Miehei Lipase Research Articles

Enzymatic Transesterification Using Different Immobilized Lipases and its Biodiesel Effect on Gas Emission

Biodiesel, a third-generation bio-fuels, offering several advantages over regular diesel fuel. Waste cooking oil (WCO) emerges as an ideal feedstock due to its availability and easy accessibility. In this work, biodiesel is utilized from two different types of immobilized lipases: Rhizomucor miehei lipase (RMIM) and Candida antarctica lipase B (CALB). The impact of the molar ratio of oil to methyl acetate (1:3-1:12) was evaluated for both lipases, and the resultant biodiesel was tested in diesel engine. The enzymatic transesterification was carried out in ultrasonic assistance and the results showed that the greatest yield of 81.20% at 45℃, using CALB as a biocatalyst, 1.8% (w/v) lipase and oil to methyl acetate molar ratio of 1:12 within 3 hours. Triacetin, by-product was determined their concentration for each molar ratio and analyzed using FTIR range of 500cm-1 to 4000cm-1, revealing a significant absorption peak at 1238.90cm-1. Biodiesel was blended with commercial diesel fuel in varying quantities of 7, 10, and 20% by volume (B20). The results were compared to Industrial Diesel Fuel 7% (B7) and Commercial Diesel Fuel 10% (B10). NOx and CO2 emission drops as the percentage of diesel/biodiesel blends increases, supporting WCO as a cost-effective biodiesel feedstock with low petrol pollution.

A Whole-Process Visible Strategy for the Preparation of Rhizomucor miehei Lipase with Escherichia coli Secretion Expression System and the Immobilization.

Rhizomucor miehei (RM) lipase is a regioselective lipase widely used in food, pharmaceutical and biofuel industries. However, the high cost and low purity of the commercial RM lipase limit its industrial applications. Therefore, it is necessary to develop cost-effective strategies for large-scale preparation of this lipase. The present study explored the high-level expression of RM lipase using superfolder green fluorescent protein (sfGFP)-mediated Escherichia coli secretion system. The sfGFP(-15) mutant was fused to the C-terminus of RM lipase to mediate its secretion expression. The yield of the fusion protein reached approximately 5.1g/L with high-density fermentation in 5-L fermentors. Unlike conventional secretion expression methods, only a small portion of the target protein was secreted into the cell culture while majority of the fusion protein was still remained in the cytoplasm. However, in contrast to intracellular expression, the target protein in the cytoplasm could be transported efficiently to the supernatant through a simple washing step with equal volume of phosphate saline (PBS), without causing cell disruption. Hence, the approach facilitated the downstream purification step of the recombinant RM lipase. Moreover, contamination or decline of the engineered strain and degradation or deactivation of the target enzyme can be detected efficiently because they exhibited bright green fluorescence. Next, the target protein was immobilized with anion-exchange and macropore resins. Diethylaminoethyl sepharose(DEAE), a weak-basic anion-exchange resin, exhibited the highest bind capacity but inhibited the activity of RM lipase dramatically. On the contrary, RM lipase fixed with macropore resin D101 demonstrated the highest specific activity. Although immobilization with D101 didn't improve the activity of the enzyme, the thermostability of the immobilized enzyme elevated significantly. The immobilized RM lipase retained approximately 90% of its activity after 3-h incubation at 80°C. Therefore, D101 was chosen as the supporting material of the target protein. The present study established a highly efficient strategy for large-scale preparation of RM lipase. This innovative technique not only provides high-purity RM lipase at a low cost but also has great potential as a platform for the preparation of lipases in the future.

Deciphering the immobilization of lipases on hydrophobic wrinkled silica nanoparticles

In this work, the adsorption of Candida antarctica B (CALB) and Rhizomucor miehei (RML) lipases into hydrophobic wrinkled silica nanoparticles (WSNs) is investigated. WSNs are hydrophobized by chemical vapor deposition. Both proteins are homogeneously distributed inside the pores of the nanoparticles, as confirmed by Transmission Electron Microscopy and Energy Dispersive X-ray measurements. The maximum enzyme load of CALB is twice that obtained for RML. Fourier Transform Infrared Spectroscopy confirms the preservation of the enzyme secondary structure after immobilization for both enzymes. Adsorption isotherms fit to a Langmuir model, resulting in a binding constant (KL) for RML 4.5-fold higher than that for CALB, indicating stronger binding for the former. Kinetic analysis reveals a positive correlation between enzyme load and RML activity unlike CALB where activity decreases along the enzyme load increases. Immobilization allows for enhancing the thermal stability of both lipases. Finally, CALB outperforms RML in the hydrolysis of ethyl-3-hydroxybutyrate. However, immobilized CALB yielded 20 % less 3-HBA than free lipase, while immobilized RML increases 3-fold the 3-HBA yield when compared with the free enzyme. The improved performance of immobilized RML can be explained due to the interfacial hyperactivation undergone by this lipase when immobilized on the superhydrophobic surface of WSNs.

Lipase in-situ immobilized in covalent organic framework: Enzymatic properties and application in the preparation of 1, 3-dioleoyl-2-palmitoylglycerol

In this study, the critical importance of designing an appropriate immobilized carrier and method for free lipase to ensure exceptional biological catalytic activity and stability was emphasized. Covalent organic frameworks (COF-1) were synthesized as a novel porous carrier with an azine structure (-CN-NC-) through the condensation of hydrazine hydrate and benzene-1,3,5-tricarbaldehyde at room temperature. Simultaneously, Rhizomucor miehei lipase (RML) was immobilized within the COF-1 carrier using an in-situ aqueous phase method. Characterization of the carrier and RML@COF-1 and evaluation of the lipase properties of RML and RML@COF-1 through p-Nitrophenyl palmitate hydrolysis were conducted. Additionally, application in the synthesis of 1, 3-dioleoyl-2-palmitoylglycerol (OPO) was explored. The results showed that RML@COF-1 exhibited a high enzymatic loading of 285.4 mg/g. Under 60℃ conditions, the activity of RML@COF-1 was 2.31 times higher than that of free RML, and RML@COF-1 retained 77.25% of its original activity after 10 cycles of repeated use, indicating its excellent thermal stability and repeatability. Under the optimal conditions (10%, 1:8 PPP/OA, 45℃, 5 h), the yield of OPO reached 47.35%, showcasing the promising application prospects of the novel immobilized enzyme synthesized via in-situ aqueous phase synthesis for OPO preparation.

New Forms of Neuroactive Phospholipids for DHA Enrichment in Brain.

Low levels of docosahexaenoic acid (DHA) in the brain have been related to neurological disorders, like Alzheimer's disease (AD). After ingestion, dietary DHA must cross the blood-brain barrier, where it is absorbed as lysophosphatidylcholine (LPC), due to its role as a preferential DHA carrier in the brain. This work aimed at the production of LPC-DHA extracts to be used in supplementation/food fortification intended neural enrichment in DHA. As it is rich in DHA, especially its phospholipids (PL), Atlantic mackerel (Scomber scombrus, caught in Spring/2022) was used as a raw material. The polar lipids fraction was separated and hydrolysed with Rhizomucor miehei lipase, to enzymatically convert phosphatidylcholine (PC) into LPC. The fish (muscle and by-products) lipids fraction was used for total lipids (TL) content, lipid classes (LC) and fatty acid (FA) profile evaluation, whilst polar lipids extracts were studied for LC production and FA analysis. Muscle TL ranged between 1.45 and 4.64 g/100 g (WW), while by-products accounted for 7.56-8.96 g/100 g, with the highest contents being found in March. However, PL were more abundant in muscle (22.46-32.20% of TL). For polar lipids extracts, PL represented 50.79% of TL, among which PC corresponded to 57.76% and phosphatidylethanolamine to 42.24%. After hydrolysis, nearly half of this PC was converted into LPC. When compared to the initial PC, DHA relative content (33.6% of total FA) was significantly higher after hydrolysis: 55.6% in PC and 73.6% in LPC. Such extract, obtained from this undervalued species, may represent a promising strategy to increase DHA uptake into brain cells while allowing this species to upgrade.

Combined cross-linking of Rhizomucor miehei lipase and Candida antarctica lipase B for the effective enrichment of omega-3 fatty acids in fish oil

The incorporation of a non-specific lipase and a sn-1,3 specific one in a single immobilized system can be a promising approach for the exploitation of both lipases. A one-step immobilization platform mediated by an isocyanide-based multi-component reaction was applied to create co-cross-linked enzymes (co-CLEs) of lipases from Rhizomucor miehei (sn-1,3 specific) and Candida antarctica (non-specific). Glutaraldehyde was found to be effective cross-linker by producing specific activity of 16.9 U/mg and immobilization yield of 99 %. High activity recovery of up to 404 % was obtained for immobilized derivatives. Leaking experiment showed covalent nature of the cross-linking processes. BSA had considerable effect on the immobilization process, providing 87–100 % immobilization yields and up to 10 times improvement in the specific activity of the immobilized derivatives. Scanning electron microscopy images showed flower-like and rod-like structures for the CLEs prepared by glutaraldehyde and undecanedicarboxylic acid, respectively. The prepared co-CLEs were examined in non-selective enrichment of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil, showing capability of releasing up to 100 % of both omega-3 fatty acids within 8 h of the reaction. The reusability of co-CLEs in five successive cycles presented retaining 63–72 % of their initial activities after the fifth reuse cycle in the hydrolysis reaction.

Biocatalytic Insights for The Synthesis of New Potential Prodrugs: Design of two Ibuprofen Derivatives

Due to its effectiveness, ibuprofen is one of the most popular anti-inflammatory drugs worldwide. However, the poor water solubility of this active ingredient severely limits its spectrum of pharmaceutical formulations (and often results in severe adverse effects due to high administered doses). To overcome these limitations, in this work, we enzymatically synthesized more hydrophilic derivatives of ibuprofen through its covalent attachment to two biobased polyalcohols: erythritol and glycerol. Herein, we report the optimized reaction conditions to produce an IBU–erythritol ester (82% ± 4% of conversion) by using Candida antarctica lipase B (CalB). Furthermore, we also report the enantioselective solventless esterification of (S)-ibuprofen with glycerol (83% ± 5% of conversion), exploiting immobilized Rhizomucor miehei lipase as a biocatalyst. The full NMR characterizations of the prodrug esters were performed via 1H, 13C-NMR, DEPT, COSY, HSQC, and HMBC-NMR. The approach reported in this work can be extended to a large variety of poorly water-soluble active pharmaceutical ingredients (APIs).

Optimizing the First Step of the Biocatalytic Process for Green Leaf Volatiles Production: Lipase-Catalyzed Hydrolysis of Three Vegetable Oils.

Green leaf volatiles (GLVs), including short chain volatile aldehydes, are widely used in the flavor and food industries because of their fresh aroma. To meet the growing demand for natural GLVs with high added value, the use of biocatalytic processes appears as a relevant application. In such processes, vegetable oils are bioconverted into GLVs. First, the triacylglycerols of the oils are hydrolyzed by a lipase. Then, the free polyunsaturated fatty acids are converted by a lipoxygenase. Finally, volatile C6 or C9 aldehydes and 9- or 12-oxoacids are produced with a hydroperoxide lyase. Optimization of each biocatalytic step must be achieved to consider a scale-up. In this study, three oils (sunflower, hempseed, and linseed oils) and three lipases (Candida rugosa, Pseudomonas fluorescens, and Rhizomucor miehei lipases) have been tested to optimize the first step of the process. The experimental design and response surface methodology (RSM) were used to determine the optimal hydrolysis conditions for each oil. Five factors were considered, i.e., pH, temperature, reaction duration, enzyme load, and oil/aqueous ratio of the reaction mixture. Candida rugosa lipase was selected as the most efficient enzyme to achieve conversion of 96 ± 1.7%, 97.2 ± 3.8%, and 91.8 ± 3.2%, respectively, for sunflower, hempseed, and linseed oils under the defined optimized reaction conditions.

Study of volatile compounds profiles in milk matrices using Enterococcus faecalis EstA and Rhizomucor miehei lipase

The use of esterase/lipase enzymes of different origins in food industry is a widely employed strategy to enhance the formation of characteristic aromatic compounds derived from fat and diversify flavour. In the present work, we studied EstA enzyme of Enterococcus faecalis and a high purity Rhizomucor miehei lipase (Palatase). EstA was obtained recombinantly in Escherichia coli BL21 (DE3), and optimum esterase activity was detected at pH 6.75 and 40 °C. We evaluated the effect of the enzymes on milk mixtures prepared with different fat contents (2.8 and 6%) and structure (native or homogenized) on volatile compounds profiles. The milk fat structure before and after the application of low homogenization was characterized by dynamic light dispersion and microscopy. Native milk fat mixtures presented particles of 4.6 μm and 184 nm and homogenized mixtures had particles of 1.4 μm and 258 nm; microscopy images were in concordance with these results. Fifteen volatile compounds were identified, including ketones, esters, alcohols, and acids. We showed the key role of milk fat levels and microstructure in the nature of the volatile compounds produced by the R. miehei enzyme. Both in native or homogenized states, the highest content of fat favored a higher production of acids whereas the lowest fat level favored a higher esters production along with a more balanced volatile profile. For EstA enzyme, results showed a limited action on fat, as biosynthesis of esters only increased with the highest fat level homogenized.

Evaluation the selectivity of three lipases in the synthesis of 1-oleoyl-2-palmitoyl-3-linoleoylglycerol, an asymmetric triacylglycerol

1-Oleoyl-2-palmitoyl-3-linoleoylglycerol (OPL) is the most abundant triacylglycerol (TAG) molecule in Chinese human milk. The selectivity of three lipases including Rhizomucor miehei lipase (RML), Thermomyces lanuginose lipase (TL), and Candida antarctica lipase (CALB) in OPL synthesis were evaluated. The effects of different reaction conditions on selectivity were first investigated. Unexpectedly, the three sn-1,3 regioselectivity lipases, also have selectivity for the structure of product TAGs. Compared with symmetric TAGs, lipases had poor selectivity toward asymmetric OPL. Furthermore, molecular simulations were used to deeply understand the molecular factors affecting lipase selectivity. The results showed that hydrophobic interactions, lipases lid domain flexibility, and the stability of hydrogen bonds between lipases and TAGs were the main molecular factors responsible for the selectivity of lipases.

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.

Inside Out Computational Redesign of Cavities for Improving Thermostability and Catalytic Activity of Rhizomucor Miehei Lipase.

Cavities are created by hydrophobic interactions between residue side chain atoms during the folding of enzymes. Redesigning cavities can improve the thermostability and catalytic activity of the enzyme; however, the synergistic effect of cavities remains unclear. In this study, Rhizomucor miehei lipase (RML) was used as a model to explore volume fluctuation and spatial distribution changes of the internal cavities, which could reveal the roles of internal cavities in the thermostability and catalytic activity. We present an inside out cavity engineering (CE) strategy based on computational techniques to explore how changes in the volumes and spatial distribution of cavities affect the thermostability and catalytic activity of the enzyme. We obtained 12 single-point mutants, among which the melting temperatures (Tm) of 8 mutants showed an increase of more than 2°C. Sixteen multipoint mutations were further designed by spatial distribution rearrangement of internal cavities. The Tm of the most stable triple variant, with mutations including T21V (a change of T to V at position 21), S27A, and T198L (T21V/S27A/T198L), was elevated by 11.0°C, together with a 28.7-fold increase in the half-life at 65°C and a specific activity increase of 9.9-fold (up to 5,828 U mg-1), one of the highest lipase activities reported. The possible mechanism of decreased volumes and spatial rearrangement of the internal cavities improved the stability of the enzyme, optimizing the outer substrate tunnel to improve the catalytic efficiency. Overall, the inside out computational redesign of cavities method could help to deeply understand the effect of cavities on enzymatic stability and activity, which would be beneficial for protein engineering efforts to optimize natural enzymes. IMPORTANCE In the present study, R. miehei lipase, which is widely used in various industries, provides an opportunity to explore the effects of internal cavities on the thermostability and catalytic activity of enzymes. Here, we execute high hydrostatic pressure molecular dynamics (HP-MD) simulations to screen the critical internal cavity and reshape the internal cavities through site-directed mutation. We show that as the global internal cavity volume decreases, cavity rearrangement can improve the stability of the protein while optimizing the substrate channel to improve the catalytic efficiency. Our results provide significant insights into understanding the mechanism of action of the internal cavity. Our strategy is expected to be applied to other enzymes to promote increases in thermostability and catalytic activity.

Synthesis of biocatalyst in microfluidic reactor for β-sitosterol esterification

The goal of the current study is to propose and study an innovative method in synthesizing biocatalyst within a microfluidic reactor and later use it in the esterification of β-sitosterol. A droplet microreactor was specially designed and fabricated using soft-lithography technique and was used for formulation of silica nanoparticles. Sol-gel reaction method was adapted in the microreactor to produce nanoparticles which were used as the support for lipase from Rhizomucor miehei. Another microfluidics reactor was also designed and fabricated for the immobilization of the Lipase on the silica nanoparticles through a physical adsorption technique producing a biocatalyst. The catalytic efficacy of the biocatalyst was next evaluated by esterifying β-sitosterol (the main component of phytosterol) at two different catalyst loadings and comparing it to free lipase under the same experimental parameters. Samples were taken periodically and diluted with n-hexane before injecting them into gas chromatography for analysis. Spherical silica nanoparticles synthesized from the microreactor have good monodispersity with an average size of 480 nm. The silica nanoparticles produced in the microflow system showed large BET surface area, pore volume, and pore size of 125.08 m2/g, 0.42 cm3/g, and 135.70 Å, respectively. Rhizomucor miehei lipase was successfully adsorbed on the support with lipase activity around 16160 U/g. Increasing the catalyst loading increased the esterification rate from 79% to 97.3% when utilized 2.0 and 2.5 mg/ml of immobilized lipase, respectively. The findings also revealed that, under comparable reaction parameters, immobilized lipase had a higher esterification rate than free lipase.

Facile Preparation of Dopamine-Modified Magnetic Zinc Ferrite Immobilized Lipase for Highly Efficient Synthesis of OPO Functional Lipid

1,3-Dioleoyl-2-palmitoylglycerol (OPO) has been a hotspot of functional oils research in recent years, but due to the high cost of sn-1,3 specific lipase in enzymatic synthesis and the lack of biocatalyst stability, large-scale industrial application is difficult. In this study, the prepared magnetic ZnFe2O4 was functionalized with dopamine to obtain ZnFe2O4@PDA, and the nano-biocatalyst ZnFe2O4@PDA@RML was prepared by immobilizing sn-1,3 specific lipase of Rhizomucor miehei lipase (RML) via a cross-linking method. The existence of RML on ZnFe2O4@PDA was confirmed by XRD, FTIR, SEM, and TEM. This strategy proved to be simple and effective because the lipase immobilized on magnetic nanoparticles could be quickly recovered using external magnets, enabling reuse of the lipase. The activity, adaptability to a high temperature, pH value, and operational stability of immobilized RML were superior to those of free RML. After optimizing the synthesis conditions, the OPO yield was 42.78%, and the proportion of PA at the sn-2 position (PA-Sn2) was 54.63%. After the first four cycles, the activity of ZnFe2O4@PDA@RML was not significantly affected. The magnetically immobilized lipase has good thermal stability, long-term storage stability, reusability, and high catalytic activity. It can be used as a green and efficient biocatalyst to synthesize the OPO functional lipid.

Cross-linked lipase particles with improved activity; application of a non-toxic linker for cross-linking

The preparation of cross-linked enzymes is often performed through enzyme aggregation or crystallization prior to cross-linking by glutaraldehyde as the most common linker. Isocyanide-based multi-component reactions (ICMRs) provide a one-step process to prepare cross-linked preparations of enzymes directly from their soluble forms. ICMRs accept a variety of functional groups to be involved in the coupling reaction. We here introduce cysteamine as a novel non-toxic alternative for glutaraldehyde to be used as a cross-linker in cross-linking reactions implemented by ICMRs. The cross-linked enzymes (CLEs) of Rhizomucor miehei lipase (RML) and Thermomyces lanuginosa lipase (TLL) were prepared with high immobilization yields (up to 97%). The results showed the maximum activities of 43.7 U/mg and 213.35 U/mg for the immobilized derivatives of RML and TLL, respectively, presenting an 11-fold and 10-fold improvement compared to the activity of the corresponding soluble lipases. The immobilized derivatives showed improved thermal and co-solvent stability. Additionally, the CLEs of TLL showed a selectivity of 19.9 in the selective hydrolysis of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil. The used linker provides an alternative strategy for CLEs production, particularly where the traditional cross-linking method has the possible risk of reaction contamination by weakly bonded glutaraldehyde molecules.

Efficient biodiesel production from waste cooking oil by fast co-immobilization of lipases from Aspergillus oryzae and Rhizomucor miehei in magnetic chitosan microcapsules

To achieve an efficient and cost-effective conversion from waste cooking oil (WCO) to biodiesel, a facile one-pot co-immobilization of Aspergillus oryzae lipase (AOL) and Rhizomucor miehei lipase (RML) was developed by rapid encapsulation of magnetic chitosan microcapsules. The encapsulation process was accomplished by self-assembly of negatively charged magnetic nanoparticles (citrate modified Fe3O4) on ionic cross-linked chitosan-citrate aggregates containing lipases. Integrating Tween 80 bio-imprinting of lipases, the co-immobilized AOL@RML (co-im Tween 80-AOL@RML) achieved a significant increase in activity and reached 98.5 % biodiesel yield under optimal conditions, which was 1.3 and 1.6 times higher than that of single immobilized AOL and RML, respectively. Notably, owing to the beneficial synergistic impact of methanol-tolerable AOL and thermal-stable RML, co-im Tween 80-AOL@RML displayed superior activity over single lipase counterparts under excess methanol and variable temperatures. The co-im Tween 80-AOL@RML could maintained 96 % activity after 3 cycles of biodiesel production; however, showed an obvious inactivation after continued reuse. Moreover, methanol-induced denaturation of lipases and glycerol-caused agglomeration of the magnetic nanoparticles during continued transesterification were ascertained by fourier transform infrared analysis and scanning electron microscopy. This study provides new pathways for constructing multi-lipase co-immobilzation as well as an economical and effective biocatalyst for biodiesel production from WCO.

A multi-component approach for co-immobilization of lipases on silica-coated magnetic nanoparticles: improving biodiesel production from waste cooking oil.

The capability of multi-component reactions in rapid immobilization of enzymes was considered for co-immobilization of Thermomyces lanuginous lipase (TLL) and Candida antarctica lipase B (CALB) [TLL: CALB]; Rhizomucor miehei lipase (RML) and CALB [RML: CALB] on amine-functionalized silica-coated magnetic nanoparticles (Fe3O4@SiO2-NH2). Immobilization of different ratios of lipases was performed within 3h under mild conditions; producing specific activity ranging from 29 to 35 U/mg for TLL:CALB and 21-34 U/mg for RML:CALB. The co-immobilized derivatives showed improved co-solvent and thermal stability compared to the corresponding free enzymes. All the derivatives were also used to catalyze the transesterification of waste cooking oil with methanol to produce biodiesel (fatty acid methyl esters). Response surface method (RSM) and a central composite rotatable design (CCRD) were used to study the effects of different factors on the FAME yield. Fe3O4@SiO2-NH2-RML-CALB and Fe3O4@SiO2-NH2-TLL-CALB had maximum FAME yields of 99-80%, respectively.

Quality Evaluation of Plant Oil Blends Interesterified by Using Immobilized Rhizomucor miehei Lipase

The aim of this research was to evaluate the quality and oxidative stability of enzymatically interesterified plant oil blends. The model plant oil blends consisted of tomato seed oil and coconut oil, which were applied to enzymatic interesterification in the presence of a microbial lipase. To obtain quality characteristics of the enzymatically interesterified oil blends, the following analyses were performed: fatty acids composition and their distribution in internal position (sn-2) in triacylglycerols, oxidative induction time, melting profile, acid value (AV), and peroxide value (PV). The analyzed oil blends contain 6 to 25% monounsaturated fatty acids and 16 to 42% polyunsaturated fatty acids. Additionally, it was noticed that the major monounsaturated fatty acid was oleic acid, with its contribution ranging from 9 to 19%. In most cases, oleic and linoleic acids occupied the sn-2 position of the triacylglycerol molecules, with their contribution reaching 35 to 72% and 34 to 71%, respectively. The enzymatically interesterified oil mixtures were characterized by a relatively long oxidation induction time (41–87 min). Melting profiles of the tested samples revealed the presence of a diversified number of endothermic peaks. The AV and PV of the tested oil blends exceeded 10 mg KOH g−1 fat and 1 meq O2 kg−1 fat, respectively. In conclusion, the tested interesterified plant oil blends are characterized by acceptable thermal and oxidative stability and fatty acid profile.

Optimization of the Fermentative Production of Rhizomucor miehei Lipase in Aspergillus oryzae by Controlling Morphology.

Morphology plays an important role in the fermentation bioprocess of filamentous fungi. In this study, we investigated the controlling strategies of morphology that improved the efficiency of Rhizomucor miehei lipase (RML) production using a high-yield Aspergillus oryzae. First, the inoculated spore concentrations were optimized in seed culture, and the RML activity increased by 43.4% with the well-controlled mycelium pellets in both ideal sizes and concentrations. Then, the initial nitrogen source and agitation strategies were optimized to regulate the morphology of Aspergillus oryzae in a 5 L bioreactor, and the established stable fermentation system increased the RML activity to 232.0 U/mL, combined with an increase in total RML activity from 98,080 U to 487,179 U. Furthermore, the optimized fermentation strategy was verified by a high-yield Aspergillus oryzae and achieved an additional improvement of RML activity, up to 320.0 U/mL. Moreover, this optimized fermentation bioprocess was successfully scaled up to a 50 L bioreactor, and the RML activity reached 550.0 U/mL. This work has established a stable precision fermentation bioprocess for RML production by A. oryzae in bioreactors, and the controlling strategy developed in this study could potentially be extended to an industrial scale for RML production with high efficiency.

(Hydroxypropyl)methyl Cellulose-Chitosan Film as a Matrix for Lipase Immobilization-Part ΙΙ: Structural Studies.

The present work reports on the structural study of a film made of a hybrid blend of biopolymers used as an enzyme carrier. A cellulose derivative (HPMC) and chitosan (CS) were combined in order to formulate a film on which Mucor miehei lipase was immobilized. The film was successfully used as a biocatalyst; however, little is known about the structure of the system. Therefore, small-angle X-ray scattering, Fourier transform infrared spectroscopy (FTIR), optical microscopy, and scanning electron microscopy (SEM), as well as microindentation measurements, were used to shed light on the structure of the promising biocatalyst. Among the results, intermolecular hydrogen bonds were observed between the amide groups of the two polymers and the lipase. The presence of the enzyme does not seem to affect the mechanical properties of the matrix. The used film after 35 cycles of reaction seemed to be fatigued and had lost part of its humidity, explaining the reduction of the enzyme activity.