Bioethanol Production from UK Seaweeds: Investigating Variable Pre-treatment and Enzyme Hydrolysis Parameters

Abstract This study describes the method development for bioethanol production from three species of seaweed.Laminaria digitata,Ulva lactucaand for the first timeDilsea carnosawere used as representatives of brown, green and red species of seaweed, respectively. Acid thermo-chemical and entirely aqueous (water) based pre-treatments were evaluated, using a range of sulphuric acid concentrations (0.125–2.5 M) and solids loading contents (5–25 % [w/v]; biomass: reactant) and different reaction times (5–30 min), with the aim of maximising the release of glucose following enzyme hydrolysis. A pre-treatment step for each of the three seaweeds was required and pre-treatment conditions were found to be specific to each seaweed species.Dilsea carnosaandU. lactucawere more suited with an aqueous (water-based) pre-treatment (yielding 125.0 and 360.0 mg of glucose/g of pre-treated seaweed, respectively), yet interestingly non pre-treatedD. carnosayielded 106.4 g g−1glucose.Laminaria digitatarequired a dilute acid thermo-chemical pre-treatment in order to liberate maximal glucose yields (218.9 mg glucose/g pre-treated seaweed). Fermentations withS. cerevisiaeNCYC2592 of the generated hydrolysates gave ethanol yields of 5.4 g L−1, 7.8 g L−1and 3.2 g L−1fromD. carnosa,U. lactucaandL. digitata, respectively. This study highlighted that entirely aqueous based pre-treatments are effective for seaweed biomass, yet bioethanol production alone may not make such bio-processes economically viable at large scale.