Production of Concentrated Lactobacillus bulgaricus by Continuous Fermentation Coupled with Filtration

Author : Ramirez, Marife Valenzuela
Major Adviser : Chay, Pham Binh
Committee Members : Movillon, Jovita A.; Valencia, Sixto A.
Year : 1995
Month : March
Type : Thesis
Degree: BS
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Concentrated Lactobacillus bulgaricus  was produced by continuous fermentation coupled with filtration. A ceramic filter was incorporated to the system which separates the inhibitory metabolites and simultaneously recycling the cells in the fermentor.

The effect of the following on the biomass production was studied: dilution rate (0.05, 0.10 and 0.15 h⁻¹), lactose concentration (40, 60 and 90 g/L) and pH (5.0, 5.6 and 6.0). Eighteen randomly selected process conditions were tested.  Continuous fermentation was carried out for 48hours after 18 hours of batch fermentation. Multiple Linear Regression Analysis was done to determine the constants of the polynomial equation that describe the interaction among three process variables.

The biomass production decreased at increasing dilution rate. A parabolic response was observed on the biomass production as affected by both lactose concentration and pH considering other factors constant. Interaction effects between any two variables as well as among the three variables were present.

Using Response Surface Analysis, optimum biomass of 14 x 10¹¹ cells/mL was obtained at pH range of 5.25 to 5.72, lactose concentration range of 56.67 g/L to 62.92 g/L and dilution rate of 0.05 h⁻¹.

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