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

Abstract

The adaptation of an anaerobic culture (anaerobic sludge) to a specific substrate brings significant changes to its microbial population. These changes can be described by the sludge's ability to treat various substrates such as carbohydrates or proteins or "intermediate" products of anaerobic metabolism such as L-lactic, propionic, and acetic acids. The activity of the sludge with respect to a specific substrate is a critical parameter, because the anaerobic degradability of wastewaters depends strongly on it. This work examines and quantifies the differentiation of two anaerobic sludges of the same origin, following an adaptation period of about 18 months to lactose and gelatin, respectively. The acclimation has a significant effect on the maximum specific utilization rates of various compounds and on their apparent consumption kinetics. It is noticeable, however, that even if the anaerobic cultures were not exposed to a specific substrate for a prolonged period 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-lactate. Finally, from codigestion experiments it is shown that codigestion of lactose and gelatin appears to have no effect on their hydrolysis kinetics in any of the lactose or gelatin acclimated cultures; specifically, the hydrolysis kinetics remained the same as calculated when lactose or gelatin were the only fed substrates. Similarly, the kinetics of L-lactate and D-glucose 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 accompanying gelatin biodegradation.

Anaerobic treatment of dairy wastewaters: a review

“…It was previously reported that carbohydrates could suppress the synthesis of exopeptidases, a group of enzymes facilitating protein hydrolysis [29]. Anaerobic degradation of proteins and the effects of ammonia on this mechanism were recently investigated in detail [30][31][32][33][34][35]. Casein is the major protein in milk composition and in dairy effluents.…”

Thermal and enzymatic pretreatment of sludge containing phthalate esters prior to mesophilic anaerobic digestion

“…The GAMS modeling language was used to formulate the optimization problem. The leastsquares objective was to select the best kinetic parameter values so as to minimize the squared residuals between the experimentally measured and the respective predicted concentrations (Gavala and Lyberatos, 2001).…”

Biochemical, morphological, and yield responses of lady's finger plants to varying ratios of palm oil mill waste (decanter cake) application as a bio-fertilizer

“…Upon such effects, the culture may transform into a new one. Adapting anaerobic mixed culture on lignocellulosic substrates at low temperature may come at the expenses of fats-and protein-metabolizing microorganisms (Gavala and Lyberatos 2001;Gavala et al 1999;Guieysse et al 2001). Precisely, adaptation may induce a population shift from the substrate sensitive to the substrate tolerant microorganisms.…”

“…Moreover, the kinetics of the culture may change as well. Gavala and Lyberatos (2001) reported that adaptation affected the consumption and kinetics (the maximum specific utilization rate) of various compounds in the mixed anaerobic culture significantly. The adaptation affects the stoichiometry of the reactions which produce the volatile fatty acids during the acidogenesis and acetogenesis (Gavala and Lyberatos 2001).…”