Andrea Lopes de Oliveira Ferreira

Immobilization of Candida antarctica Lipase B by Covalent Attachment to Green Coconut Fiber

The objective of this study was to covalently immobilize Candida antarctica type B lipase (CALB) onto silanized green coconut fibers. Variables known to control the number of bonds between enzyme and support were evaluated including contact time, pH, and final reduction with sodium borohydride. Optimal conditions for lipase immobilization were found to be 2 h incubation at both pH 7.0 and 10.0. Thermal stability studies at 60°C showed that the immobilized lipase prepared at pH 10.0 (CALB-10) was 363-fold more stable than the soluble enzyme and 5.4-fold more stable than the biocatalyst prepared at pH 7.0 (CALB-7). CALB-7 was found to have higher specific activity and better stability when stored at 5°C. When sodium borohydride was used as reducing agent on CALB-10 there were no improvement in storage stability and at 60°C stability was reduced for both CALB-7 and CALB-10.

Simulation and Optimization of Biodiesel Production by Soybean Oil Transesterification in Non-Ideal Continuous Stirred-Tank Reactor

This research examines the transesterification reaction of soybean oil with methanol in order to model and simulate a non-ideal continuous stirred-tank reactor. A mathematical model has been developed for the reactor. The biodiesel production process was optimized by application of factorial design 25 and response surface methodology. Factorial design and response surface analysis were combined with modeling and simulation to determine the operating conditions that maximize biodiesel production and minimize reactor volume. The optimum results obtained were conversion (0.95), molar ratio alcohol/oil (6:1), temperature (60.5 oC), ? (0.75), bypass (0.10) and reactor volume (1,500 L).

Simulation of Process Interesterification in Fluidized Bed Bioreactor for Production of Biodiesel

Abstract The aim this work was investigated a new route for biodiesel production using immobilized lipase from Candida antarctica in continuous Fluidized Bed Bioreactor. Conventionally, Biodiesel (fatty acid methyl esters) is produced by transesterification in which, oil or fat is reacted with a monohydric alcohol in presence of a catalyst. In recent years, the use of lipases as biocatalysts for biodiesel production has become of great interest due to its environment friendly. But some alcohols such as methanol inactivated the lipases to some extent and the enzymatic stability was poor. In order to enhance the stability of the lipase, three-step methanolysis was adopted, however, glycerol, as one of the products was easy to adsorb on the surface of lipase resulting in serious negative effect on the enzymatic activity. For to solve problems was used the interesterification kinetics of triglycerides and methyl acetate for biodiesel production was modeled. A heterogeneous model describing the interesterification process in an immobilized enzyme fluidized-bed bioreactor was developed. A simplified model based on Ping Pong Bi Bi with substrate competitive inhibition mechanism was proposed to describe the reaction kinetics of the interesterification. The model without any adjustable parameters was used to predict the interesterification process. The key parameters which measured the extent of external and internal mass-transport resistances, as well as the degree of back-mixing were quantified and discussed. The fluidized-bed bioreactor considered in this investigation is composed of two phases: a fluid phase comprised mainly of the triglycerides and methyl acetate and the product (Biodiesel); and a solid phase which is the immobilized enzyme. The effects of some operating and design parameters on the performance of the fluidized-bed bioreactor were also analyzed. The model was also tested for its sensitivity to changes in hydrodynamic parameters.

The Kinetics of Ampicillin Release from Hydroxyapatite for Bones Regeneration

Semisynthetic beta-lactam antibiotics are among the most used pharmaceuticals. Their use in veterinary and human medicine is in continuous expansion. There is a growing need for developing bioactive implants. Advantages of implantable drug delivery tools can include high release efficiency, precise dose control, low toxicity, and allow to overcome disadvantages connected with conventional methods. In this respect, hydroxyapatite (HA) is an elective material. It enables to produce architectures similar to those of real bones. Here we studied a kinetic model to describe ampicillin release from HA. In the course of adsorption experiment, ampicillin was dissolved, maintained at 30∘C and shaken at 60 strokes/minute. Samples were withdrawn periodically for analysis and then returned to the mixture. Adsorbed amounts were measured by the difference of the concentration of the antibiotics before and after adsorption using UV adsorption at 225 nm. The aim of this work was to evaluate its application as ampicillin delivery carrier.

Macroporous Calcium Phosphate Bioceramics as Drug Release Agents: A Kinetics Study of Ampicillin Release

Semi-synthetic beta-lactam antibiotics are the most important class of antibacterial agents. Their use in veterinary and human medicine is in continuous expansion. Calcium phosphate bioceramics have been used in medicine and dentistry for nearly 30 years. Calcium phosphate ceramics (CPC) are nowadays being widely used as drug delivery systems because of their desirable properties such as biocompatibility, bioresorbability, controlled release etc. In recent years In this work, kinetic models to describe ampicillin adsorption from CPC were investigated. Calcium phosphate bioceramic are analogous to the mineral component of bones, its properties make it suitable for implant materials and delivery agents of drugs