USE OF ENZYMATIC CELL-WALL DEGRADATION FOR IMPROVEMENT OF PROTEIN EXTRACTION FROM CHONDRUS-CRISPUS, GRACILARIA-VERRUCOSA AND PALMARIA-PALMATA

The effect of polysaccharidases (kappa-carrageenase, beta-agarase, xyl anase, cellulase) on the protein extraction from three rhodophytes has been studied. The kinetic parameters (apparent V-m, apparent K-m) and the optimum activity conditions (pH, temperature) of each enzyme were determined by using pure substrates. All the tested enzymes possess M ichaelis Menten mechanism with estimated substrate saturating concentr ations of 8 000 mg 1(-1) (carrageenan) for kappa-carrageenase, 8000 mg l(-1) (agar) for beta-agarase, 5000 mg l(-1) (xylane) for beta-xylana se and 6000 mg 1(-1) (carboxymethylcellulose) for cellulase. The optim um activity conditions are pH 6.5-6.8 at 45 degrees C for carrageenase , pH 6-6.5 at 55 degrees C for agarase, pH 5 at 55 degrees C for xylan ase and pH 3.8 at 50 degrees C for cellulase. Different alga/enzymes c ouples (kappa-carrageenase/Chondrus crispus, beta-agarase/Gracilaria v errucosa, beta-xylanase/Palmaria palmata) were tested under the optimu m activity conditions. Alga/cellulase + specific enzyme (e.g. Chondrus crispus/carrageenase + cellulase) systems were also studied at the op timum activity conditions of a specific enzyme (e.g. carageenase). The use of the only cellulase was also tested on each alga. Except for Pa lmaria palmata, the highest protein yields were observed with the proc edures using cellulase coupled with carrageenase or agarase for an inc ubation period limited to 2 h. The Chondrus crispus/carrageenase + cel lulase and Gracilaria verrucosa/agarase + cellulase systems gave ten-f old and three-fold improvements, respectively, in protein extraction y ield as compared to the enzyme-free blank procedure. The combined acti on of xylanase and cellulase on protein extraction from Palmaria palma ta does not significantly improve protein yield. The best overall prot ein yield for P. palmata is for P. palmata/xylanase with a 14-h incuba tion time. This study shows the interest in the use of a polysaccharid ase mixture for improving protein extractibility from certain rhodophy tes. This biotechnology approach, adapted from procedures for protopla st production or enzymatic liquefaction of higher plants, could be tes ted as an alternative method to obtain proteins from seaweeds of nutri tional interest.