Ethanol production from marine algal hydrolysates using Escherichia coli KO11

► Acid- and hydrolytic enzyme-treatments of 4 algae produced fermentable sugars at different composition and ratios. ► Laminaria japonica hydrolysate contained a high amount of mannitol. ► Escherichia coli KO11 efficiently fermented mannitol as well as a mixture of mannitol and glucose in hydrolysate. ► E. coli KO11 and hydrolytic enzymes could be used for simultaneous saccharification and ethanol fermentation of L. japonica with high mannitol content. Algae biomass is a potential raw material for the production of biofuels and other chemicals. In this study, biomass of the marine algae, Ulva lactuca, Gelidium amansii, Laminaria japonica, and Sargassum fulvellum, was treated with acid and commercially available hydrolytic enzymes. The hydrolysates contained glucose, mannose, galactose, and mannitol, among other sugars, at different ratios. The Laminaria japonica hydrolysate contained up to 30.5% mannitol and 6.98% glucose in the hydrolysate solids. Ethanogenic recombinant Escherichia coli KO11 was able to utilize both mannitol and glucose and produced 0.4 g ethanol per g of carbohydrate when cultured in L. japonica hydrolysate supplemented with Luria–Bertani medium and hydrolytic enzymes. The strategy of acid hydrolysis followed by simultaneous enzyme treatment and inoculation with E. coli KO11 could be a viable strategy to produce ethanol from marine alga biomass.