Mass transfer coefficient evaluation for pilot scale fermenter using sodium sulphite oxidation method

Author(s): Rajesh Ghosh*, Sounak Bhattacherjee

Abstract

An adequate supply of oxygen in aqueous solution becomes the focal point of interest when it comes to the growth and maintenance of most aerobic microbial and tissue cultures used for biochemical and pharmaceutical production. Unfortunately, oxygen mass transfer to the growth medium serves as a major growth limiting factor owing to it’s low solubility in aqueous solutions. (Approximately 10 ppm at ambient temperature and pressure). The reaction rate is such that as oxygen enters the liquid phase, it is immediately consumed to oxidize the sulfite so that the rate of oxidation equals that of the oxygen transfer. Oxygen must at first be transferred from gas bulk through a series of steps onto the surfaces of cells before it can be utilized. Therefore the enhancement of gas-liquid mass transfer during aerobic cultures and fermentations is always put into priority. The present study involves using the ‘Central Composite Design’, a statistical technique to determine the parametric conditions for the optimum volumetric mass transfer coefficient in a pilot scale (40L) fermenter. The optimum volumetric mass transfer coefficient was found to lie outside the range of parameters studied and analytical expressions was obtained to predict the volumetric mass transfer coefficients for the parameter ranges studied using response surface methodology. The analytical expression was addressed to be significantly valid based on ANOVA results.

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