The energy conversion efficiency in hydrogen and methane cogeneration from Arthrospira maxima biomass by two-phase fermentation is improved with bacteria domestication and enzymatic hydrolysis. The A. maxima biomass (dried weight) can theoretically cogenerate hydrogen and methane yields of 318 ml/g and 262 ml/g, which dramatically increases the theoretical energy conversion efficiency from 16.6% in hydrogen only production to 61.9%. The experimental hydrogen yield is increased from 49.7 ml/g to 64.3 ml/g, when the hydrogenogens community is domesticated with A. maxima biomass as carbon source. The hydrogen yield is further increased to 78.7 mug when A. maxima biomass is hydrolyzed with glucoamylase, which gives an energy conversion efficiency of 4.1% in hydrogen only production. The soluble metabolite byproducts from the first hydrogen-producing phase are reutilized by methanogens to produce methane of 109.5-145.5 ml/g in the second phase. The cogeneration of hydrogen and methane from A. maxima biomass markedly increases the experimental energy conversion efficiency to 27.7%. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.