This research investigated the effects of various dilute acid (HCl, H2SO4, HNO3, H3PO4) pretreatment on the solubilization of marine macroalgal biomass Gelidium amansii and subsequent hydrogen fermentation in a batch vials. The dry grounded biomass was hydrolyzed at temperature of 121 degrees C, solid/liquid (S/L) ratio of 5% (w/v), dilute acid concentration (1%) of various reagents, and reaction time of 30 min. The hydrolyzates obtained at these conditions were then fed to batch hydrogen fermentation. Results revealed that only H2SO4 pretreatment method had a significant effect on improvement of biohydrogen production from Gelidium amansii, whereas the other pretreatment conditions were even worse than the control experiment. Dilute sulfuric acid (1%) provided a maximum hydrogen production of 52 mL-H-2/g-dry biomass, whereas control experiment provided a hydrogen efficiency of 27 mL-H-2/g-dry biomass. The results showed that selection of appropriate pretreatment method is essential for enhanced hydrogen production from macroalgal biomass. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.