Production of diacylglycerols from glycerol monooleate and ethyl oleate through free and immobilized lipase-catalyzed consecutive reactions

The ability of free and immobilized lipase on the production of diacylglycerols (DAG) by transesterification of glycerol monooleate (GMO) and ethyl oleate was investigated. Among three free lipases such as lipase G (Penicillium cyclopium), lipase AK (Pseudomonas fluorescens) and lipase PS (Pseudomonas cepacia), lipase PS exhibited the highest DAG productivity, and the DAG content gradually increased up to 24 hours reaction and then remained steady. The comparative result for DAG productivity between free lipase PS and immobilized lipases (lipase PS-D and Lipozyme RM IM) during nine times of 24 hours reaction indicated that total DAG production was higher in immobilized lipase PS-D (183.5mM) and Lipozyme RM IM (309.5mM) than free lipase PS (122.0mM) at the first reaction, and that the DAG production rate was reduced by consecutive reactions, in which more sn-1,3-DAG was synthesized than sn-1,2-DAG. During the consecutive reactions, the activity of lipase PS was relatively steady by showing similar DAG content, whereas DAG production of lipase PS-D and Lipozyme RM IM was gradually decreased to 69.9 and 167.1mM at 9th reaction, respectively, resulting in 62% and 46% reduced production when compared with 1st reaction. Interestingly, from 7th reaction lipase PS produced more DAG than immobilized lipase PS-D, and exhibited a stable activity for DAG production. Therefore, the present study suggested that DAG productivity between GMO and ethyl oleate was higher in immobilized lipases than free lipases, but the activity was reduced with repeated uses.     

FTIR-ATR characterization of free Rhizomucor meihei lipase (RML), Lipozyme RM IM and chitosan-immobilized RML

The synthesis and characterization of biocatalysts based on lipase from Rhizomucor miehei (RML) immobilized on chitosan-based supports were investigated. The enzyme was immobilized on chitosan following two strategies: (i) physical adsorption; and (ii) covalent bonding using glutaraldehyde. The content of enzyme bound in the supports, as precipitable protein, was analyzed using UV/visible methods. FTIR-ATR spectroscopy was employed to characterize the prepared biocatalysts, as well the native enzyme and a commercial biocatalyst Lipozyme RM IM, used as reference materials. Analysis of the amide I′ signal allowed to follow the changes in the secondary structure of the enzyme after binding to the support and its thermal stability. The hydrolysis of ethyl stearate monitored in situ by FTIR-ATR was used as a test reaction. Results showed that RML was bound to Chit and Glut–Chit with minor changes in its secondary structure, thermal stability and enzymatic activity in a selected reaction test.     

Resolution of racemic ketoprofen in organic solvents by lipase from Burkholderia cepacia G63

A lipase from the Burkholderia cepacia strain G63 immobilized on resin was used for the resolution of ketoprofen. To study its catalytic properties in enantioselective esterication, different alcohols and solvents were tested to select the most suitable acyl acceptor and reaction medium. Compared with the low activity of the free lipase, the enzyme activity and E value of the immobilized lipase were significantly enhanced. The enantioselectivity of the immobilized lipase could also be markedly improved by adding a small amount of 18-crown-6. RSM was employed to optimize the reaction parameters. The optimal reaction conditions were: reaction time 22.50 h, additives dosage 0.4322 g (0.33 mmol/mL), and substrate molar ratio 54.11:1. Under optimal conditions, the maximal E value was up to 10.01, which exhibited a better enantioselectivity than some commercial lipases, such as Novozym 435, Lipozyme RM IM and LipozymeTL IM.     

Assessment of two immobilized lipases activity and stability to low temperatures in organic solvents under ultrasound-assisted irradiation

Both stability and catalytic activity of two commercial immobilized lipases were investigated in the presence of different organic solvents in ultrasound-assisted system. In a general way, for Novozym 435, the use of ethanol as solvent led to a loss of activity of 35% after 10 h of contact. The use of iso-octane conducted to a gradual increase in lipase activity in relation to the contact time, reaching a maximum value of relative activity of 126%. For Lipozyme RM IM, after 5 h of exposure, the enzyme presented no residual activity when ethanol was used as solvent. The solvents tert-butanol and iso-octane showed an enhancement of about 20 and 17% in the enzyme activity in 6 h of exposure, respectively. Novozym 435 and Lipozyme IM presented high stability to storage after treatment under ultrasound-assisted system using n-hexane and tert-butanol as solvents.     

Production of extremely pure diacylglycerol from soybean oil by lipase-catalyzed glycerolysis

Research work was objectively targeted to synthesize highly pure diacylglycerol (DAG) with glycerolysis of soybean oil in a solvent medium of t-butanol. Three commercial immobilized lipases (Lipozyme RM IM, Lipozyme TL IM and Novozym 435) were screened, and Novozym 435 was the best out of three candidates. Batch reaction conditions of the enzymatic glycerolysis, the substrate mass ratio, the reaction temperature and the substrate concentration, were studied. The optimal reaction conditions were achieved as 6.23:1 mass ratio of soybean oil to glycerol, 40% (w/v) of substrate concentration in t-butanol and reaction temperature of 50 °C. A two-stage molecular distillation was employed for purification of DAG from reaction products. Scale-up was attempted based on the optimized reaction conditions, 98.7% (24 h) for the conversion rate of soybean oil, 48.5% of DAG in the glycerolysis products and 96.1% for the content of DAG in the final products were taken in account as the results.     

Improved high-pressure enzymatic biodiesel batch synthesis in near-critical carbon dioxide

The enzymatic synthesis of biodiesel by a high-pressure semi-continuous process in near-critical carbon dioxide (NcCO(2)) was studied. Biodiesel synthesis was evaluated in both batch and semi-continuous systems to develop an effective process. Batch processing demonstrated the advantageous properties of NcCO(2) as an alternative reaction medium. Three immobilized lipases (Novozym 435, Lipozyme RM IM, and Lipozyme TL IM from Novozymes) were tested, with Lipozyme TL IM the most effective, showing the highest conversion. Biodiesel conversion from several edible and non-edible oil feedstocks reached >92%. Higher conversion (99.0%) was obtained in a shorter time by employing repeated batch processes with optimized conditions: 44.3 g (500 mM) canola oil, a substrate molar ratio (methanol:oil) of 3:1, an enzyme loading of 20 wt% (of the oil used), at 30 °C, 100 bar, and 300 rpm agitation. The enzyme maintained 80.2% of its initial stability after being reused eight times. These results suggest that this method produces biodiesel energy-efficiently and environment-friendly.     

Immobilized lipase-catalysed synthesis of cinnamyl laurate in non-aqueous media

Esters of cinnamyl alcohol find many applications in food, cosmetic and pharmaceutical industries as flavor and fragrance compounds. The current work focuses on the synthesis of cinnamyl laurate from cinnamyl alcohol and lauric acid, including screening of various immobilized lipases and optimization of reaction conditions such as catalyst loading, speed of agitation, mole ratio and temperature. Among different lipases screened such as Novozym 435, Lipozyme RM IM and Lipozyme TL IM, Novozym 435 was found to be the best catalyst with 60% conversion in 2 h at 30 °C for equimolar quantities of the reactants using 0.33% (w/v) of catalyst and toluene as solvent. An ordered bi–bi mechanism with dead-end complex of lauric acid was found to represent the kinetic data.     

Production of human milk fat substitutes enriched in omega-3 polyunsaturated fatty acids using immobilized commercial lipases and Candida parapsilosis lipase/acyltransferase

In human milk fat (HMF), palmitic acid (20–30%), the major saturated fatty acid, is mostly esterified at the sn-2 position of triacylglycerols, while unsaturated fatty acids are at the sn-1,3 positions, conversely to that occurring in vegetable oils.This study aims at the production of HMF substitutes by enzyme-catalyzed interesterification of tripalmitin with (i) oleic acid (system I) or (ii) omega-3 polyunsaturated fatty acids (omega-3 PUFA) (system II) in solvent-free media. Interesterification activity and batch operational stability of commercial immobilized lipases from Rhizomucor miehei (Lipozyme RM IM), Thermomyces lanuginosa (Lipozyme TL IM) and Candida antarctica (Novozym 435) from Novozymes, DK, and Candida parapsilosis lipase/acyltransferase immobilized on Accurel MP 1000 were evaluated. After 24-h reaction at 60 °C, molar incorporation of oleic acid was about 27% for all the commercial lipases tested and 9% with C. parapsilosis enzyme. Concerning omega-3 PUFA, the highest incorporations were observed with Novozym 435 (21.6%) and Lipozyme RM IM (20%), in contrast with C. parapsilosis enzyme (8.5%) and Lipozyme TL IM (8.2%). In system I, Lipozyme RM IM maintained its activity for 10 repeated 23-h batches while for Lipozyme TL IM, Novozym 435 and C. parapsilosis enzyme, linear (half-life time, t_1/2 = 154 h), series-type (t_1/2 = 253 h) and first-order (t_1/2 = 34.5 h) deactivations were respectively observed. In system II, Lipozyme RM IM showed linear deactivation (t_1/2 = 276 h), while Novozym 435 (t_1/2 = 322 h) and C. parapsilosis enzyme (t_1/2 = 127 h), presented series-type deactivation. Both activity and stability of the biocatalysts depended on the acyl donor used.     

Potential Use of Avocado Oil on Structured Lipids MLM-Type Production Catalysed by Commercial Immobilised Lipases

Structured Lipids are generally constituents of functional foods. Growing demands for SL are based on a fuller understanding of nutritional requirements, lipid metabolism, and improved methods to produce them. Specifically, this work was aimed to add value to avocado oil by producing dietary triacylglycerols (TAG) containing medium-chain fatty acids (M) at positions sn-1,3 and long-chain fatty acids (L) at position sn-2. These MLM-type structured lipids (SL) were produced by interesterification of caprylic acid (CA) (C8:0) and avocado oil (content of C18:1). The regiospecific sn-1,3 commercial lipases Lipozyme RM IM and TL IM were used as biocatalysts to probe the potential of avocado oil to produce SL. Reactions were performed at 30–50°C for 24 h in solvent-free media with a substrate molar ratio of 1∶2 (TAG:CA) and 4–10% w/w enzyme content. The lowest incorporation of CA (1.1% mol) resulted from Lipozyme RM IM that was incubated at 50°C. The maximum incorporation of CA into sn-1,3 positions of TAG was 29.2% mol. This result was obtained at 30°C with 10% w/w Lipozyme TL IM, which is the highest values obtained in solvent-free medium until now for structured lipids of low-calories. This strategy opens a new market to added value products based on avocado oil.     

Influence of compressed fluids treatment on the activity of Yarrowia lipolytica lipase

This work investigated the influence of temperature, pressure, exposure times and depressurization rate on the activity of a non-commercial immobilized lipase from Yarrowia lipolytica (YLL) submitted to compressed carbon dioxide, propane and n-butane. A high-pressure cell was employed in the experiments, in the pressure range of 10–280 bar, varying the temperature from 35 to 75 °C, exposure times from 1 to 6 h, and adopting distinct decompression rates. Results showed that significant activity losses were obtained when the treatment was conducted in carbon dioxide, while negligible losses were observed in both propane and n-butane. For the treatment with carbon dioxide, within the range studied, the decompression rate affected positively enzyme activity, while the exposure time and temperature presented an opposite effect on the non-commercial immobilized lipase from Y. lipolytica (YLL). Additionally, the performance of two commercial immobilized lipases (Lipozyme IM and Novozym 435) and the immobilized YLL in the three solvents was compared. Immobilized YLL has shown to be more suitable than Lipozyme IM for enzyme-catalyzed reactions using compressed propane and n-butane as solvents, but with inferior performance compared to Novozym 435 treated in these solvents.     

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.     

Improvement of enzymatic biodiesel production by controlled substrate feeding using silica gel in solvent free system

A silica gel-based substrate feeding system was developed to prevent methanol inhibiting the catalyst during enzymatic biodiesel synthesis. In the system, silica gel swelled upon methanol addition and subsequently released it in a controlled manner to prevent excess methanol affecting the enzyme. Biodiesel was synthesized by the enzymatic transesterification of canola oil with methanol. For this reaction, enzyme loading, methanol/oil molar ratio, silica gel dosage, glycerol content, and methanol feeding method were tested using commercial immobilized enzymes (Novozym 435 and Lipozyme RM IM from Novozymes). The results showed that conversion was highest with controlled substrate feeding rather than direct methanol addition, suggesting that the method developed here can easily prevent enzyme inhibition by limiting methanol concentration to an acceptable level.     

Process intensification of immobilized lipase catalysis by microwave irradiation in the synthesis of 4-chloro-2-methylphenoxyacetic acid (MCPA) esters

4-Chloro-2-methylphenoxyacetic acid (MCPA) is a selective systemic herbicide which is absorbed by leaves and roots. MCPA esters are preferred due to their low water solubility and environmental friendliness. Esterification of MCPA with n-butanol was investigated as a model reaction using immobilized enzymes under the influence of microwave irradiation. Different immobilized enzymes such as Novozym 435, Lipozyme TL IM, Lipozyme RM IM and Lipase AYS Amano were studied under microwave irradiation amongst which Novozym 435 (immobilized Candida antarctica lipase B) was the best catalyst. Effects of various parameters were systematically studied on rates and conversion. Under microwave irradiation, the initial rates were observed to increase up to 2-fold. Under optimized conditions of 0.1 mmol MCPA and 0.3 mmol n-butanol in 15 mL 1,4-dioxane as solvent, Novozym 435 showed a conversion of 83% at 60 °C in 6 h. Based on initial rate and progress curve data, the reaction was shown to follow the Ping Pong bi–bi mechanism with inhibition by MCPA and n-butanol. Esterification of MCPA was also studied with different alcohols such as isopropyl alcohol, n-pentanol, n-hexanol, benzyl alcohol and 2-ethyl-1-hexanol.     

Mass-spectrometry-linked screening of protein fractions for enzymatic activities--a tool for functional genomics

A simple and rapid strategy is described to screen protein fractions for defined enzymatic activity. A protein fraction from a porcine kidney extract was immobilized by covalent coupling to activated affinity beads. The immobilized proteins were incubated with probes specific for different enzyme activities. The reaction products were analyzed by matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry. The MALDI spectra indicate the presence of 5'-nucleotidase, phosphatase, kinase, glutathione reductase, and renin activities in the kidney protein extract. Furthermore, the method can be used to screen for inhibitors of enzymatic reactions. The method is adaptable to high-throughput sample handling and automated mass spectrometric analysis and therefore suited for functional genomics.     

Lipase catalyzed synthesis of benzyl acetate in solvent-free medium using vinyl acetate as acyl donor

Use of vinyl acetate as acyl donor in transesterification of benzyl alcohol catalyzed by a commercially available lipase (Lipozyme RM IM) gave 100% conversion in 10 min. The excess acyl donor and the enzyme could be recovered and reused. Unlike the chemical catalytic processes, it produced no undesirable side product.     

Mass-Spectrometry-Linked Screening of Protein Fractions for Enzymatic Activities—A Tool for Functional Genomics

A simple and rapid strategy is described to screen protein fractions for defined enzymatic activity. A protein fraction from a porcine kidney extract was immobilized by covalent coupling to activated affinity beads. The immobilized proteins were incubated with probes specific for different enzyme activities. The reaction products were analyzed by matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry. The MALDI spectra indicate the presence of 5′-nucleotidase, phosphatase, kinase, glutathione reductase, and renin activities in the kidney protein extract. Furthermore, the method can be used to screen for inhibitors of enzymatic reactions. The method is adaptable to high-throughput sample handling and automated mass spectrometric analysis and therefore suited for functional genomics.     

Combinations of SPR and MS for characterization of native and recombinant proteins in cell lysates

Surface plasmon resonance and mass spectrometry (SPR-MS) has been combined for quality check of recombinant 6xHis-tagged 14-3-3 proteins expressed in Escherichia coli. Lysates were injected over an SPR sensorchip with immobilized Ni²⁺ for SPR analysis of the specific Ni²⁺ binding response and stability. To validate the identity, intactness and homogeneity of the captured proteins were eluted for mass spectrometric analysis of intact molecular weight and peptide mass mapping. Additionally, the captured recombinant proteins were investigated for specific binding to known phosphorylated ligands of 14-3-3 proteins in order to test their activity. Specific binding of recombinant and native 14-3-3 proteins in complex mixtures to immobilized phosphopeptides and subsequent elution was also tested by SPR-MS. Ammonium sulfate precipitate fractions from lysates of E. coli expressing 14-3-3 protein and of cauliflower were investigated for specific binding to the phosphopeptide ligands immobilized on a sensorchip by SPR. Subsequently, the bound protein was eluted and analyzed by MS for characterization of intact mass and peptide mass mapping.     

Identification of mouse brain proteins associated with isoform 3 of metallothionein

Using immunological approaches and mass spectrometry, five proteins associated with metallothionein-3 in mouse brains have been identified. Metallothionein-3 and associated proteins were isolated using immunoaffinity chromatography over immobilized anti-mouse brain MT3 antibody. Proteins in the recovered pool were separated by SDS-polyacrylamide gel electrophoresis, and distinct bands were excised and the proteins digested using trypsin. Peptides were extracted and analyzed using electrospray ionization mass spectrometry. Initial identification was done comparing the identified peptide mass:charge ratios to the MASCOT database. Confirmation of proteins was accomplished by sequencing of selected peptides using tandem mass spectrometry and comparison to the MASCOT database. The proteins were heat-shock protein 84 (mouse variant of heat-shock protein 90), heat-shock protein 70, dihydropyrimidinase-like protein 2, creatine kinase, and beta actin. Independently using antibodies against metallothionein-3, creatine kinase, and heat-shock protein 84 showed that all three proteins were coimmunoprecipitated from whole mouse brain homogenates with each of the three antibodies. Mixing purified samples of metallothionein and human brain creatine kinase also generated a complex that could be immunoprecipitated either by anti-metallothionein-3 or anticreatine kinase antibody. These data are consistent with metallothionein-3 being present in the mouse brain as part of a multiprotein complex providing new functional information for understanding the role of metallothionein-3 in neuronal physiology.     

Genomic analysis of biochemical function

Establishing the linkage between an individual biochemical activity and the gene(s) specifying that activity has been facilitated by advances in mass spectrometry and affinity purification methods. In addition, a genomic protein array has been produced in yeast by fusing each yeast open reading frame to glutathione-S-transferase, thus linking each protein with its cognate gene. Purification and biochemical assay of pools of glutathione-S-transferase-open-reading-frame proteins allows analysis of the entire proteome for biochemical activities, followed by simple deconvolution to identify the responsible open reading frame. An alternative method to analyze large sets of proteins is the use of protein microarrays in which over 10,000 individual proteins can be immobilized and assayed on a single slide.     

脂肪酶协同催化猪油合成生物柴油工艺研究

探讨了以乙酸甲酯为酰基受体两种脂肪酶协同催化猪油转酯合成生物柴油的工艺条件。首先利用单因子试验确定2种固定化脂肪酶Novozym435、Lipozyme TLIM单独作为催化剂时的最佳酶用量为40％,反应温度为50℃,乙酸甲酯用量为14（相对于油的摩尔比）。在此基础上,采用3因素5水平和3个中心点的中心组分旋转设计法研究了上述2种脂肪酶协同使用时脂肪酶用量（g/g）、混合酶的配比（%/%）以及乙酸甲酯用量诸因素共同作用对转酯反应转化率的影响。优化后的反应条件为：总酶用量为40％,混合酶配比为50/50,乙酸甲酯用量为14,在该条件下甲酯得率可达97.6％,比同质量的Novozym435、Lipozyme TLIM的催化活性分别高出7.6％、22.3％。表明脂肪酶协同催化猪油合成生物柴油工艺可以较好地提高甲酯得率,并且节约生产成本。