EXTRACELLULAR POLYSACCHARIDE PRODUCTION BY LACTOBACILLUS-DELBRUECKII SUBSP BULGARICUS RR IN A CONTINUOUS FERMENTOR

Fermentations utilizing lactic acid bacteria generally employ batch pr ocesses. Continuous fermentations may have advantages in that the accu mulation of lactic acid can be limited and fermentation equipment can be more efficiently utilized. Extracellular polysaccharide (EPS) of La ctobacillus delbrueckii subsp. bulgaricus RR was produced by continuou s fermentation. Partially deproteinized sweet whey supplemented with l actose, casamino acids and ammonium chloride sewed as the fermentation substrate. The effects of pH, dilution rate and nutrient levels on th e production of EPS were determined. EPS concentration increased with an increase in dilution rate. The highest concentration of EPS (2.13 g /L) was obtained at a dilution rate of 0.055 h(-1) and pH 6.5. At this dilution rate, fermenter productivity ranged from 0.03-0.11 g EPS/L h depending on the pH of the medium and the level of nutrient supplemen tation used. At a dilution rare of 0.028 h(-1), lactose utilization ra nged from 58-76%, while at a dilution rate of 0.055 h(-1) lactose util ization ranged from 23-65%. Fermenter productivity and EPS concentrati on decreased with a decrease in medium pH. At pH 6.5, fermentor produc tivity ranged from 0.073 to 0.11 g EPS/L h, while at pH 5.2, productiv ity ranged from 0.03-0.06 g EPS/L h. At pH 6.5, EPS concentration rang ed from 1.55 to 2.13 g/L and at pH 5.2 the concentration of EPS ranged from 0.6-1.06 g/L. Addition of casamino acids and NH4Cl increased EPS production.