several applications in foods, pharmaceuticals, and cosmetics. The enzymatic synthesis of ascorbyl palmitate is very attractive, but few efforts have been made to address its process scale-up and implementation. This study aimed at evaluating the enzymatic synthesis of ascorbyl palmitate in a rotating basket reactor operated in sequential batches. Different commercial immobilized lipases were tested, and the most suitable reaction conditions were established. Among those lipases studied were Amano Lipase PS, Lipozyme® TL IM, Lipozyme® Novo 40086, Lipozyme® RM IM and Lipozyme® 435. Initially, the enzymes were screened based on previously defined synthesis conditions, showing clear differences in behavior. Lipozyme® 435 proved to be the best catalyst, reaching the highest values of initial reaction rate and yield. Therefore, it was selected for the following studies. Among the solvents assayed, 2-methyl-2-butanol and acetone showed the highest yields, but the operational stability of the catalyst was better in 2-methyl-2-butanol. The tests in a basket reactor showed great potential for large-scale application. Yields remained over 80% after four sequential batches, and the basket allowed for easy catalyst recycling. The results obtained in basket reactor are certainly a contribution to the enzymatic synthesis of ascorbyl palmitate as a competitive alternative to chemical synthesis. This may inspire future cost-effectiveness studies of the process to assess its potential as a viable alternative to be implemented.

Biocatalytic synthesis of dioctyl sebacate in toluene using an immobilised lipase

Sebacic esters have excellent lubricity, thermal stability, and biodegradability and therefore are widely used as aerospace lubricants, metal working oil, or engine oil. They are mainly produced by chemical synthesis which, however, may cause environmental pollution, its enzymatic synthesis represents a more environmentally friendly alternative. A few reports have described the synthesis of sebacic esters employing immobilised lipases, but these biocatalytic reactions were exclusively carried out in solvent-free systems and thus, could have been limited by slow reaction rates and high reaction temperatures due to poor enzyme dispersion, low substrate solubility, and high viscosity of the reaction mixture. The current study investigated the biosynthesis of dioctyl sebacate in toluene by Novozym 435, a commercial immobilised lipase. The reaction parameters were investigated using the single factor approach and an orthogonal array design. The optimal conditions obtained were as follows: 10 mL toluene, sebacic acid,1 mmol (202.25 mg); molar ratio of sebacic acid to 1-octanol, 1:3; Novozym 435, 0.03 g; 4 Å molecular sieves, 1.5 g; reaction temperature, 40 °C; reaction time, 30 h. A dioctyl sebacate conversion rate of 93% was achieved under these optimal conditions. In particular, the addition of molecular sieves to the reaction mixture markedly improved the product yield. The reaction temperature was low enough to make the operation easy and energy-efficient and therefore, well suited for large-scale production.

Enzymatic interesterification of beef tallow/coconut oil blends to produce a superior margarine base stock

SummaryThe effect enzymatic interesterification (EIE) on the functional performances of beef tallow (BT) blended with coconut oil (CO) in varying proportions was investigated. BT and three different proportions of CO, containing 20%, 30% or 40% CO were interesterified in a solvent‐free system with a commercial immobilised lipase, Lipozyme TL IM. The interesterified oils (IOs) were also processed into margarines, and their textural properties, microstructure as well as their sensory properties, were determined. The IO with 40% CO has the best properties for margarine production, with a low content of high melting‐point triacylglycerols, which should minimise the ‘waxy’ mouth‐feel of BT‐based margarines. The fat in IO‐based margarine (M‐IO) was mainly in the β′ crystal form and the crystals were more evenly distributed than in BT‐based margarine (M‐BT). A sensory and textural evaluation determined that the texture of M‐IO was more compact, and that its colour and flavour were better than M‐BT. The IO obtained may be used as a base oil to replace BT in margarine and has potential application in the margarine industry.

Argan Oil as a Rich Source of Linoleic Fatty Acid for Dietetic Structured Lipids Production.

Argan oil is rich in long-chain unsaturated fatty acids (FA), mostly oleic and linoleic, and natural antioxidants. This study addresses the production of low-calorie structured lipids by acidolysis reaction, in a solvent-free system, between caprylic (C8:0; system I) or capric (C10:0; system II) acids and argan oil, used as triacylglycerol (TAG) source. Three commercial immobilized lipases were tested: Novozym® 435, Lipozyme® TL IM, and Lipozyme® RM IM. Higher incorporation degree (ID) was achieved when C10:0 was used as acyl donor, for all the lipases tested. Lipozyme® RM IM yielded the highest ID for both systems (28.9 ± 0.05 mol.% C10:0, and 11.4 ± 2.2 mol.% C8:0), being the only catalyst able to incorporate C8:0 under the reaction conditions for biocatalyst screening (molar ratio 2:1 FA/TAG and 55 °C). The optimal conditions for Lipozyme® RM IM in system II were found by response surface methodology (66 °C; molar ratio FA/TAG of 4:1), enabling to reach an ID of 40.9 mol.% of C10:0. Operational stability of Lipozyme® RM IM in system II was also evaluated under optimal conditions, after eight consecutive 24 h-batches, with biocatalyst rehydration between cycles. The biocatalyst presented a half-life time of 103 h.

Study of enzymatic production of biodiesel using vegetable oils and commercial ethanol

Biodiesel is a combination of alkyl fatty acid esters generated by a catalyst and supported by acid, basic, or enzymatic processes from vegetable oils to short-chain alcohols such as methanol or ethanol. However, the high costs for raw materials utilising vegetable oil of food grade have made it commercially impracticable to produce this biofuel. Research has therefore expanded with residual oil indicating that biomass from household and industrial waste has been technically feasible. The outcome of this investigation coincides with the enzyme production study of biodiesel utilising residual oil and ethanol, according to this principle. In esterification of commercial oleic acid, the behaviour of commercial immobilised lipase from CAL-B was examined and the variables affecting the process were investigated. Based on the results presented and discussed in this paper, the use of immobilized Candida antarctica lipase type B (CAL-B) for biodiesel production is more viable when using acidic substrates, since the best results were achieved with such raw materials and with a reaction rate comparable to esterification with an acid catalyst. The results of this work showed that the enzymatic esterification of commercial oleic acid with ethanol provided a conversion of 87.3% within 60 minutes of reaction, at a temperature of 30 °C, in a stoichiometric proportion and without adsorption of water. Both biocatalysts showed good stability, which produced over 80% conversion and 60 minutes of reaction and could be repeated without substantial loss of activity for at least 10 consecutive occasions

Immobilized lipase-catalyzed transesterification for synthesis of biolubricant from palm oil methyl ester and trimethylolpropane.

The present study reports the effects of three commercial immobilized lipases namely Novozyme 435 from Candida antarctica lipase B (CALB), Lipozyme TL IM from Thermomyces lanuginosus and Lipozyme RM IM from Rhizomucor miehei on the production of trimethylolpropane (TMP) ester from high oleic palm methyl ester (HO-PME) and TMP. The TMP ester is a promising base oil for biolubricants that are easily biodegradable and non-toxic to humans and the environment. Enzymatic catalysts are insensitive to free fatty acid (FFA) content, hence able to mitigate the side reactions and consequently reduce product separation cost. The potential of these enzymes to produce TMP ester in a solvent-free medium was screened at various reaction time (8, 23, 30 and 48h), operating pressure (0.1, 0.3 and 1.0mbar) and enzyme dosage (1, 3, 5 and 10% w/w). The reaction was conducted at a constant temperature of 70°C and a molar ratio of 3.9:1 (HO-PME: TMP). Novozyme 435 produced the highest yield of TMP ester of 95.68 ± 3.60% under the following conditions: 23h reaction time, 0.1mbar operating pressure and 5% w/w of enzyme dosage. The key lubrication properties of the produced TMP ester are viscosity index (208 ± 2), pour point (- 30 ± - 2°C), cloud point (- 15 ± - 2°C), onset thermal degradation temperature (427.8°C), and oxidation stability, RPVOT (42 ± 4min). The properties of the TMP ester produced from the enzymatic transesterification are comparable to other vegetable oil-based biolubricants produced by chemical transesterification.

Ultrasound-assisted enzymatic synthesis of xylitol fatty acid esters in solvent-free conditions

A commercial immobilized lipase was successfully used for the synthesis of five xylityl acyl esters by means of the esterification of free fatty acids (caprylic, capric, lauric and myristic, respectively) with xylitol under solvent-free conditions. Ultrasound-assistance was shown to be a key tool to overcome the handicap imposed by both the mutual immiscibility of fatty acids and xylitol substrates, and the semisolid character of the initial reaction mixtures. In such semisolid systems, ultrasonic irradiation may enable the transport of substrate molecules to the enzyme catalytic-site, leading to the efficient synthesis of xylityl fatty ester (e.g. up to 95% yield after 90 min at 40 °C), with xylityl monoacyl ester and xylitol diacyl ester appearing as the main products (greater than 96%), assessed by HPLC and NMR analyses. The separation of products was carried out by heating and simple centrifugation of the reaction medium, which was possible due to different densities of the resulting fractions.

A simplified kinetic model to describe the solvent‐free enzymatic synthesis of wax esters

AbstractBACKGROUNDThe use of biotechnological processes at industrial scale is a promising tool to replace conventional synthesis as an efficient and eco‐friendly technology. For that purpose, the kinetic modelling of an in‐lab optimized enzymatic process prior to scaling‐up is of great utility.RESULTSIn this work, a kinetic model for the solvent‐free synthesis of cetyl laurate, myristate, palmitate and stearate using different commercial immobilized lipases has been developed. In order to describe the esterification process of the cetyl esters separately and as a mixture similar to natural spermaceti, a pseudo‐first‐order kinetic has been proposed and tested. A relation between the inverse values of the kinetic constant and the amount of biocatalyst has been observed. The effect of temperature on the reaction rate can be accurately described by the Arrhenius equation except for immobilized Thermomyces lanuginosus, which appears to be less resistant to temperatures above 70 °C.CONCLUSIONLow deviations between experimental and predicted values (R2 ≥ 0.99) indicate that this pseudo‐first‐order kinetic model can be considered valid for the data range studied. In addition, the reaction rate of spermaceti can be successfully predicted through a weighted average of the kinetic constants obtained during the synthesis of each cetyl ester. This simple but accurate kinetic model for describing the solvent‐free enzymatic biosynthesis of wax esters from spermaceti may contribute to extending the application of lipases as industrial catalysts. © 2021 Society of Chemical Industry (SCI).

Evaluation of continuous ethyl ester synthesis from acid soybean oil using a dual immobilized enzyme system

The use of non-edible oils, waste oils, and animal fats have been investigated as a low-cost feedstock for biodiesel (fatty acid alkyl esters) synthesis. However, these alternative raw materials have some drawbacks due to the high content of free fatty acid (FFA). This work aimed to study the continuous enzymatic ethyl esters synthesis, in a solvent-free system, from the reaction of acid soybean oil (acid value, AV, of 0.5, 8.5, 50, and 90) and ethanol using a dual commercial immobilized lipase system (Novozym 435®, Lipozyme TL IM®, Lipozyme RM IM®). Initially, a dual lipase system was used in a single packed-bed reactor (PBR). The blend of Lipozyme TL IM and Novozym 435 had a positive synergistic effect on biodiesel synthesis: an increase of 76% in ethyl ester content was observed after 2 h using refined soybean oil. However, a reduction in the yield was observed in longer reaction times (25 h). Therefore, a continuous reaction system, operated with two different catalytic beds, was investigated. The use of two series reactors allowed high ethyl ester yield (>90%) and high acid conversion (>90%). The reaction using acid soybean oil (50 AV), and Lipozyme RM IM and Novozym 435 reached an ethyl ester content of 95% and 70% after 2 and 25 h, respectively. The results showed that using two different commercial immobilized lipases in intercalated packed-bed reactors enhanced biodiesel synthesis from acid soybean oil. The enzymatic system allows a high fatty acid conversion present in the acidic oil into ethyl ester.

Optimized Scalable Synthesis of Chiral Iridium Pyridyl‐Phosphinite (Pyridophos) Catalysts

AbstractIridium catalysts with chiral P,N ligands have greatly enhanced the scope of asymmetric olefin hydrogenation because they do not require a coordinating group near the C=C bond like Rh and Ru catalysts. Pyridophos ligands, possessing a conformationally restricted annulated pyridine framework linked to a phosphinite group, proved to be particularly effective, inducing high enantioselectivities in the hydrogenation of a remarkably broad range of substrates. Here we report the development of an efficient scalable synthesis for the two most versatile Ir‐pyridophos catalysts, derived from 2‐phenyl‐8‐hydroxy‐5,6,7,8‐tetrahydroquinoline or the analogue with a five‐membered carbocyclic ring, respectively, by modification and optimization of the original synthetic route. The optimized route renders both catalysts readily accessible in multi‐gram quantities in analytically pure form in overall yields of 26–37 %, starting from acetophenone and cyclopentanone or cyclohexanone, respectively. A major advantage of the new synthesis is the efficient and practical kinetic resolution of the late‐stage pyridyl alcohol intermediates with commercial immobilized Candida antarctica lipase B, giving access to both enantiomers of these catalysts as essentially enantiopure compounds. The catalysts are obtained as crystalline solids, which are air‐stable and can be stored for years at −20 °C without notable decomposition.

Performing under pressure: esterification activity of dry fermented solids in subcritical and supercritical CO2.

Lipases are often used in immobilized form, but commercial immobilized lipases are costly. An alternative is to produce lipases in solid-state fermentation, dry the solids and then use the "dry fermented solids" (DFS) directly. We produced DFS by growing Burkholderia contaminans on a mixture of sugarcane bagasse and sunflower seed meal and used the DFS to esterify oleic acid with ethanol in subcritical and supercritical CO2 at 40°C. Compared to a control without CO2 at atmospheric pressure, subcritical CO2 at 30bar improved esterification activity 1.2-fold. Higher pressures, including supercritical pressures up to 150bar, reduced activity to less than 80% of the control. At 30bar, the esterification activity was improved a further 1.8-fold with the addition of 9% water (i.e. 9g water per 100g oleic acid) to the reaction medium. A subcritical CO2 atmosphere, with the addition of a small amount of water, improved the esterification activity of DFS containing lipases of Burkholderia contaminans.

Interfacial microenvironment for lipase immobilization: Regulating the heterogeneity of graphene oxide

Compared to the traditional chemical reduction method, a green and efficient strategy was successfully applied to regulate the surface heterogeneity of graphene oxide (GO). In this work, different kinds of amino acids were used to reduce and modify GO. The reduction and adsorption disparities of amino acids contributed to the difference of structural heterogeneity in terms of density, thermal tolerance and disorder of the oxygen-containing groups of GO. The modification also resulted in discrepancies in surface properties of the GO samples, such as hydrophobicity and surface charge. The functionalized GO was employed as a carrier for the immobilization of lipase from Thermomyces lanuginosus (lipase TL). The storage stability, the temperature and pH sensitivity of the immobilized biocatalysts and the free lipase TL were studied. Lipase immobilized on functionalized GO demonstrates superior enzymatic loading and relative activity compared to GO, with a maximum increase of 70% and 47%, respectively. The relative activity of lipase immobilized on functionalized GO was 19.21 times more than that of commercial immobilized lipase TLIM. Through molecular dynamics simulations we concluded that the increase in the relative activity of lipase TL is mainly related to its adsorption orientation and slight conformational change. Thus, our research offered a green and effective strategy to regulate the heterogeneity of nanomaterials for a suitable microenvironment to enhance the performance of immobilized lipase.

Production of low-calorie structured lipids from spent coffee grounds or olive pomace crude oils catalyzed by immobilized lipase in magnetic nanoparticles

In this study, crude oils extracted from spent coffee grounds (SCG) and olive pomace (OP) were used as raw-material to synthesize low-calorie triacylglycerols, either by acidolysis with capric acid, or by interesterification with ethyl caprate, in solvent-free media, catalyzed by sn-1,3 regioselective lipases. The Rhizopus oryzae lipase (ROL) was immobilized in magnetite nanoparticles (MNP–ROL) and tested as novel biocatalyst. MNP-ROL performance was compared with that of the commercial immobilized Thermomyces lanuginosus lipase (Lipozyme TL IM). For both oils, Lipozyme TL IM preferred interesterification over acidolysis. MNP-ROL catalyzed reactions were faster and acidolysis was preferred with yields of c.a. 50% new triacylglycerols after 3 h acidolysis of OP or SCG oils. MNP-ROL was very stable following the Sadana deactivation model with half-lives of 163 h and 220 h when reused in batch acidolysis and interesterification of OP oil, respectively.

Screening of lipases for production of novel structured lipids from single cell oils

Lipids enriched in polyunsaturated fatty acids are very susceptible to oxidation, causing the formation of potentially harmful oxidized products. Hence, it is critical to keep the temperature as low as possible during reaction and storage. In this study, five commercial immobilized lipases were evaluated for their capability to produce novel structured lipids (SLs) enriched with medium-chain fatty acids (MCFAs) through acidolysis of single cell oil (SCO) with capric acid. Among the examined lipases, NS40086 and Lipozyme RM IM showed the highest incorporation degree. The acidolysis reactions resulted in an obvious variation in the fatty acids composition as well as their positional distribution. The obtained SLs contained (33.58 %–34.09 %) capric acid at sn-1, 3 positions with increasing the content of arachidonic acid at the sn-2 position up to (49.82 %–50.25 %). The NS40086 lipase displayed 1, 3 regiospecificity towards the TAG of SCO. The acidolysis reactions using NS40086 lipase resulted in a generation of 23 TAG molecular species containing capric acid. Moreover, the NS40086 lipase was more active than Lipozyme RM IM at relatively low temperatures (35 °C and 40 °C), which could be used effectively as a promising biocatalyst in lipid synthesis.

Enzymatic synthesis of neopentyl glycol-bases biolubricants using biodiesel from soybean and castor bean as raw materials

Synthetic oleochemical esters represents a growing alternative for mineral oil-based lubricants. In this sense, the present study shows the results of enzymatic synthesis of neopentyl glycol-bases biolubricants using biodiesel from soybean and castor bean as raw materials. The potential of two commercial immobilized lipases, lipase B from Candida antarctica (Novozyme 435) and lipase from Rhizomucor miehei (Lipozyme RM IM), to produce NPG esters in a solvent-free medium was evaluated. High conversions (>95%) were obtained for both raw materials, with both enzymes, but in a shorter reaction time for soybean biodiesel (24 h) than castor biodiesel (48 h). Both enzymes could be successfully reused for six reactions, Novozyme 435 maintained ≥70% of the initial conversion using the two raw materials and Lipozyme RM IM maintained ≥90% of the first reaction conversion using castor biodiesel. The soybean NPG esters showed good viscosity index, higher than 198, and the castor NPG esters showed good pour point, lower than −20 °C, and good oxidative stability, higher than 30 min. The physico-chemical properties of the biolubricants were dependent on the biodiesel source which directly influence the final application of the products.

Highly active enzyme–metal nanohybrids synthesized in protein–polymer conjugates

Building a bridge between enzymatic and heterogeneous catalysis provides new cascade industrial processes for manufacturing. However, the reaction conditions of enzymatic and heterogeneous catalysis mutually cause deactivation of catalysts. Here, we overcame this challenge by developing a special protocol for the synthesis of hybrid catalysts. We utilized protein–polymer nanoconjugates as confined nanoreactors for the in situ synthesis of lipase–palladium (Pd) nanohybrids. The 0.8 nm Pd nanoparticles exhibited increased activity in racemization of (S)-1-phenylethylamine. At 55 °C, which matches the optimum temperature of lipase, the activity is more than 50 times that of commercial Pd/C. It was found that the Pd–O coordination in Pd subnanoclusters contributed to the high activity. In the dynamic kinetic resolutions of pharmaceutical intermediates (±)-1-phenylethylamine, (±)-1-aminoindan and (±)-1,2,3,4-tetrahydro-1-naphthylamine, the lipase–Pd nanohybrids displayed 7.6, 3.1 and 5.0 times higher efficiencies than the combination of commercial immobilized lipase Novozym 435 and Pd/C. The lipase–Pd nanohybrids can be reused without agglomeration and activity loss. Combining enzymatic and heterogeneous catalysts is challenging due to different reaction requirements. Here, a method is presented constructing single protein–polymer nanoconjugates as nanoreactors for the in situ synthesis of enzyme–metal nanohybrids with high activity at ambient conditions.

Ultrasound–assisted enzymatic biodiesel production using blended feedstock of non–edible oils: Kinetic analysis

The present study reports ultrasound–assisted biodiesel synthesis using blended feedstock of non–edible oils and commercial immobilized lipase from Thermomyces lanuginosus. Optimum process parameters obtained using Box–Behnken statistical design were as follows: alcohol/oil molar ratio = 7.64:1, enzyme loading = 3.55% (w/w) and temperature = 36 °C, conversion = 90%. Sonication of reaction mixture resulted in lowering of activation energy to 100.4 kJ/mol (from 124.4 kJ/mol under mechanical agitation). Addition of water to reaction mixture (10% v/v) not only boosted biodiesel yield from 90% to 94% but also lowered activation energy to 78.7 kJ/mol. Analysis of reaction kinetics using ordered Bi–Bi model revealed drastic rise (∼1.6×) in reaction velocity with concurrent changes in Michaelis–Menten and dissociation constant of both substrate and products. Finally, the recycled enzyme showed good retention of activity up to 6 cycles in presence of ultrasound, which further enhanced with water addition to reaction mixture.