Oxygen Transfer for Scaling-up Process of Lysine Production

Author : Almendrala, Cecile Mendoza
Major Adviser : Chay, Pham Binh
Committee Members : Acda, Reynaldo I.; Movillon, Jovita L.
Year : 1992
Month : October
Type : Thesis
Degree: BS
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Oxygen transfer in the fermentation medium and in the fermentation of Corynebacterium glutamicum was studied in a 5L stirred tank bioreactor. Volumetric oxygen transfer coefficient, kLa, was determined using static method and dynamic method of gassing-out.

The static, method was used in determining the effect of glucose concentration, aeration rate and agitation speed on kLa in the fermentation medium and in obtaining a model of scale-up equation. It was found out that kLa decreases with an increase in glucose concentration while it increases with an increase in aeration rate. Initially, increasing agitation speed increases kia but only up to a certain point where a further increase in agitation speed caused a decrease in kLa.

Testing the actual cultivation process of Corynebacterium glutamicum for the production of lysine was done in a shake flask experiment and in 5L stirred tank bioreactor using dynamic method in determining kLa . In the shake experiment glucose concentration decreased from 129 to 30 g/L while lysine was increased from 1.55 to 5.2 g/L after 144 hrs. In the dynamic method, kLa and glucose concentration decreased from 70.0 to 37.5 g/L and _from 131.0 to 45.8 g/L respectively, while lysine and biomass was increased from 0.8 to 5.9 g/L and from 4.35 to 13.8 g/L respectively after 40 hrs.

By multiple linear regression, scale-up equation was obtained, defining the relationship of kLa with the agitation speed Ni and superficial gas velocity Vs, for 5L stirred tank bioreactor at 150 g/L glucose concentration, pH 7 and 30 °C. The equation derived may only be strictly applied to the condition in which it was developed. A study on how kLa is affected by other operating variables (e. g. glucose concentration, PH, Ni, Vs and T) is recommended to develop a more general scale-up equation.

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