Synthesis of ethyl ferulate in organic medium using celite-immobilized lipase

Enzymatic synthesis of pyridine heterocyclic compounds and their thermal stability

An efficient method was discovered for catalyzing the esterification under air using Novozym 435 to obtain pyridine esters. The following conditions were found to be optimal: 60 mg of Novozyme 435, 5.0 mL of n-hexane, a molar ratio of 2:1 for nicotinic acids (0.4 mmol) to alcohols (0.2 mmol), 0.25 g of molecular sieve 3A, a revolution speed of 150 rpm, a reaction temperature of 50 °C, and reaction time of 48 h. Under nine cycles of Novozym 435, the 80 % yield was consistently obtained. Optimum conditions were used to synthesize 23 pyridine esters, including five novel compounds. Among them, gas chromatography-mass spectrometry-olfactometry (GC-MS-O) showed phenethyl nicotinate (3g), (E)-hex-4-en-1-yl nicotinate (3m), and octyl nicotinate (3n) possessed strong aromas. Thermogravimetric analysis (TG) revealed that the compounds 3g, 3m and 3n exhibited stability at the specified temperature. This finding provides theoretical support for adding pyridine esters fragrance to high-temperature processed food.

Enzymatic molecular modification of water-soluble polyphenols: Synthesis, structure, bioactivity and application

The poor lipophilicity and instability of water-soluble polyphenols limit their bioavailability and application in food. However, increasing attention has been given to water-soluble polyphenols due to their multiple biological activities, which prompts the modification of the structure of water-soluble polyphenols to improve their lipophilicity and stability and enable more efficient application. This review presents the enzymatic biosynthesis of lipophilic derivatives of water-soluble polyphenols, which will change the molecular structure of water-soluble polyphenols based on the loss of hydroxyl or carboxyl groups. Therefore, the effects of reaction factors on the structure of polyphenol derivatives and the change in their bioactivities will be further analyzed. Previous studies have shown that lipases, solvent systems, and hydrophobic groups are major factors influencing the synthesis and lipophilicity of polyphenol derivatives. Moreover, the biological activities of polyphenol derivatives were changed to a certain extent, such as through the enhancement or weakening of antioxidant activity in different systems and the increase in anti-influenza virus activity and antibacterial activity. The improvement of lipophilicity also expands polyphenol application in food. This review may contribute to the efficient synthesis of lipophilic derivatives of water-soluble polyphenols to extend the utilization and application range of polyphenols.

Sustainable biosynthetic pathways to value-added bioproducts from hydroxycinnamic acids

The biorefinery concept, in which biomass is utilized for the production of fuels and chemicals, emerges as an eco-friendly, cost-effective, and renewable alternative to petrochemical-based production. The hydroxycinnamic acid fraction of lignocellulosic biomass represents an untapped source of aromatic molecules that can be converted to numerous high-value products with industrial applications, including in the flavor and fragrance sector and pharmaceuticals. This review describes several biochemical pathways useful in the development of a biorefinery concept based on the biocatalytic conversion of the hydroxycinnamic acids ferulic, caffeic, and p-coumaric acid into high-value molecules. KEY POINTS: • The phenylpropanoids bioconversion pathways in the context of biorefineries • Description of pathways from hydroxycinnamic acids to high-value compounds • Metabolic engineering and synthetic biology advance hydroxycinnamic acid-based biorefineries.

Nanostructured supports for multienzyme co-immobilization for biotechnological applications: Achievements, challenges and prospects

The synergistic combination of current biotechnological and nanotechnological research has turned to multienzyme co-immobilization as a promising concept to design biocatalysis engineering. It has also intensified the development and deployment of multipurpose biocatalysts, for instance, multienzyme co-immobilized constructs, via biocatalysis/protein engineering to scale-up and fulfil the ever-increasing industrial demands. Considering the characteristic features of both the loaded multienzymes and nanostructure carriers, i.e., selectivity, specificity, stability, resistivity, induce activity, reaction efficacy, multi-usability, high catalytic turnover, optimal yield, ease in recovery, and cost-effectiveness, multienzyme-based green biocatalysts have become a powerful norm in biocatalysis/protein engineering sectors. In this context, the current state-of-the-art in enzyme engineering with a synergistic combination of nanotechnology, at large, and nanomaterials, in particular, are significantly contributing and providing robust tools to engineer and/or tailor enzymes to fulfil the growing catalytic and contemporary industrial needs. Considering the above critics and unique structural, physicochemical, and functional attributes, herein, we spotlight important aspects spanning across prospective nano-carriers for multienzyme co-immobilization. Further, this work comprehensively discuss the current advances in deploying multienzyme-based cascade reactions in numerous sectors, including environmental remediation and protection, drug delivery systems (DDS), biofuel cells development and energy production, bio-electroanalytical devices (biosensors), therapeutical, nutraceutical, cosmeceutical, and pharmaceutical oriented applications. In conclusion, the continuous developments in nano-assembling the multienzyme loaded co-immobilized nanostructure carriers would be a unique way that could act as a core of modern biotechnological research.

An overview on the conversion of glycerol to value-added industrial products via chemical and biochemical routes

Glycerol is a common by-product of industrial biodiesel syntheses. Due to its properties, availability, and versatility, residual glycerol can be used as a raw material in the production of high value-added industrial inputs and outputs. In particular, products like hydrogen, propylene glycol, acrolein, epichlorohydrin, dioxalane and dioxane, glycerol carbonate, n-butanol, citric acid, ethanol, butanol, propionic acid, (mono-, di-, and triacylglycerols), cynamoil esters, glycerol acetate, benzoic acid, and other applications. In this context, the present study presents a critical evaluation of the innovative technologies based on the use of residual glycerol in different industries, including the pharmaceutical, textile, food, cosmetic, and energy sectors. Chemical and biochemical catalysts in the transformation of residual glycerol are explored, along with the factors to be considered regarding the choice of catalyst route used in the conversion process, aiming at improving the production of these industrial products.

Enzymatic lipophilization of bioactive compounds with high antioxidant activity: a review

Food products contain bioactive compounds such as phenolic and polyphenolic compounds and vitamins, resulting in a myriad of biological characteristics such as antimicrobial, anticarcinogenic, and antioxidant activities. However, their application is often restricted because of their relatively low solubility and stability in emulsions and oil-based products. Therefore, chemical, enzymatic, or chemoenzymatic lipophilization of these compounds can be achieved by grafting a non-polar moiety onto their polar structures. Among different methods, enzymatic modification is considered environmentally friendly and may require only minor downstream processing and purification steps. In recent years, different systems have been suggested to design the synthetic reaction of these novel products. This review presents the new trends in this area by summarizing the essential enzymatic modifications in the last decade that led to the synthesis of bioactive compounds with attractive antioxidative properties for the food industry by emphasizing on optimization of the reaction conditions to maximize the production yields. Lastly, recent developments regarding characterization, potential applications, emerging research areas, and needs are highlighted.

Ferulic Acid From Plant Biomass: A Phytochemical With Promising Antiviral Properties

Plant biomass is a magnificent renewable resource for phytochemicals that carry bioactive properties. Ferulic acid (FA) is a hydroxycinnamic acid that is found widespread in plant cell walls, mainly esterified to polysaccharides. It is well known of its strong antioxidant activity, together with numerous properties, such as antimicrobial, anti-inflammatory and neuroprotective effects. This review article provides insights into the potential for valorization of FA as a potent antiviral agent. Its pharmacokinetic properties (absorption, metabolism, distribution and excretion) and the proposed mechanisms that are purported to provide antiviral activity are presented. Novel strategies on extraction and derivatization routes, for enhancing even further the antiviral activity of FA and potentially favor its metabolism, distribution and residence time in the human body, are discussed. These routes may lead to novel high-added value biorefinery pathways to utilize plant biomass toward the production of nutraceuticals as functional foods with attractive bioactive properties, such as enhancing immunity toward viral infections.

Growth performance, carcass traits, muscle fiber characteristics and skeletal muscle mRNA abundance in hair lambs supplemented with ferulic acid

Ferulic acid (FA) is a phytochemical with various bioactive properties. It has recently been proposed that due to its phytogenic action it can be used as an alternative growth promoter additive to synthetic compounds. The objective of the present study was to evaluate the growth performance, carcass traits, fiber characterization and skeletal muscle gene expression on hair-lambs supplemented with two doses of FA. Thirty-two male lambs (n = 8 per treatment) were individually housed during a 32 d feeding trial to evaluate the effect of FA (300 and 600 mg d⁻¹) or zilpaterol hydrochloride (ZH; 6 mg d⁻¹) on growth performance, and then slaughtered to evaluate the effects on carcass traits, and muscle fibers morphometry from Longissimus thoracis (LT) and mRNA abundance of β₂-adrenergic receptor (β₂-AR), MHC-I, MHC-IIX and IGF-I genes. FA increased final weight and average daily gain with respect to non-supplemented animals (p < 0.05). The ZH supplementation increased LT muscle area, with respect to FA doses and control (p < 0.05). Cross-sectional area (CSA) of oxidative fibers was larger with FA doses and ZH (p < 0.05). Feeding ZH increased mRNA abundance for β₂-AR compared to FA and control (p < 0.05), and expression of MHC-I was affected by FA doses and ZH (p < 0.05). Overall, FA supplementation of male hair lambs enhanced productive variables due to skeletal muscle hypertrophy caused by MHC-I up-regulation. Results suggest that FA has the potential like a growth promoter in lambs.

Production and Characterization of Cross-Linked Aggregates of Geobacillus thermoleovorans CCR11 Thermoalkaliphilic Recombinant Lipase

Immobilization of enzymes has many advantages for their application in biotechnological processes. In particular, the cross-linked enzyme aggregates (CLEAs) allow the production of solid biocatalysts with a high enzymatic loading and the advantage of obtaining derivatives with high stability at low cost. The purpose of this study was to produce cross-linked enzymatic aggregates (CLEAs) of LipMatCCR11, a 43 kDa recombinant solvent-tolerant thermoalkaliphilic lipase from Geobacillus thermoleovorans CCR11. LipMatCCR11-CLEAs were prepared using (NH4)2SO4 (40% w/v) as precipitant agent and glutaraldehyde (40 mM) as cross-linker, at pH 9, 20 °C. A U10(56) uniform design was used to optimize CLEA production, varying protein concentration, ammonium sulfate %, pH, glutaraldehyde concentration, temperature, and incubation time. The synthesized CLEAs were also analyzed using scanning electron microscopy (SEM) that showed individual particles of <1 µm grouped to form a superstructure. The cross-linked aggregates showed a maximum mass activity of 7750 U/g at 40 °C and pH 8 and retained more than 20% activity at 100 °C. Greater thermostability, resistance to alkaline conditions and the presence of organic solvents, and better durability during storage were observed for LipMatCCR11-CLEAs in comparison with the soluble enzyme. LipMatCCR11-CLEAs presented good reusability by conserving 40% of their initial activity after 9 cycles of reuse.

A Simple and Efficient Method for Synthesis and Extraction of Ethyl Ferulate from γ-Oryzanol

Ethyl ferulate (EF) is a ferulic acid (FA) derivative with high commercial value. It is not found naturally and is mostly synthesized from FA via esterification with ethanol. The present work aimed to synthesize the EF from γ-oryzanol, a natural antioxidant from rice bran oil via acid-catalyzed transethylation at refluxing temperature of ethanol. The reaction was optimized by central composite design (CCD) under response surface methodology. Based on the CCD, the optimum condition for the synthesis of EF from 0.50 g of γ-oryzanol was as follows: γ-oryzanol to ethanol ratio of 0.50:2 (g/mL), 12.30% (v/v) H₂SO₄, and a reaction time of 9.37 h; these conditions correspond to a maximum EF yield of 87.11%. Moreover, the optimized transethylation condition was further validated using 12.50 g of γ-oryzanol. At the end of the reaction time, distilled water was added as antisolvent to selectively crystallize the co-products, phytosterol and unreacted γ-oryzanol, by adjusting the ethanol concentration to 49.95% (v/v). The recovery yield of 83.60% with a purity of 98% of EF was achieved. In addition, the DPPH and ABTS assays showed similar antioxidant activities between the prepared and commercial EF.

Purification and Properties of an Esterase from Bacillus licheniformis and it’s Application in Synthesis of Octyl Acetate

Background:

Esterase plays a major role in the degradation of natural materials, industrial pollutants and also provides an immense contribution to the eco-friendly approaches in various industrial applications.

Objective:

In the present study, extracellular esterase from bacterial isolate Bacillus licheniformis was purified, characterized and used in the synthesis of octyl acetate.

Methods:

Purification of esterase from Bacillus licheniformis was achieved using Sephadex G-75 column chromatography. Gas chromatography was used to analyze the octyl acetate synthesis.

Results:

The enzyme was salted out using ammonium sulphate precipitation and 60-70% saturation gave maximum specific activity of the enzyme during precipitation. A purification fold of 6.46 and yield of 9.69% was achieved when esterase from Bacillus licheniformis was purified using Sephadex G-75 column chromatography. Native as well as SDS-PAGE analysis gave a single band of 42 kDa. This showed that the enzyme was purified to homogeneity and it was a monomer with molecular weight of 42 kDa. Biochemical characterization of the enzyme revealed that it had optimum temperature of 45°C in 0.1 M Tris-HCl buffer of pH 8.0. On optimizing different parameters, such as molar ratio of reactants, incubation time, temperature, and amount of protein, the % yield of octyl acetate was found to be 77.3%.

Conclusion:

In this work, simple method was used to purify esterase and the enzyme was further used in producing esters/products of commercial value within a reasonably short period of 12 h with a maximum yield of 77.3%.

Magnetic Nano-Сomposites and their Industrial Applications

Magnetic nanocomposites are multi-component, nanosized magnetic materials, to generate the response to an external stimulus (i.e., outer inert or alternative magnetic field). The novel nanocomposites is a combination of excess of various materials such as liquid crystals, silica, gels, renewable polymers, carbon along with different magnetic particles. They have immense applications in the field of medical diagnosis and therapy, catalysis and separation. These nanocarriers are mainly classified into nanotubes, nanosheets, spherical nanoparticles, nanofibres, highly porous nanocomposites. The porous nanostructures provides a better surface for the entrapment or covalent binding of enzymes, proteins, biomolecules and drugs but the major challenge is to design and synthesize a desired structure with suitable surface properties and biocompatibility. Extensive attempts have been made to manipulate the mesoporous materials and its combination with other structure in order to synthesize a matrix with appropriate pore size, large surface area to volume ratio. “Bottom-up” and “Bottom-down” chemical-based synthesis methods have been widely employed to prepare magnetic nanoparticles. Magnetic nanocomposites are synthesized from magnetic nanoparticles and biopolymers by using sol-gel technique, chemical precipitation methods and NanogenTM, a microwave plasma method. In this chapter, we described the advances and developments in the formation/synthesis of magnetic nanocomposites. This chapter will review the characteristics, properties and applications of the magnetic nanocomposites.

SnO2 hollow nanotubes: a novel and efficient support matrix for enzyme immobilization

A major challenge in the industrial use of enzymes is maintaining their stability at elevated temperatures and in harsh organic solvents. In order to address this issue, we investigated the use of nanotubes as a support material for the immobilization and stabilization of enzymes in this work. SnO₂ hollow nanotubes with a high surface area were synthesized by electrospinning the SnCl₂ precursor and polyvinylpyrrolidone (dissolved in dimethyl formamide and ethanol). The electrospun product was used for the covalent immobilization of enzymes such as lipase, horseradish peroxidase, and glucose oxidase. The use of SnO₂ hollow nanotubes as a support was promising for all immobilized enzymes, with lipase having the highest protein loading value of 217 mg/g, immobilization yield of 93%, and immobilization efficiency of 89%. The immobilized enzymes were fully characterized by various analytical methods. The covalently bonded lipase showed a half-life value of 4.5 h at 70 °C and retained ~91% of its original activity even after 10 repetitive cycles of use. Thus, the SnO₂ hollow nanotubes with their high surface area are promising as a support material for the immobilization of enzymes, leading to improved thermal stability and a higher residual activity of the immobilized enzyme under harsh solvent conditions, as compared to the free enzyme.

Co-Immobilization of Enzymes and Magnetic Nanoparticles by Metal-Nucleotide Hydrogelnanofibers for Improving Stability and Recycling

In this paper we report a facile method for preparing co-immobilized enzyme and magnetic nanoparticles (MNPs) using metal coordinated hydrogel nanofibers. Candida rugosa lipase (CRL) was selected as guest protein. For good aqueous dispersity, low price and other unique properties, citric acid-modified magnetic iron oxide nanoparticles (CA-Fe₃O₄ NPs) have been widely used for immobilizing enzymes. As a result, the relative activity of CA-Fe₃O₄@Zn/AMP nanofiber-immobilized CRL increased by 8-fold at pH 10.0 and nearly 1-fold in a 50 °C water bath after 30 min, compared to free CRL. Moreover, the immobilized CRL had excellent long-term storage stability (nearly 80% releative activity after storage for 13 days). This work indicated that metal-nucleotide nanofibers could efficiently co-immobilize enzymes and MNPs simultaneously, and improve the stability of biocatalysts.

Ascorbyl palmitate synthesis in an organic solvent system using a Celite-immobilized commercial lipase (Lipolase 100L)

Ascorbyl palmitate was synthesized using a Celite-immobilized commercial lipase (Lipolase 100L) in dimethylsulfoxide (DMSO) as an organic solvent system. Lipase immobilized by surface adsorption onto Celite 545 matrix and subsequently exposed to 1 % glutaraldehyde showed 75 % binding of protein. The Celite-bound lipase was optimally active at 75 °C and pH 8.5 under shaking and showed maximum hydrolytic activity toward p-NPP as a substrate. The bound lipase was found to be stimulated only in the presence of Al³⁺ and EDTA. All surfactants (Tween-20, Tween-80 and Triton X-100) had an inhibitory effect on lipase activity. The optimization of various reaction conditions of ascorbyl palmitate was achieved considering one factor at a time. The esterification of ascorbic acid and palmitic acid was carried out with 1 M ascorbic acid and 2.5 M palmitic acid in DMSO at 75 °C for 18 h under shaking (120 rpm). Molecular sieves had an important effect on the ester synthesis resulting in an enhanced yield. The by-product (H₂O) produced in the reaction was scavenged by the molecular sieves (20 mg/ml) added in the reaction mixture which enhanced the ester yield to 80 %. The characterization of synthesized ester was done through FTIR spectroscopy.

Lipase catalysis in organic solvents: advantages and applications

Lipases are industrial biocatalysts, which are involved in several novel reactions, occurring in aqueous medium as well as non-aqueous medium. Furthermore, they are well-known for their remarkable ability to carry out a wide variety of chemo-, regio- and enantio-selective transformations. Lipases have been gained attention worldwide by organic chemists due to their general ease of handling, broad substrate tolerance, high stability towards temperatures and solvents and convenient commercial availability. Most of the synthetic reactions on industrial scale are carried out in organic solvents because of the easy solubility of non-polar compounds. The effect of organic system on their stability and activity may determine the biocatalysis pace. Because of worldwide use of lipases, there is a need to understand the mechanisms behind the lipase-catalyzed reactions in organic solvents. The unique interfacial activation of lipases has always fascinated enzymologists and recently, biophysicists and crystallographers have made progress in understanding the structure-function relationships of these enzymes. The present review describes the advantages of lipase-catalyzed reactions in organic solvents and various effects of organic solvents on their activity.

Ultrasound assisted synthesis of methyl butyrate using heterogeneous catalyst

Ultrasound assisted esterification of butyric acid with methanol was investigated in an ultrasound irradiated isothermal batch reactor using acid ion-exchange resin (amberlyst-15) as a catalyst. Effect of parameters such as temperature (323-353 K), catalyst loading (0-8.5%w/w), alcohol to acid ratio, M (2-6), ultrasound power (0-145 W), duty cycle (0-85%) and amount of molecular sieves added (0-11%w/w) on the rate of reaction was studied. At optimized parameters, a maximum conversion of 91.64% was obtained in 120 min in presence of ultrasound. Experimental kinetic data were correlated by using Eley-Rideal (ER) and Langmuir-Hinshelwood-Hougen-Watson (LHH W) models taking into account reverse reaction. Studies showed that single site LHHW with reactants and products both adsorbing on catalyst surface was most suited for the obtained experimental data. Activation energy determined based on heterogeneous kinetics was in the range 49.31-57.54 kJ/mol while it was 18.29 kJ/mol using homogeneous model.

Alkyl caffeates improve the antioxidant activity, antitumor property and oxidation stability of edible oil

Caffeic acid (CA) is distributed widely in nature and possesses strong antioxidant activity. However, CA has lower solubility in non-polar media, which limits its application in fat-soluble food. To increase the lipophilicity of natural antioxidant CA, a series of alkyl caffeates were synthesized and their antioxidant and antitumor activities were investigated. The antioxidant parameters, including the induction period, acid value and unsaturated fatty acid content, of the alkyl caffeates in edible oil were firstly investigated. The results indicated that alkyl caffeates had a lower DPPH IC₅₀ (14–23 µM) compared to CA, dibutyl hydroxy toluene (BHT) and Vitamin C (24–51 µM), and significantly inhibited four human cancer cells (SW620, SW480, SGC7901 and HepG2) with inhibition ratio of 71.4–78.0% by a MTT assay. With regard to the induction period and acid value assays, methyl and butyl caffeates had higher abilities than BHT to restrain the oxidation process and improve the stability of edible oil. The addition of ethyl caffeate to oil allowed maintenance of a higher unsaturated fatty acid methyl ester content (68.53%) at high temperatures. Overall, the alkyl caffeats with short chain length (n<5) assessed better oxidative stability than those with long chain length. To date, this is the first report to the correlations among the antioxidant activity, anticancer activity and oxidative stability of alkyl caffeates.

Organic solvent tolerant lipases and applications

Lipases are a group of enzymes naturally endowed with the property of performing reactions in aqueous as well as organic solvents. The esterification reactions using lipase(s) could be performed in water-restricted organic media as organic solvent(s) not only improve(s) the solubility of substrate and reactant in reaction mixture but also permit(s) the reaction in the reverse direction, and often it is easy to recover the product in organic phase in two-phase equilibrium systems. The use of organic solvent tolerant lipase in organic media has exhibited many advantages: increased activity and stability, regiospecificity and stereoselectivity, higher solubility of substrate, ease of products recovery, and ability to shift the reaction equilibrium toward synthetic direction. Therefore the search for organic solvent tolerant enzymes has been an extensive area of research. A variety of fatty acid esters are now being produced commercially using immobilized lipase in nonaqueous solvents. This review describes the organic tolerance and industrial application of lipases. The main emphasis is to study the nature of organic solvent tolerant lipases. Also, the potential industrial applications that make lipases the biocatalysts of choice for the present and future have been presented.

A novel chemoenzymatic synthesis of propyl caffeate using lipase-catalyzed transesterification in ionic liquid

Propyl caffeate has the highest antioxidant capacity in the caffeate alkyl esters family, but industrial production of propyl caffeate is hindered by low yields using either the chemical or enzymatic catalysis method. To set up a high-yield process for obtaining propyl caffeate, a novel chemoenzymatic synthesis method using lipase-catalyzed transesterification of an intermediate methyl caffeate or ethyl caffeate and 1-propanol in ionic liquid was established. The maximum propyl caffeate yield of 98.5% was obtained using lipase-catalyzed transesterification under the following optimal conditions: Novozym 435 as a biocatalyst, [Bmim][CF3SO3] as a medium, a molar ratio of methyl caffeate to 1-propanol of 1:5, a mass ratio of methyl caffeate to lipase of 1:20, and a reaction temperature of 60°C. The two-step conversion of caffeic acid to propyl caffeate via methyl caffeate is an efficient way to prepare propyl caffeate with an overall yield of 82.7%.

Synthesis of isopropyl ferulate using silica-immobilized lipase in an organic medium

Immobilization of lipases has proved to be a useful technique for improving an enzyme's activity in organic solvents. In the present study, the performance of a silica-immobilized lipase was evaluated for the synthesis of isopropyl ferulate in DMSO. The biocatalyst was cross-linked onto the matrix with 1% glutaraldehyde. The effects of various parameters, molar ratio of ferulic acid to isopropyl alcohol (25 mM : 100 mM), concentration of biocatalyst (2.5–20 mg/mL), molecular sieves (25–250 mg/mL), and various salt ions, were studied consecutively as a function of percent esterification. Immobilized lipase at 25 mg/mL showed maximum esterification (~84%) of ferulic acid and isopropanol at a molar ratio of 25 mM : 100 mM, respectively, in DMSO at 45°C in 3 h under shaking (150 rpm). To overcome the inhibitory effect of water (a byproduct) if any, in the reaction mixture, molecular sieves (3 Å × 1.5 mm; 100 mg/mL) were added to the reaction mixture to promote the forward reaction. Salt ions like Ca²⁺, Cd²⁺, and Fe²⁺ enhanced the activity of immobilized biocatalyst while a few ions like Co²⁺, Zn²⁺, Mg²⁺, Mn²⁺, Al³⁺, and Na⁺ had mild inhibitory effect. Approximately, one third of total decrease in the esterification efficacy was observed after the 5th repetitive cycle of esterification.