Mechanisms and Kinetics of Succinate and Propionate Degradation in Anoxic Freshwater Sediments and Sewage Sludge

Abstract

SUMMARY: The interrelation of propionate and succinate metabolism in anoxic sewage sludge and in two different anoxic lake sediments was studied. The mechanism of propionate degradation and the kinetics of propionate and succinate metabolism were analysed using specifically labelled 14C tracers and gas chromatography-gas proportional counting techniques. The labels of [1-14C]propionate and [1,4-14C]succinate were transformed almost exclusively to carbon dioxide whereas the label of [3-14C]propionate was transformed to equal amounts of methane and carbon dioxide, indicating a randomizing pathway of propionate degradation. The pool sizes of propionate and succinate (0·3-2·3 μmoll-1) were similar to each other in, but were both different between, each of the three environments studied. The turnover times of succinate were shorter than those of propionate, and the C-1 label of propionate and the C-1 and C-4 labels of succinate were metabolized far faster than the respective C-3 and C-2 and C-3 labels. These results indicate that propionate, although formed via succinate, is also degraded via succinate in the anoxic environments studied, and that succinate metabolism is at least as important as propionate metabolism in anaerobic degradation processes.