No abstract

No abstract

No abstract

Kluyveromycea bdgaricus cells were immobilized in matrices resisting to complexing anions. Yeast entrapped in alginate stabilized by polyethylenimine and glutaraldehyde were unable to hydrolyse whey owing to the inactivation of B-galactosidase by the stabilizing agents. Chitosan was resistant to whey medium but decreased the yeast hydrolyzing capacity by 15% with respect to alginate. The hydrolysis rate was found to be unchanged,for 37 days at 21--25°C.Kluyveromyces bulgaricus cells have been immobilized in calcium alginate beads and used to hydrolyse efficiently whey permeate [l]. During our experiments we have observed that the flow of whey through the alginate column induced an increase in the diameter of the beads which slowly lost their firmness. This well known phenomenon which becomes prominent as the temperature raises, is brought about by the presence of coniplexing anions in whey such as phosphate and citrate. This drawback could be overcome by adding calcium ions (10-20 mM) into the medium [2-41. Unfortunately, supplementation of calcium chloride in sterilized whey permeate resulted in a significant decrease of pH (pH 5.6), low enough to inactivate the cell /I-galactosidase activity [5].The selected strnin (Kluyveronyccs bdguricvs IRC 101) waa grown in a whey permeate medium (pR 7) on a gyratory shaker for 16 hours at 25OC which corresponds to the mid -logarithmic growth phase. The cells were harvested by centrifugation, washed twice with water, permeabilized by aqueous alcohol solution [6] treated withglutaraldehyde [7] and washed thoroughly with 10 mM phosphate buffer pH 7. Determination of /I-qa&wtosidase BctivityCells in suspension, after biomasa estimation a t 600 nm, were mixed with ONPG solution (o-nitrophenyl-B-galactopyranoside) a t 3OoC and the release o-nitrophenol was followed according to the method described previously [8]. Dry weight of the suspension was determined by drying an aliquot a t 105OC for 4 h.

No abstract