FIG. 2.

Schematic drawing of the anaerobic filtration system. The crossflow filtration unit was equipped with five Durapore membranes (pore size, 0.2 μm; filter surface, 0.46 m²) (Millipore). The cells were kept in suspension and were pumped under pressure over the filter surface. Before filtration, the complete system was flushed for 10 min with CO₂ to remove oxygen. During the filtration procedure, a protective atmosphere of CO₂ was maintained to prevent cellular damage due to oxygen sensitivity, to prevent precipitation of inorganic compounds, and to keep the pH of the sample constant. The concentrated brine was collected in tank 1; tank 2 was for storage. Brine flowed into the filtration unit at valve 1, concentrated cells exited at valve 2, and the filtrate outflow was at valve 4. Valve 3 is a closed valve.