A NOVEL MODEL FOR CONTINUOUS FERMENTATION PROCESS FOR WORCESTERSHIRE SAUCE PRODUCTION USING A TRICKLE-BED BIOREACTOR

The mass balances of sugar and ethanol were computed on the assumption that the trickle bed bioreactor used was a continuous-flow stirred-ta nk reactor (CSTR), and simulation of the steady ethanol concentration at various dilution rates was performed using a modified Contois equat ion. The equation proposed here represents the conventional Contois eq uation as a particular equation of the modified formula (m=1.0). The s tability of the continuous fermentation in the production of Worcester shire sauce was evaluated, and this process was kinetically analyzed u sing the modified Contois equation. Neither decrease in yeast activity nor clogging with growth yeasts was observed in the trickle bed biore actor with comb-shaped ceramic carriers during the fermentation period (about 6 months). From the results of the evaluation of mixing condit ions this bioreactor can be regarded as a combination of a plug Bow re actor (PFR) in the ceramic part, and a CSTR in the retention part. How ever, the trickle bed bioreactor could function as a CSTR having the s ame capacity as the actual volume of the retention part for the fermen tation contribution rate of each part of the bioreactor. The observed ethanol concentration and productivity at the steady states were almos t the same as the values calculated using the material balance equatio ns of the sugar concentration and the ethanol concentration in a CSTR and the modified Contois equation with m=6.0. Thus, the modified Conto is equation (m=6.0) has been proposed as a design equation for a ferme ntation process for Worcestershire sauce production. When the modified Contois equation was applied to an acetic acid fermentation process a nd a plant tissue culture the observed product concentrations at each dilution rate were similar to the calculated values. It has been prove d that the modified Contois equation is applicable not only to an alco hol fermentation process for Worcestershire sauce production but also to other fermentation processes and growth reactions.