Combination of hydrogen fermentation and methanogenesis to enhance energy conversion efficiency from trehalose

• Trehalose was microwaved with dilute acid to improve glucose yield.
• Hydrolyzed trehalose was fermented by hydrogenogens to improve dark H2 yield.
• H2 yield from trehalose was markedly enhanced by dark- and photo-fermentation.
• Cogeneration of H2 and CH4 increased energy conversion efficiency.

Trehalose was pretreated by microwave heating with dilute acid to improve glucose yield and hydrogen production during dark-fermentation. An optimal glucose yield of 0.95 ± 0.08 g/g-trehalose was obtained when trehalose was pretreated by microwave heating with 1% dilute H2SO4 for 25 min at 120 °C. The hydrolyzed trehalose was inoculated with HPB (hydrogen-producing bacteria) to produce hydrogen during dark-fermentation. The residual solution of dark-fermentation was reused by PSB (photosynthetic bacteria) during photo-fermentation. The residual solution of photo-fermentation was reused by MPB (methane-producing bacteria) during methanogenesis. The maximum yields of hydrogen and methane were 731.3 ± 33.6 ml/g-trehalose and 116.9 ± 4.3 ml/g-trehalose. The sequential generation of hydrogen and methane from trehalose remarkably enhanced the energy conversion efficiency from 47.2 ± 2.2% in hydrogen fermentation to 72.2 ± 3.1% in combined hydrogen fermentation and methanogenesis.