Optimisation of cellulase-assisted extraction of laminarin from the brown seaweed Ecklonia maxima, using response surface methodology

The beta-glucan laminarin is a high-value compound well suited for the food and nutraceutical industries because of its multiple bioactivities. Enzyme-assisted-extraction (EAE) is a proposed laminarin extraction technology that may retain the laminarin bioactivity due to mild extraction conditions relative to conventional methods. The aim of the study was to optimise the extraction of laminarin from the South African kelp, Ecklonia maxima, using response surface methodology. The commercial cellulase Celluclast (R) was used to hydrolyse the seaweed material in the range of 0 to 4.0% (v/dw) enzyme-substrate ratio (ES), pH 3.0 to 6.0, and temperatures of 40 to 60 degrees C. Samples were taken at 1.5 h intervals over 6 h of hydrolysis and hydrolysate supernatant samples were analysed for solubilised yield (SY), and concentration of reducing sugars (RS) and laminarin (L). It was found that L was significantly influenced by linear and quadratic effects of pH and temperature, but not by ES over the experimental range. However, RS and SY showed a significant linear effect of the ES term. Comparisons to alternative carbohydrase extraction (Accellerase (R)) showed Celluclast (R) to perform similarly to Accellerase (R) in all responses. When compared to conventional dilute-acid thermal hydrolysis (DATH: pH 1.0 and 70 degrees C), enzymatic extraction methods were superior in releasing RS and increasing SY at 4.5 h of hydrolysis. However, conventional DATH was shown to be superior to enzymatic extraction methods in selective extraction of laminarin.