A glass made HTLB with an on-line dissolved methane detector was used for the experiments. A schematic diagram of the bioreactor is illustrated in Fig. 1. The HTLB consists of two long horizontal parts, short vertical downstream and upstream tubes, a top part (separator) which is placed right above the upper end of the downstream, a U-shape bend, a liquid pump, gas supply distributors and staticmechanical mixers for the comminution of the gases introduced into the fermentation liquid. The bioreactor was comprised of a single wall looped-glass tube with diameter of 0.03m, height of 0.4m and a length of 2.2m.