Structured model of bacterial growth and tests with activated sludge in a one-stage and two-stage chemostat

A kinetic model for a growing culture of micro-organisms was developed that correlated the biochemical structure of cells with quantitative physiological behaviour. The three-compartment model was adequate for simulation of continuous, batch and transient experiments with activated sludge fed on vanillin. The model assumed three basic compartments in a cell: (1) a building-block for synthesis of energy-rich compounds, small metabolites, DNA and storage materials; (2) the protein-synthesizing machinery; (3) the pool of enzymes and other proteins. The concept of viability was incorporated by postulating irreversible conversions of the three compartments to inert fractions.<p/>The two-stage activated-sludge process was improved and a mathematical model was developed for kinetic optimalization of the process. The two-stage process was better than the one-stage process in rate of vanillin breakdown. The kinetic coefficients of the second stage were affected by concentration and composition of intermediate substrate. Increase of maximum yield coefficient and simultaneous decrease of maintenance coefficient of the second stage with decreasing concentration of intermediate substrate were predicted by fitting the biochemical data of the second stage to the model. The production of biomass in the two-stage system under optimum kinetics was always greater than that of the one-stage system. The presence of acetate allowed higher rates at low concentrations of substrate, reducing the kinetic' advantage of the two-stage process.<p/>The predominant populations of bacteria in the chemostat altered if the specific growth rate was increased by a factor 4 or when acetate was added to the vanillin-basal medium. Much of the sludge flocs were built up by fibrillar cellulose-like exopolymers and may play an essential role in the mechanism of flocculation.

Bibliographic Details

Main Author:	Harder, A.
Other Authors:	Fohr, P.G.
Format:	Doctoral thesis biblioteca
Language:	English
Published:	Pudoc
Subjects:	biological treatment, waste water treatment, water treatment, afvalwaterbehandeling, biologische behandeling, waterzuivering,
Online Access:	https://research.wur.nl/en/publications/structured-model-of-bacterial-growth-and-tests-with-activated-slu
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