Hydrolysis of used frying palm olein and sunflower oil catalyzed by porcine pancreatic lipase

The enzymatic hydrolysis of frying used vegetable oils with different degrees of alteration were measured using porcine pancreatic lipase (acylglycerol acylhydrolase EC 3.1.1.3). Successive frying of potatoes significantly increased the level of total polar lipid content in the palm olein from 9.3±0.1 mg/100 mg oil to 26.4±0.3 mg/100 mg oil after 90 fryings, and from 4.0±0.1 mg/100 mg oil to 27.7±0.3 mg/100 mg oil in sunflower oil after 60 fryings. Triacylglycerol polymers, triacylglycerol dimers, and oxidized triacylglycerols also increased 37-, 7.9-, and 7.5-times in palm olein, respectively, and 56-, 22-, and 4.7-times in sunflower oil, respectively. However, diacylglycerols and free fatty acid levels related to hydrolytic alteration did not increase with the number of fryings in both oils. The substrate concentration in the reactor was determined by calculating the molecular weight of each oil showing a different degree of alteration. We compared the methodology used by us and that used by other authors. The results show that the methods are reproducible and that the values obtained are in concordance with theoretical values. The kinetic parameters apparent Michaelis-Menten constant (K _M ^app ) and apparent maximum velocity of hydrolysis (V _max ^app ) were different in unused palm olein (5.1±0.7 and 166±7.6, respectively) than in sunflower oil (2.2±0.3 and 62±2.2, respectively). However, changes inK _M ^app andV _max ^app were not related to the degree of alteration of the oils.     

A kinetic model for enzymatic reactions in reverse micellar systems involving water‐insoluble substrates and enzyme activators

The activity of Chromobacterium viscosum lipase (glycerol‐ester hydrolase, EC 3.1.1.3) entrapped in AOT/isooctane reverse micelles was significantly increased by the addition of short chain polyethylene glycols (PEGs) or methoxypolyethylene glycols (MPEGs) for the hydrolysis of olive oil. To understand enzyme activity in the presence of PEG 400 or MPEG 550 molecules, a kinetic model was proposed. The validity of this model was verified by experimental data on the lipase‐catalyzed hydrolysis of olive oil in AOT/isooctane reverse micellar systems, in which PEG 400 or MPEG 550 had been added. The large value of the equilibrium constant (k_D) for enzyme activation indicated that the affinity between C viscosum lipase and PEG 400 or MPEG 550 molecules was very strong. The Michaelis constant (K_m) predicted by the proposed model explained enzymatic reactions more exactly than that by the previously published model. Copyright © 2003 Society of Chemical Industry     

A kinetic model for enzymatic reactions in a reverse micellar system,involving water-insoluble substrate

A kinetic model was proposed for enzymatic reactions in a reverse micellar system, involving a water-insoluble substrate. Though surfactant is one of the main structural components of reverse micelles, an increase in the surfactant concentrations affects the enzyme activity remarkably. A relationship between the enzyme activity and the surfactant concentration is discussed. In this study it was assumed that free substrate in the organic phase was in adsorption equilibrium with the surface of the micellar surfactant, and that the adsorption coefficient and the true K_m value (Michaelis constant) were independent of the surfactant concentration. The validity of this model was verified by data on the hydrolysis of olive oil, catalyzed by Chromobacterium viscosum lipase (Glycerol-ester hydrolase; EC 3.1.1.3) in an AOT/isooctane reverse micellar system. The activity value predicted by the model equation agreed well with the experimental data.     

Protein hydrolysis under anaerobic,saline conditions in presence of acetic acid

The hydrolysis of soluble proteins in an anaerobic, saline (24 g dm^?3 NaCl) and mesophilic (37 °C) environment was studied. The inhibitory effect of a volatile fatty acid, acetic acid (HAc), on the hydrolysis rate and hydrolytic biomass activity for a model saline wastewater with a high protein load (total organic carbon, 1153 mg dm^?3 and 1572 mg dm^?3 proteins) was studied. Initial inhibitor concentrations were tested in the range of 0–2000 mg dm^?3 HAc. The microbiological characterization was performed using a total microorganism count by epifluorescence, and hydrolytic bacterial activity was determined by plate count. The protein hydrolysis was modeled according to first order kinetics. The effect of biomass on hydrolysis was analyzed by varying its concentration in the range of 42–210 mg dm^?3 volatile suspended solids. The following apparent hydrolysis kinetic constants (K_h) for proteins at 37 °C were obtained: 1.3, 0.8, 0.6, 0.2 and 0.1 d^?1 for initial concentrations of 250, 500, 750, 880, and 1000 mg dm^?3 HAc, respectively. At concentrations of HAc greater than 1000 mg dm^?3, total inhibition of hydrolysis was observed. The intrinsic hydrolysis constant ( ) at 37 °C, without inhibition, was 2.3 d^?1. The hydrolysis kinetic constant was not affected by the biomass concentration. The hydrolysis kinetics constant was filted to three models: Luong, Levenspiel and non‐competitive inhibition. The model that best represented the experimental data was Luong, obtaining an inhibition constant (K_I) of 1087 mg dm^?3 of HAc and the exponent γ = 0.54. The hydrolysis was inhibited by the presence of HAc, which corresponds to an intermediate compound of the anaerobic process. Copyright © 2004 Society of Chemical Industry     

Effects of structural features of cotton cellulose on enzymatic hydrolysis

Textile cotton wastes were treated with γ rays and 18% NaOH and 70% ZnCl₂ solutions and were subjected to enzymatic hydrolysis. The untreated and treated samples were characterized both before and after hydrolysis by means of parameters concerning molecular structure (degree of polymerization), supermolecular structure (x-ray diffraction), accessibility, and reactivity (moisture regain, enzyme adsorption, and solubility in FeTNa). These parameters were correlated to kinetic parameters of the hydrolysis reaction. The V_max and K_m values were evaluated from Lineweaver–Burk plots at different temperatures. The V_max/K_m ratio, analogous to the specificity constant, proved to be less sensitive to experimental errors and more suitable for a comparison of the kinetic behavior of the samples. The modifications of both supermolecular structure and morphology of cellulose were of primary importance to attain high yields and rates of hydrolysis. Furthermore, the structural and morphologic parameters chosen to characterize the samples can be correlated to the kinetic parameters of enzymatic hydrolysis, in particular to K_m values.     

Treatment of olive mill wastewaters by ozonation,aerobic degradation and the combination of both treatments

The degradation of the pollutant organic matter present in olive oil mill wastewaters (OMW) is carried out by a single ozonation, a single aerobic degradation, and the combination of two successives steps: an ozonation followed by an aerobic degradation, and an aerobic degradation followed by an ozonation. In both single processes, the removal of this contaminant load is followed by means of global parameters which are directly related to the concentration of organic compounds in those effluents: chemical oxygen demand and total aromatic and phenolic contents. In the ozonation, an approximate kinetic study is performed which leads to the evaluation of the apparent kinetic constants for the aromatic reduction, k_A. In the aerobic degradation, the kinetic study is conducted by using the Grau model, which is applied to the experimental data, and leads to the determination of the kinetic parameters of this model, K₂ and n. In the combined processes, a higher COD global reduction is obtained by the successive stages, and an improvement in the removal of the organic material during the second treatment of both processes due to the pretreatment conducted is also observed. This enhancement is shown by an increase of the kinetic parameters (K₂ and n in the aerobic degradation of the pre‐ozonated wastewaters; the apparent constant k_A in the ozonation of the wastewaters preliminary fermented aerobically), in relation to the values obtained for them in the single processes carried out at the same operating conditions. © 1999 Society of Chemical Industry     

Parameter sensitivity of kinetics-based hydrometallurgical reactor models

In this paper, we have studied the parameter sensitivity of two hydrometallurgical models: REACTSIM (for gold pressure oxidation) and ZINCSIM (for zinc pressure leaching). The parameters investigated include: the oxygen mass transfer coefficient, k_La, the activation energy for pyrite oxidation, E_a, pyrite and marmatite dissolution stoichiometry, the constant kinetic parameter for ferrous to ferric oxidation and the apparent equilibrium constant for ferric precipitation, K_E. Model predictions were found to be more sensitive to the kinetic parameters under certain conditions than others. For ferrous to ferric oxidation kinetics, a dramatic model sensitivity was found to the constant kinetic parameter with an apparent discontinuity at values close to those found in bench scale experiments. The usefulness of simulation programs was demonstrated when non-intuitive results were obtained showing ZINCSIM sensitivity to sulphate production to be opposite from what was expected. In the case of K_E, solution chemistry was not as sensitive as the heat balance, which was affected significantly.     

Pretreatment of Chromobacterium viscosum lipase with acetone increases its activity in sodium bis‐(2‐ethylhexyl) sulfosuccinate (AOT) reverse micelles

The activity of Chromobacterium viscosum lipase for hydrolysis of olive oil in sodium bis‐(2‐ethylhexyl) sulfosuccinate (AOT) reverse micelles was increased by pretreatment with acetone. In contrast to the untreated lipase, no sharp fall in the activity of the treated lipase at higher W₀ (water to AOT molar ratio) values was observed. The fluorescence emission intensity of the treated lipase in reverse micelles was higher than that of the untreated lipase but the maximal emission wavelength (λ_max) was the same for both lipases. A kinetic model that considers the free substrate in equilibrium with the substrate adsorbed on the micellar surface was successfully used to better understand the activity enhancement. The Michaelis constant (K_m) and substrate adsorption equilibrium constant (K_ad) were reduced by lipase pretreatment with acetone whereas the maximum reaction rate (v_max) remained unaltered. Copyright © 2005 Society of Chemical Industry     

Continuous Methanolysis of Palm Oil Using a Liquid–Liquid Film Reactor

A system for the continuous methanolysis of palm oil using a liquid–liquid film reactor (LLFR) was developed and characterized. This reactor is a co-current, constant diameter (0.01 m), custom-made packed column where the mass transfer area between the partially miscible methanol-rich and vegetable oil-rich phases is created in a non-dispersive way, without the intervention of mechanical stirrers or ultrasound devices. An increase in contact area between phases enhances reaction rate while the absence of small, dispersed droplets of one phase into the other diminishes the settling time at the end of the reaction. In this study variations on the concentration of catalyst (sodium hydroxide), flow rate of palm oil and normalized length of the reactor (L/L _max) were explored, keeping constant both the methanol to oil molar ratio and the temperature of the reaction (6:1 and 60 °C). The best experimental results with a reactor of 1.26 m (L/L _max = 1.0) showed a conversion of palm oil of 97.5% and a yield of methyl esters of 92.2% of the theoretical yield, when the mass flow rate and the residence time of the palm oil were 9.0 g min⁻¹ and 5.0 min, respectively. To determine the mean residence time and the degree of axial mixing in the reactor, a residence time distribution (RTD) study was performed using a step-function input. The dispersion model appears to fit well the RTD experimental data.     

Photodegradation of Famotidine by Integrated Photocatalytic Adsorbent (IPCA) and Kinetic Study

Abstract  

Integrated photocatalytic adsorbents (IPCAs) comprised of nanocrystalline titanium dioxide (TiO₂) and activated carbon (AC) were prepared using an ultrasonic impregnation technique. The IPCAs were characterised by scanning electron microscopy (SEM) and Fourier-transform infrared (FT-IR) spectroscopy and were employed as catalysts for the photodegradation of famotidine-an active pharmaceutical ingredient-in aqueous solutions using illumination from a 125 W medium pressure mercury lamp. The degradation kinetics were found to follow a pseudo-first-order rate law and varying TiO₂ loadings induced different increases in the apparent first-order rate constant of the process. The kinetic behaviour can be described in terms of a modified Langmuir–Hinshelwood (LH) model. The IPCA prepared using a 10% TiO₂ to AC loading exhibited the highest rate constant with a K _C and k _r of 0.0172 L/mg and 0.237 mg/L/min, respectively. The LH model fits the experimental data and elucidates the effect of the TiO₂ content of the IPCA on the degradation rate. The use of calcination (heat treatment) in IPCA preparation and its effect on photocatalytic and adsorption performance were also investigated. The present work demonstrates that the combination of TiO₂ and AC results in a promising material for application in the degradation of organic pollutants.     

Desorption of free radicals in semibatch emulsion polymerization of methyl acrylate

Desorption of free radicals from particles can cause an emulsion polymerization system to deviate from Smith–Ewart case II kinetics. A mechanistic model has been developed to predict the effect of desorption of radicals from particles on the kinetics of semibatch emulsion polymerization of methyl acrylate under the monomer-starved condition. Experimental data available in the literature are used to assess the proposed kinetic model. The model predicts the experimental data reasonably well for a wide range of monomer feed rates. The rate of polymerization increases with an increase in the rate of monomer addition. The kinetic data are also useful in evaluating the desorption rate constant (K′_d) for methyl acrylate. The best fitted value of K′_d at 50°C is 4 × 10^-12 cm²/s, which is in good agreement with the theoretical values predicted by desorption theory. © 1995 John Wiley & Sons, Inc.     

Increased activity of Chromobacterium viscosum lipase in AOT reverse micelles in the presence of short chain methoxypolyethylene glycol

The activity of Chromobacterium viscosum lipase (glycerol‐ester hydrolase, EC 3.1.1.3) entrapped in AOT/isooctane and AOT/Tween 85/isooctane reverse micelles was significantly increased by the addition of short chain methoxypolyethylene glycols (MPEGs), taking the hydrolysis of olive oil as a model reaction. The molecular weight of MPEG had a strong effect on the lipase activity, and MPEG of nominal molecular weight 550 was found to be the most effective. To optimize the factors affecting enzymatic hydrolysis of olive oil in reverse micellar systems containing MPEG 550, the effect of various parameters, such as W_o (molar ratio of water to surfactant), pH, ionic strength, surfactant concentration and temperature were investigated. A kinetic model considering the substrate adsorption equilibrium between the bulk phase of organic solvent and the micellar phase was also successfully used to understand the enzyme activity in the presence of MPEG 550. Both the Michaelis constant and the substrate adsorption equilibrium constant were obviously reduced as compared with those obtained in the simple AOT reverse micellar system. © 2001 Society of Chemical Industry     

Production of lipase from Penicillium sp. using waste oils and Nopalea cochenillifera

The present communication deals with the production of lipase from Penicillium sp. using waste oils and palm cactus (Nopalea cochenillifera) especially as nutrient source of low cost. Two different waste oils were tested: waste frying oil from an industrial kitchen and waste lubricating oil (WLO) from a gas station. Using Doehlert experimental design and response surface methodology, the optimum conditions for lipase production were 96?h fermentation, WLO as the inductor, with specific activity of 0.22?UA?mg^?1. The enzyme was able to remain with more than 58% of its original activity until 30?min at 60°C. The kinetic constants were K_m?=?9.93?mM and V_max?=?2.58 UA min^?1 using p-nitrophenyl palmitate (p-NPP) as substrate. Results showed that Penicillium sp. was able to produce lipase from waste oils using N. cochenillifera, thus having biotechnological potential in waste oil biotransformation.     

Thermoxidation of substrate models and their behavior during hydrolysis by porcine pancreatic lipase

The behavior of thermoxidized triacylglycerols during hydrolysis catalyzed by porcine pancreatic lipase was evaluated using nonpolar triacylglycerols isolated from palm olein (NPTPO), triolein, and sn-1,3 diolein substrates. Substrates were thermoxidized at 180°C for 1 to 4 h. Owing to formation of polymers and dimers of triacylglycerols, the molecular weight of the thermoxidized substrates increased. After 1 h heating, the concentration of polymers and dimers was similar for the sn-1-3 diolein and triolein samples but higher in NPTPO samples. Conjugated double bonds were formed in all samples, and α,β-unsaturated carbonyl compounds developed through allylic oxidations. These caused increased ultraviolet absorbance at 232 nm. The hydrolysis of heated and unheated samples by the lipase can be described by a Michaelian equation. The enzyme showed a higher apparent V _max and K _M with heated sn-1,3 diolein and triolein than with their unheated counterparts. This was due to the generation of polar compounds which acted as emulsifiers and which favored the formation of an oil/water microemulsion. This behavior was not observed in NPTPO, where heating decreased the apparent V _max and K _M over the first 2 h. Later, a tendency to increase these values was observed. The results could be explained by a balance between concentration of surfactants and of natural emulsifiers in the thermoxidized samples.     

Adsorption Isotherms for Bleaching Soybean Oil with Activated Attapulgite

Activated attapulgite was characterized and used as bleaching clay (adsorbent) for soybean oil. Adsorption isotherms for bleaching soybean oil were determined to investigate the applicability of the Langmuir and Freundlich equations and to elucidate the adsorption characteristics of oil on activated attapulgite. The Freundlich model was found to provide a better fit with the experimental data than the Langmuir model. The larger Freundlich constant, K _F at higher temperature indicated more effective adsorption. The heat evolved for oil bleaching increased as the levels of activated attapulgite increased from 0.5 to 3%, due to the increase in adsorptive sites with increasing attapulgite levels as well as multilayer adsorption driven by van der Waals’ forces at smaller amounts of adsorbents. There are enough adsorptive sites with 3% attapulgite to adsorb the pigments associated with soybean oil bleaching. The amount of attapulgite has no effect on ΔH _a when it is >3%, and ΔH _a is about 32 kJ/mol.     

Kinetics of carbon dioxide and methane hydrate formation

Experimental data on the kinetics of carbon dioxide hydrate formation and its solubility in distilled water are reported. The experiments were carried out in a semi-batch stirred tank reactor at nominal temperatures of 274, 276 and 278 K and at pressure ranging from 1.59 to 2.79 MPa for the kinetics experiments and at pressure ranging from 0.89 to 2.09 MPa for the solubility experiments. A minor inconsistency in the kinetic model developed by Englezos et al. (1987a) was removed and the model was modified to determine the intrinsic kinetic rate constant for carbon dioxide hydrate formation. The same model was also used to re-determine the intrinsic kinetic rate constant for methane hydrate formation. The model is based on the crystallization theory coupled with the two-film theory for gas absorption in the liquid phase. The Henry's constant (H) and apparent dissolution rate constant (K_La) required in the model were determined using the experimental solubility data. The kinetic model describes the experimental data very well. The kinetic rate constant obtained for the carbon dioxide hydrate formation was found to be higher than that for methane.     

Kinetics of Palm Oil Methanolysis

A kinetics study of palm oil methanolysis was conducted at three different temperatures and three different concentrations of catalyst, sodium hydroxide, keeping constant the molar ratio of methanol to oil and the rotational speed of the impeller (6:1 and 400 rpm). The maximum conversion of palm oil and productivity to methyl esters were obtained at 60 °C and 1 wt% of NaOH based on palm oil, and they were 100 and 97.6%, respectively. The statistical analysis of conversions of palm oil and productivities to methyl esters as functions of temperature and concentration of catalyst, after 80 min of reaction, allowed them to fit second order polynomial equations, which adequately describe the experimental behavior. The experimental data appear to be a good fit into a second order kinetic model for the three stepwise reactions, and the reaction rate constants and the activation energies were determined. In this article we present the kinetic constant and activation energies for the experiments with 0.2% wt of NaOH. The effect of molar ratio on the concentration of products was investigated, while the temperature (55 °C), the concentration of catalyst (0.60 wt% of NaOH), and the rotational speed (400 rpm), were held constant. The results showed that the conversion and the productivity increased due to methanol excess, and were higher for the reactions with a molar ratio of 6:1.     

CORN GLUTEN HYDROLYSIS BY ALCALASE: KINETICS OF HYDROLYSIS

In the present study, the reaction kinetics of corn gluten hydrolysis by Alcalase, a bacterial protease produced by Bacillus licheniformis, was investigated. The reactions were carried out for 10 min in 0.1 L of aqueous solutions containing 10, 20, 30, 40, and 50 g protein L^?1 corn gluten at various temperature and pH values. The amount of enzyme added to the reaction solution was 0.25% (v/v). Also, to determine decay and product inhibition effects for Alcalase, a series of inhibition experiments were conducted with the addition of various amounts of hydrolysate. For each experimental run, both the amount of hydrolysis (meqv L^?1) and the soluble protein amount (g L^?1) were investigated with respect to time, and the initial reaction rates were determined from the slopes of the linear models that fitted to these experimental data. The kinetic parameters, K_m and V_max were estimated as 53.77 g L^?1 and 5.94 meqv L^?1min^?1. The type of inhibition for Alcalase was determined as uncompetitive, and the inhibition constant, K_i, was estimated as 44.68% (hydrolysate/substrate mixture).     

亚临界水萃取植物精油的模型

Mechanisms that control the extraction rate of essential oil from Zataria multiflora Boiss. (Z. multiflora) with subcritical water (SW) were studied. The extraction curves at different solvent flow rates were used to determine whether the extractions were limited primarily by the near equilibrium partitioning of the analyte between the matrix and solvent (i.e. partitioning thermodynamics) or by the rates of analyte desorption from the matrix (i.e. ki-netics). Four simple models have been applied to describe the extraction profiles obtained with SW: (1) a model based solely on the thermodynamic distribution coefficient KD, which assumes that analyte desorption from the ma-trix is rapid compared to elution; (2) one-site kinetic model, which assumes that the extraction rate is limited by the analyte desorption rate from the matrix, and is not limited by the thermodynamic (KD) partitioning that occurs dur-ing elution; (3) two-site kinetic model and (4) external mass transfer resistance model. For SW extraction, the thermodynamic elution of analytes from the matrix was the prevailing mechanism as evidenced by the fact that ex-traction rates increased proportionally with the SW flow rate. This was also confirmed by the fact that simple re-moval calculations based on determined KD (for major essential oil compounds) gave good fits to experimental data for flow rates from 1 to 4 ml•min－1. The results suggested that the overall extraction mechanism was influenced by solute partitioning equilibrium with external mass transfer through liquid film.     

Enzymatic activity of Chromobacterium viscosum lipase in an AOT/Tween 85 mixed reverse micellar system

To enhance the Chromobacterium viscosum lipase (glycerol‐ester hydrolase; EC 3.1.1.3) activity for the reaction of water‐insoluble substrates, the AOT/isooctane reverse micellar interface was modified by co‐adsorption of a non‐ionic surfactant. Polyoxyethylene sorbitan trioleate (Tween 85) was used as the non‐ionic surfactant and olive oil as a water‐insoluble substrate. An appreciable increase of lipase activity was observed and at higher W_o values (where W_o = molar ratio of water to total surfactants of the micellar system) there was no sharp fall of the enzyme activity such as a typical bell‐shaped profile. The kinetic model for the lipase‐catalysed hydrolysis of olive oil in AOT/isooctane reverse micellar system was applied to the enzymatic reaction in this mixed reverse micellar system. It was found that the predictions of the model agree well with the experimental kinetic results and that the adsorption equilibrium constant of olive oil molecules between the micellar phase and the bulk phase of the organic solvent is smaller in AOT/Tween 85 mixed reverse micellar systems than in simple AOT reverse micellar systems. © 1999 Society of Chemical Industry