Influence of anaerobic culture acclimation on the degradation kinetics of various substrates

The adaptation of an anaerobic culture (anaerobic sludge) to a specific sub strate brings significant changes to its microbial population. These change s can be described by the sludge's ability to treat various substrates such as carbohydrates or proteins or "intermediate" products of anaerobic metab olism such as L-lactic, propionic, and acetic acids. The activity of the sl udge with respect to a specific substrate is a critical parameter, because the anaerobic degradability of wastewaters depends strongly on it. This wor k examines and quantifies the differentiation of two anaerobic sludges of t he same origin, following an adaptation period of about 18 months to lactos e and gelatin, respectively. The acclimation has a significant effect on th e maximum specific utilization rates of various compounds and on their appa rent consumption kinetics. It is noticeable, however, that even if the anae robic cultures were not exposed to a specific substrate for a prolonged per iod of time (more than a year), they still kept the ability of hydrolyzing or degrading it. In addition, the acclimation has an unquestionable effect on the stoichiometry of the production of volatile fatty acids and L-lactat e. Finally, from codigestion experiments it is shown that codigestion of la ctose and gelatin appears to have no effect on their hydrolysis kinetics in any of the lactose or gelatin acclimated cultures; specifically, the hydro lysis kinetics remained the same as calculated when lactose or gelatin were the only fed substrates. Similarly, the kinetics of L-lactate and D-glucos e biodegradation seemed to be unchanged. On the other hand, codigestion has a significant effect on the production of L-lactic, propionic, and acetic acids, which can be attributed to the increased hydrogen production accompa nying gelatin biodegradation. (C) 2001 John Wiley & Sons, Inc.