Débora de Oliveira

Optimization of Enzymatic Production of Biodiesel from Castor Oil in Organic Solvent Medium

We studied the production of fatty acid ethyl esters from castor oil using n-hexane as solvent and two commercial lipases, Novozym 435 and Lipozyme IM, as catalysts. For this purpose, a Taguchi experimental design was adopted considering the following variables: temperature (35–65°C), water (0–10 wt/wt%), and enzyme (5–20 wt/wt%) concentrations and oil-to-ethanol molar ratio (1∶3 to 1∶10). An empirical model was then built so as to assess the main and cross-variable effects on the reaction conversion and also to maximize biodiesel production for each enzyme. For the system containing Novozym 435 as tatalyst the maximum conversion obtained was 81.4% at 65°C, enzyme concentration of 20 wt/wt%, water concentration of 0 wt/wt%, and oil-to-ethanol molar ratio of 1∶10. When the catalyst was Lipozyme IM, a conversion as high as 98% was obtained at 65°C, enzyme concentration of 20 wt/wt%, water concentration of 0 wt/wt%, and oil-to-ethanol molar ratio of 1∶3.

Enzymatic alcoholysis of palm kernel oil in n-hexane and SCCO2

Abstract The use of biocatalysts in supercritical CO 2 (SCCO 2 ) has received widespread attention in recent years. Biocatalysts have the advantage of substrate specificity under mild reaction conditions and SCCO 2 has several advantages over liquid solvents such as high solute diffusivities and low viscosity, which can accelerate mass transfer-limited enzymatic reactions. Concerning the enzymatic alcoholysis of vegetable oils, very little experimental data have been reported in the literature. Also, to the best of our knowledge, there is no comprehensive study available comparing conventional and supercritical media for this reaction. In this context, the main objective of this work is to compare enzymatic ethanolysis of palm kernel oil taking place in both SCCO 2 and in n -hexane as solvents. For this purpose, a Taguchi experimental design with two levels and four variables was adopted for each system to allow the investigation of the influence of process variables on the reaction conversion and on the enzyme activity.

Ultrasound-assisted lipase-catalyzed transesterification of soybean oil in organic solvent system.

This work reports the transesterification of soybean oil with ethanol using two commercial immobilized lipases under the influence of ultrasound irradiation. The experiments were performed in an ultrasonic water bath, following a sequence of experimental designs to assess the effects of temperature, enzyme and water concentrations, oil to ethanol molar ratio and output irradiation power on the reaction yield. Results show that ultrasound-assisted lipase-catalyzed transesterification of soybean oil with ethanol might be a potential alternative route to conventional alkali-catalyzed method, as high reaction yields (~90 wt.%) were obtained at mild irradiation power supply (~100 W), and temperature (60 °C) in a relatively short reaction time, 4h, using Lipozyme RM IM as catalyst. The repeated use of the catalyst under the optimum experimental condition resulted in a decay in both enzyme activity and product conversion after two cycles. The use of Novozym 435 led to lower conversions (about 57%) but the enzyme activity was stable after eight cycles of use, showing, however, a reduction in product conversion after the forth cycle.

Effect of temperature, moisture, and carbon supplementation on lipase production by solid-state fermentation of soy cake by Penicillium simplicissimum

The production of lipases by Penicillium simplicissimum using solid-state fermentation and soy cake as substrate was investigated. The effects of temperature, cake moisture, and carbon supplementation on lipase production were studied using a two-level experimental plan. Moisture, pH, and lipase activity were followed during fermentation. Statistical analysis of the results was performed to evaluate the effect of the studied variables on the maximum lipase activity. Incubation temperature was the variable that most affected enzyme activity, showing a negative effect. Moisture and carbon supplementation presented a positive effect on activity. It was possible to obtain lipase activity as high as 21 U/g of dry cake in the studied range of process variables.

Optimization of alkaline transesterification of soybean oil and castor oil for biodiesel production

This article reports experimental data on the production of fatty acid ethyl esters from refined and degummed soybean oil and castor oil using NaOH as catalyst. The variables investigated were temperature (30–70°C), reaction time (1–3 h), catalyst concentration (0.5–1.5 w/wt%), and oil-to-ethanol molar ratio (1:3–1:9). The effects of process variables on the reaction conversion as well as the optimum experimental conditions are presented. The results show that conversions >95% were achieved for all systems investigated. In general, an increase in reaction temperature, reaction time, and in oil-to-ethanol molar ratio led to an enhancement in reaction conversion, whereas an opposite trend was verified with respect to catalyst concentration.

Ultrasound irradiation promoted efficient solvent-free lipase-catalyzed production of mono- and diacylglycerols from olive oil.

This work reports the enzymatic production of mono- and diacylglycerols under the influence of ultrasound irradiation, in a solvent-free system, with and without the presence of surfactants at a constant temperature of 65°C, glycerol to oil molar ratio of 2:1 and a commercial immobilized lipase (Novozym 435) as catalyst. For this purpose, two operation modes were adopted: the use of a sonotrode (ultrasonic probe), without agitation, varying reaction time, irradiation amplitude (25-45% of the total power) and type of surfactant, and a mechanically stirred reactor (600 rpm) under ultrasound irradiation in a water bath, testing different surfactants. Results show that very satisfactory MAG and DAG yields, above 50 wt.%, can be obtained without the use of surfactant, at mild irradiation power supply (∼130 W), with no important enzyme activity losses verified, in a relatively short reaction time (2h), and low enzyme content (7.5 wt.%). Also, reaction kinetic results show that contents of MAG+DAG as high as ∼65 wt.% can be achieved at longer times (6h), indicating a promising route for producing MAG and DAG using ultrasound irradiation.

Role for Golgi reassembly and stacking protein (GRASP) in polysaccharide secretion and fungal virulence.

Secretion of virulence factors is a critical mechanism for the establishment of cryptococcosis, a disease caused by the yeast pathogen Cryptococcus neoformans. One key virulence strategy of C. neoformans is the release of glucuronoxylomannan (GXM), a capsule‐associated immune‐modulatory polysaccharide that reaches the extracellular space through secretory vesicles. Golgi reassembly and stacking protein (GRASP) is required for unconventional protein secretion mechanisms in different eukaryotic cells, but its role in polysaccharide secretion is unknown. This study demonstrates that a C. neoformans functional mutant of a GRASP orthologue had attenuated virulence in an animal model of cryptococcosis, in comparison with wild‐type (WT) and reconstituted cells. Mutant cells manifested altered Golgi morphology, failed to produce typical polysaccharide capsules and showed a reduced ability to secrete GXM both in vitro and during animal infection. Isolation of GXM from cultures of WT, reconstituted or mutant strains revealed that the GRASP orthologue mutant produced polysaccharides with reduced dimensions. The mutant was also more efficiently associated to and killed by macrophages than WT and reconstituted cells. These results demonstrate that GRASP, a protein involved in unconventional protein secretion, is also required for polysaccharide secretion and virulence in C. neoformans.

Phase behavior of olive and soybean oils in compressed propane and n-butane

Abstract - The aim of this work is to report the experimental data and thermodynamic modeling of phase equilibrium of binary systems containing soybean and olive oils with propane and n-butane. Phase equilibrium experiments were carried out using the static synthetic method in a high-pressure variable-volume view cell in the temperature range from 30 to 70 o C and varying the solvent overall composition from 5 to 98 wt%. Vapor-liquid, liquid-liquid and vapor-liquid-liquid phase transitions were observed at relatively low pressures. The Peng-Robinson and the SAFT equations of state without any binary interaction parameters were employed in an attempt at representing the phase behavior of the systems. Results show the satisfactory performance of SAFT-EoS in predicting qualitatively all phase transitions reported in this work. Keywords : Vapor-liquid equilibria; Liquid-liquid equilibria; Triglycerides; Propane; N-butane. INTRODUCTION Triglycerides and their fatty acid esters are important raw materials in many industrial processes. Their transformation provides products with high market values such as monoglycerides, widely used as emulsifiers in the food, cosmetics and pharmaceutical industries (Schmid, 1987; Ranalli and Mattia, 1997; Shiomori et al., 1995; Bhaskar et al., 1993). Furthermore, the transesterification of oil and fats produces a mixture of esters known as biodiesel. Such products have attracted considerable environmental interest in the past few years, mainly due to the low levels of pollutant emitted by user engines. Generally, the oil transformation in industrial scale is commonly accomplished by an acid or base-catalyzed reaction. However, yields reported as well as the quality of the products are usually low (Al Saadi and Jeffreys, 1981). An alternative process for obtaining products of high-grade quality is the use of enzyme-catalyzed reactions in supercritical or compressed solvents. Numerous studies have shown that many reactions can be conducted in compressed liquid or supercritical solvent and, in some cases, rates and selectivities achieved are greater than those obtained in normal liquid or gas phase reactions (Rendon et al., 2001; Oliveira and Oliveira, 2000; Jackson and King, 1997; Savage et al., 1995; King et al., 1987). To conduct such reactions, knowledge of the phase behavior of all components in the compressed solvent is of primary importance for process design optimization and for preventing enzyme inactivation due to the effects of high pressure.

Kinetics of Solvent-Free Lipase-Catalyzed Glycerolysis of Olive Oil in Surfactant System

This work reports experimental data and kinetic modeling of solvent-free glycerolysis of olive oil using a commercial immobilized lipase (Novozym 435) in the presence of Triton X-100 surfactant for the production of monoacylglycerols (MAG) and diacylglycerols (DAG). The experiments were performed in batch mode evaluating the effects of temperature (30-70 degrees C), enzyme concentration (2.5-18 wt %), Triton X-100 concentration (10-20 wt %), and glycerol to oil molar ratio (3:1, 6:1, and 9:1). Experimental results showed that lipase-catalyzed solvent-free glycerolysis with the addition of Triton X-100 might be a potential alternative route to conventional organic solvent methods, as good conversions were obtained with relatively low enzyme concentrations (9 wt %) in short reaction times (240 min). The glycerolysis and hydrolysis parallel reactions were considered with rate constants estimated by minimizing a maximum likelihood function. A very satisfactory agreement between experimental data and model results was obtained, thus allowing a better understanding of the reaction kinetics.

Enzymatic synthesis of ascorbyl palmitate in ultrasound-assisted system: Process optimization and kinetic evaluation

This work is focused on the optimization of reaction parameters for the synthesis of ascorbyl palmitate catalyzed by Candida antarctica lipase in different organic solvents under ultrasound irradiation. The sequential strategy of experimental design proved to be useful in determining the optimal conditions for reaction conversion in tert-butanol system using Novozym 435 as catalyst. The optimum production was achieved at 70°C, ascorbic acid to palmitic acid molar ratio of 1:9, enzyme concentration of 5 wt% at 3h of reaction, resulting in an ascorbyl palmitate conversion of about 27%. Reaction kinetics for ascorbyl palmitate production in ultrasound device showed that satisfactory reaction conversions (∼26%) could be achieved in short reaction times (2h). The empirical kinetic model proposed is able to satisfactorily represent and predict the experimental data.