TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Bioreactor: The circulation system includes a pump (preferably centrifugal pump). The directional flow in the bioreactor is an up-flow or down-flow direction. The bioreactor further comprises a container for holding a solution that affects pH. The pH is monitored with a pH controller.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The pH of the organic feed material is affected by selectively releasing the solution into the organic feed material (preferably the pH is affected by selectively releasing the solution into the organic feed material as the organic feed material passes through the pump).The organic feed material is heated to 60 - 100degreesC, and the hydrogen producing microorganisms metabolizing the organic feed material has an oxidation reduction potential (ORP) of -300 - -450 mV. EXAMPLE - An organic feed material e.g. grape juice solution was heated at 65degreesC to kill or deactivated the methanogens. The organic feed material was introduced into bioreactor, and the hydrogen producing microorganism was metabolized the sugars in the organic feed material.    The bioreactor was initially operated at pH of 4.0 and a flow rate of 2.5 ml/minute, resulting in a hydraulic retention time (HRT) of 13 h (0.55 d). This was equivalent to a dilution rate of 1.8 per day. After one week the bioreactors were at pH 4.0, the oxidation reduction potential (ORP) ranged from -300 - -450 mV, total gas production averaged 1.6 L/day and hydrogen production averaged 0.8 L/day.    The mean chemical oxygen demand (COD) of the organic feed material during this period was 4000 mg/L and the mean effluent COD was 2800 mg/L, for a reduction of 30%. After one week, the pH of bioreactors were increased by one half unit per day until the bioreactors were established at different pH levels of 4.0 - 6.5. During this process, one mole of glucose produced two moles of hydrogen gas and carbon dioxide, without subsequent conversion of hydrogen to methane by methanogens.    It was found that the optimum pH for gas production was 5.0 at 1.48 L hydrogen per day. This was equivalent to 0.75 volumetric units of hydrogen per unit of bioreactor volume per day.