Enzymatic hydrolysis of the industrial solid residue of red seaweed after agar extraction: Extracts characterization and modelling

Abstract

The efficiency of enzymatic hydrolysis for the release of different biocompounds such as total phenolic compounds (TPC), sugars and proteins from the industrial solid residue of G. sesquipedale after agar extraction has been evaluated. Cellulase (0.25–8%, w/w, enzyme: solid residue, pH = 5) has been proved to be an efficient enzyme to degrade the algae cell wall improving the release of the bound TPC with values up to 7.5 mg gallic acid equivalent/g dry macroalgae residue. Monomer and oligomer carbohydrates were released to the reaction medium, namely glucose, galactose and arabinose with higher yields by increasing cellulase concentration. Enzyme combinations with other hydrolytic enzymes, such as xylanase and protease, did not bring any improvement of the TPC and sugar yields. Protein was also released to the enzymatic medium with protein extraction yields around 30%. The use of protease under basic conditions led to an increase in the release of the protein fraction and of the free amino acids content with a hydrophobic ratio higher than in the raw material. The kinetics of TPC and protein hydrolysis have been fitted to the power law and the Weibull models yielding the Weibull model the best fitting quality.