Laminaria digitata as a potential carbon source for succinic acid and bioenergy production in a biorefinery perspective

A novel biorefinery concept utilizing macroalgae Laminaria digitata to produce succinic acid, and direct the process residues for feed and energy production, is investigated in the present study. Enzymatic hydrolysis was performed at high solid loading (25%wv^-1) resulting in solubilization of the carbohydrates to soluble sugars, which accumulated in the liquid hydrolysate. The overall sugar recovery in the macroalgae hydrolysate was 78.23%. Actinobacillus succinogenes 130Z was able to ferment macroalgae hydrolysate to succinic acid with a yield of 86.49% (gg^-1 of total sugars) and an overall productivity of 0.50gL^-1h^-1. Removal of carbohydrates from the macroalgal biomass through enzymatic hydrolysis resulted in up-concentration of protein and lipid fractions in the post-hydrolysis solid residue (PHSR). Energy recovery of PHSR and fermentation broth through anaerobic digestion corresponded to 298 and 285NmLCH₄g^-1 VS_added, respectively. PHSR could potentially be used for: dietary food additive, fish feed, bioenergy production and added value products. This study opens possibility to conceive different biorefinery scenarios in which the efficient use of the macroalgal biomass fractions can provide numerous added-value bio-based products and energy.