It was the first time to study the enhancement effect of nanometer-sized gold particles on fermentative hydrogen production from artificial wastewater. A biohydrogen production system coupling the polysaccharide degradation by two cultures and hydrogen production using gold nanoparticles as a catalyst was investigated. Data were obtained from tests operating with cultures enriched from natural environment, which included preheat-treated mixed culture and non-heat-treated mixed culture. The percentages and yields of hydrogen produced in the tests using gold nanoparticles were all higher than the corresponding blank test. The tests with 5-nm-gold particles behaved better than others, especially for the preheat-treated one. The maximum cumulative yield of hydrogen obtained at the test with 5-nm-gold particles was 4.48 mol per mol sucrose, which represents the conversion efficiency of sucrose to hydrogen reached 56%. The results indicated that gold nanoparticles could remarkably improve the bioactivity of hydrogen-producing microbes and the enhancement effect strongly depended on the size of gold particles. This work suggests a promising method to enhance the catalytic activity of hydrogenases in the microbes and will be of great importance in biohydrogen production. (c) 2006 International Association for Hydrogen Energy.