lThe biofilm technique has been proved to be an effective cell immobilization method for wastewater biodegradation but it has had restricted use in the field of photobiological H(2) production. In the present study, a groove-type photobioreactor was developed and it was shown that a groove structure with large specific surface area was beneficial to cell immobilization and biofilm formation of the photosynthetic bacteria on photobioreactor surface as well as light penetration. A series of experiments was carried out on continuous hydrogen production in the groove-type photobioreactor illuminated by monochromatic LED lights and the performance was investigated. The effects of light wavelength, light intensity, inlet glucose concentration, flow rate and initial substrate pH were studied and the results were compared with those obtained in a flat panel photobioreactor. The experimental results show that the optimum operational conditions for hydrogen production in the groove-type photobioreactor were: inlet glucose concentration 10 g/L, flow rate 60 mL/h, light intensity 6.75 W/m(2), light wavelength 590 nm and initial substrate pH 7.0. The maximum hydrogen production rate, H(2) yield and light conversion efficiency in the groove-type photobioreactor were 3.816 mmol/m(2)/h, 0.75 molH(2)/molglucose and 3.8%, respectively, which were about 75% higher than those in the flat panel photobioreactor. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.