Effect of enzymatic digestion on thallus degradation and extraction of hydrosoluble compounds from Grateloupia turuturu

The extraction of metabolites of industrial interest from seaweed tissue is difficult due to the presence of anionic polysaccharides in the cell walls. We studied enzymatic digestion of Grateloupia turuturu (Rhodophyta) to facilitate extraction of the desired metabolites from this seaweed. Four polysaccharidases (Onozuka R-10 cellulase, agarase, κ- and ι-carrageenases) were used alone and in combination. We studied the efficiency of the enzymatic process in degrading the seaweed thallus; we also investigated the effect of the enzymatic treatment on solubilization of R-phycoerythrin and reducing sugars. The best degradation conditions for Grateloupia thalli were obtained with cellulase alone (0.48 U ml-1), or with a combination of cellulase/κ-carrageenase. However, only the combination cellulase (0.08 U ml-1)/κ-carrageenase (0.01 U ml-1), or the individual enzymes [agarase or ι-carrageenase at low concentration (0.55 U ml-1 and 2.5×10-3 U ml-1)] improved solubilization of R-phycoerythrin compared to the control conditions. The simultaneous use of polysaccharidases enabled solubilization of a large quantity of reducing sugars (40 mg glu g-1 dw). Therefore, this condition appears suitable for the production of oligosaccharides. This result also confirms indirectly the presence of agar, cellulose, κ- and ι-carrageenans in the cell wall of Grateloupia turuturu.