A photobioreactor was constructed with porous glass as an immobilization matrix. The reactor was a rectangular glass chamber (inner dimensions : 125 x 50 x 2.5 mm) containing a porous glass sheet (125 x 50 x 0.5 mm) on which Rhodobacter sphaeroides RV was immobilized (11.2 mg dry wt./ml porous glass). The maximum rate of hydrogen evolution was 1.3 ml/h/ml porous glass. The conversion efficiency of succinate into hydrogen reached 75%. Stable and efficient hydrogen evolution continued for up to 40 d.