Microwave-assisted alkali pretreatment of rice straw to promote enzymatic hydrolysis and hydrogen production in dark- and photo-fermentation

Abstract

Rice straw was pretreated by microwave-assisted alkali to improve saccharification in enzymatic hydrolysis and hydrogen yield in combined dark- and photo-fermentation in this paper. A maximum reducing sugar yield of 69.3g/100gTVS was obtained when 50g/l rice straw was pretreated by microwave heating for 15min at 140°C in 0.5% NaOH solution and then enzymatically hydrolyzed for 96h. When hydrolyzed rice straw was used for hydrogen production by anaerobic bacteria in dark-fermentation, a maximum hydrogen yield of 155ml/gTVS was obtained. The residual solution (mainly acetate and butyrate) from dark-fermentation was reutilized for hydrogen production by immobilized photosynthetic bacteria in photo-fermentation. By combination of dark- and photo-fermentation, the maximum hydrogen yield was greatly enhanced to 463ml/gTVS, which is 43.2% of the theoretical hydrogen yield.