Enzymatic and organic acid pretreatment of seaweed: effect on reducing sugars production and on biogas inhibition

Seaweeds are a valuable feedstock in the production of biofuels such as biogas. In order to achieve higher conversion rates, the biomass requires a pretreatment step. However, the use of harsh conditions is detrimental to the environment and negatively affects the biochemical composition of the seaweed, lowering the yields of the products. In this study, Laminaria digitata and Saccharina latissima were pretreated with organic acids and enzymes. The extent of hydrolysis was evaluated by the concentration of reducing sugars (RS) released from the seaweed. Thereafter, the effect of pretreatments on biogas production from L. digitata was investigated in 120 ml batch reactors incubated at 35°C. Oxalic acid and the enzymatic preparation Cellulase (Sigma C9748) improved the recovery of RS. Pretreatments inhibited the anaerobic digestion process and only a 6% increase in biogas production was obtained when the biomass was subjected to a combination of 2.5% citric acid and Cellulase.