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Hydrolysis of rice bran oil using an immobilized Lipase from Candida rugosa

Murty, Ramachandra V (2005) Hydrolysis of rice bran oil using an immobilized Lipase from Candida rugosa. Phd. Thesis thesis, Manipal Institute of Technology, Manipal.

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Abstract

The thesis deals with the enzymatic splitting of abundantly available raw material, rice bran oil into free fatty acids and glycerol in jacketed batch reactor and column reactor packed with immobilized lipase from Candida rugosa. Candida rugosa lipase has been immobilized by adsorption on acid washed glass beads. It was observed that lipase loading of the support depends on the size of the particle, with smaller particle containing higher amount of lipase per unit weight. 62 % of the original activity has been retained upon immobilization of lipase. Experiments on deactivation kinetics of immobilized lipase were performed in stirred batch reactor using rice bran oil as the substrate and temperature as the deactivation parameter. The data were fitted in first order deactivation model. The effect of temperature on deactivation rate was represented by Arrhenius equation. Initial reaction rate linearly varied up to enzyme concentration of 17.25 U/rnl. Amount of free fatty acids produced was linearly proportional up to the enzyme loading of 1650 ug/g of bead. Achievement of chemical equilibrium took longer time in the case of less lipase loading. Degree of hydrolysis was found to decrease in second and third consecutive batch operations on repeated use of immobilized lipase. The kinetics of enzymatic hydrolysis of rice bran oil in isooctane by immobilized lipase in a batch reactor showed competitive inhibition by isooctane with a dissociation constant, Kr , of 0.92 M. However, the batch reactor kinetics data obtained in the absence of isooctane followed the simple Michaelis-Menten kinetics with Ki m=0.2328 Mand Vi max=O.0281 Mlmin. External mass transfer effects during the hydrolysis of rice bran oil using immobilized lipase enzyme were studied in a differential recirculation reactor. Onset of external mass transfer limitations were found to be responsible for the optimum activity with respect to the enzyme loading. Particle size influences global reaction rate more at lower flow rates than at higher flow rates. Experiments performed in continuous immobilized lipase packed bed reactor to study the influence of substrate concentration and flow rate on fractional hydrolysis of rice bran oil showed that the apparent kinetic constants vary with flow rates. Experiments on the stability of emulsion in the continuous packed bed reactor showed an optimum flow rate of 8 ml/min with respect to fractional conversion. A recycle packed bed reactor has been used to increase the fractional conversion of rice bran oil. An optimum recycle ratio was determined as 9. The operational stability of the recycle reactor was estimated by continuously hydrolyzing the rice bran oil for 16 days. The operational stability was found to decrease in the presence of isooctane. The experimentally determined operational half-life of'Iipase was 360 h without isooctane but 288 h with 25% (v/v) isooctane in rice bran oil. The performance of an immobilized packed bed reactor for the hydrolysis of rice bran oil has been investigated and can be well described by: a dispersion model with average standard deviation of 0.0388. Global mass transfer coefficients estimated using the model and experimental data ranged from 0.095-0.482 min", depending on substrate flow rates. A dimensionless mass transfer correlation between the Sherwood number and the Reynolds number was obtained as NSh=3.96xNRe2 The reaction data were represented in dimensionless Eadie-Hofstee plot, which indicated the extent of film diffusion in packed bed reactor. Film effectiveness factor was calculated experimentally in the packed bed reactor and compared with the theoretically predicted values.

Item Type: Thesis (Phd. Thesis)
Uncontrolled Keywords: Batch reactor, Differential reactor, Deactivation kinetics, Dispersion model, Global mass transfer coefficients, Half-life, Immobilized lipase, Isooctane, Operational stability, Packed bed reactor, Rice bran oil, Recycle reactor, Mass transfer effects.
Subjects: Engineering > MIT Manipal > Chemical
Depositing User: MIT Library
Date Deposited: 29 May 2014 07:27
Last Modified: 07 Nov 2014 09:41
URI: http://eprints.manipal.edu/id/eprint/139592

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