抄録
The ecological role of sulface-reducing bacteria (SRB) in anaerobic degradation of a long-chain fatty acid (LFA) was investigated using three anaerobic sludge consorita cultivated at different sulfate loading rates. The three kinds of sludge (referred to as Sludge A, B and C) were cultivated in a fill-and-draw mode for 100 days by feeding with plamitate as a major carbon source (feeding concentration : 1.0g COD·l-1), but with different levels of sulfate, i.e., 600mg-SO42-·l-1 for Sludge A, 300 for Sludge B, 0 for Sludge C.
Degradation of palmitate into acetate in the presence of sulfate can be performed by either of the following three trophic groups : 1) symbiosis between palmitate-degrading proton-reducing acetogens (P-PRA) and hydrogen-utilizing SRB (H-SRB), 2) symbiosis between P-PRA and hydrogen-utilizing methanogens (H-MPB), 3) palmitate-oxidizing SRB (P-SRB). Three sludge consortia exhibited different behavior of palmitate degradation, depending on their sulfate loadings. As for Sludge A, the first group, P-PRA+H-SRB had the greatest contribution in palmitate degradation, and the extent of the second, P-PRA+H-MPB and the third, P-SRB were about half of the first, respectively. For Sludge B, P-PRA+H-MPB had the superior contribution over P-PRA+H-SRB and P-SRB. The lowest contributor, P-SRB was only one-tenth of the largest contributor, P-PRA+H-MPB. For Sludge C, palmitate degradation was accounted for only by P-PRA+H-MPB, and the contributions by P-PRA+H-MPB and P-SRB were negligible small.
