Attachment and growth of sulphate-reducing bacteria on different support materials

Attachment and growth of sulphate-reducing bacteria on different surfaces w as studied. A mixed culture of sulphate-reducing bacteria was grown autotro phically on a CO2/H-2 mixture in a defined medium in the presence of suppor t materials: polyurethane foam, lava rock and Ringlace(R), and encapsulated in alginate beads. Over a period of fourteen days, the quantities of bioma ss attached to the support particles and in suspension were determined by m easuring the total kjeldahl nitrogen (TKN) content of the respective attach ed and suspended portions. For the foam and the alginate beads, 73% and 84% , respectively, of the total biomass was attached to the support material a t the end of the fourteen days. For the Ringlace(R) and lava rock much less er amounts of biomass were attached to the supports. Scanning electron micr ographs showed that the cells adhered to the surface of the foam and formed aggregates in the porous cavities of the foam. These aggregates appeared t o be attached to the foam surface via strands of extrapolymeric substance. The cells encapsulated in the alginate beads grew preferentially in the cen tre of the bead. Some cells were seen growing in pockets on the surface of the lava rock particles. A few cells were very sparsely distributed on the surface of the Ringlace(R).