A NOVEL RECYCLE BATCH IMMOBILIZED CELL BIOREACTOR FOR PROPIONATE PRODUCTION FROM WHEY LACTOSE

Recycle batch fermentations using immobilized cells of Propionibacteri um acidipropionici were studied for propionate production from whey pe rmeate, de-lactose whey permeate, and acid whey. Cells were immobilize d in a spirally wound fibrous sheet packed in a 0.5-L column reactor, which was connected to a 5-L stirred tank batch fermenter with recircu lation. The immobilized cells bioreactor served as a breeder for these recycle batch fermentations. High fermentation rates and conversions were obtained with these whey media without nutrient supplementation. It took similar to 55 h to ferment whey permeate containing similar to 45 g/L lactose to similar to 20 g/L propionic acid. Higher propionate concentrations can be produced with various concentrated whey media c ontaining more lactose. The highest propionic acid concentration obtai ned with the recycle batch reactor was 65 g/L, which is much higher th an the normal maximum concentration of 35 to 45 g/L reported in the li terature. The volumetric productivity ranged from 0.22 g/L h to 0.47 g /L h, depending on the propionate concentration and whey medium used. The corresponding specific cell productivity was 0.033 to 0.07 g/L g c ell. The productivity increased to 0.68 g/L h when whey permeate was s upplemented with 1% (w/v) yeast extract. Compared with conventional ba tch fermentation, the recycle batch fermentation with the immobilized cell bioreactor allows faster fermentation, produces a higher concentr ation of product, and can be run continually without significant downt ime. The process also produced similar fermentation results with nonst erile whey media. (C) 1995 John Wiley and Sons, Inc.