Biotechnology and Bioengineering, Vol.100, No.5, 855-863, 2008
Enhancement of biogenic sulfide production in a packed-bad bioreactor via critical inoculum design and carrier material selection
Sulfate reducing bacteria (SRB) are commonly used in environmental bioprocesses for the treatment of acid mine drainage and sulfate wastewaters. Biogenic H2S is also a potential source of H-2 fuel with the recent development of H2S splitting technologies. In this study, a sulfate reducing packed bed bioreactor (PBR) capable of rapidly achieving high volumetric productivities was developed using a novel method of rational inoculum design and the selection of improved biomass carrier materials. An inoculum with initial composition of similar to 95% Desulfovibrio desulfuricans (ATCC 7757) and 5% SRB consortium was designed based on the pure strain's superior immobilization potential and the SRB consortium's superior kinetics. Diatomaceous earth (DE) pellets, porous glass beads, polyurethane foam and bone char were evaluated as potential biomass carrier materials. The DE pellets immobilized the most biomass and were employed in two packed bed bioreactor fermentations. Using the designed inoculum and DE pellets, a packed bed bioreactor achieved a volumetric productivity of 493 mol H2Sm-3 day(-1) (based on a 308 mL working volume) with a dissolved sulfide concentration of 9.9 mM. This occurred after 8.3 days of operation and represents a tenfold reduction in the start-up period compared to other sulfate reducing PBRs described in the literature.