Influence of temperature on the anaerobic acidification of glucose in a mixed culture forming part of a two-stage digestion process

Abstract Using a Continuous Flow Stirred Tank Reactor inoculated with activated sludge, the anaerobic acidification of a 1% glucose monohydrate containing medium, allowing carbon limited growth of microorganisms, was studied with respect to maximum dilution rate and product distribution, over the temperature range from 20 to 60°C. A mesophilic and a thermophilic region could be distinguished, with optimum temperatures of 37°C (Dmax = 0.51 h−1) and 52°C (Dmax = 0.71 h−1) respectively. Optimal sludge loadings were, respectively, 77 and 112 kg COD (kg dw)−1 day−1. The gas phase consisted of carbon dioxide and hydrogen, and yield values ranged between 13.5–18.0% as the temperature was varied from 25 to 55°C. Deviations were obtained at lower and higher temperatures. In the liquid phase, mainly acetate, propionate, butyrate, lactate and ethanol were found. Precise description, in terms of carbon mass, C1 and oxidation/reduction balances, is presented. Product distribution at the maximum loading rates was fairly constant in the mesophilic range but is markedly variable in the thermophilic range. Product distribution also was highly dependent on sludge loading except at high loadings. Separate acidification should be designed at mesophilic temperature below optimal temperature and at high, almost maximal, sludge loadings.