Enzymatic Hydrolysis of Ascophyllum nodosum for the Co-Production of Biofuels and Value-Added Products

Abstract

There has been an increasing interest in the use of biorefining feedstocks for the production of value-added products. Seaweeds are of special interest, due to the fact that they do not compete for land use with food crops, have low to no lignin content, and can be grown in waste water or at sea, thereby using resources that are currently of low value. However, seaweed does have shortcomings, the most important being that seaweed has not been thoroughly studied as is the case for lignocellulosic materials. Canada has a large amount of coastline, and therefore, also has an abundance of algae. The collaborators at Acadian Seaplants Ltd. produce and sell a plant biostimulant from Ascophyllum nodosum, a brown algae. However, their production process results in the generation of large amounts of byproduct seaweed residues that have a highly basic pH and thus have very little current value. The primary objective of this work was to study the incorporation of enzymes to facilitate release of plant biostimulants from Ascophyllum nodosum, while simultaneously producing an algal biomass byproduct stream rich in sugars and at a pH that that is more amenable to downstream processing applications. Characterization of the seaweed sample was performed, and then proceeded with the enzymatic hydrolysis. For these experiments, well-known and commercially relevant cellulase enzyme blends were used, Celluclast® 1.5L, Cellic CTec2, and Viscozyme® L, as well as a commercial alginate lyase. A maximum of 70 ± 9% of the glucose present was released by the most successful enzyme treatment. To test for the presence of plant biostimulant activity in the enzyme hydrolysates, samples were sent for a mung bean rooting assay which was also performed. The rooting assays showed that the liquid hydrolysates had increased rooting activity when compared to the controls. The research presented in this thesis highlights the potential of using enzyme treatments to simultaneously produce a plant biostimulant and a sugar-rich byproduct stream that could be converted to value-added products through subsequent biorefining conversions.