| Summary: | The removal of multiple substrates in a defined mixed culture process was investigated in the treatment of brewery wastewater. The study was conducted using both batch and a semi-continuous reactor system called self-cycling fermentation. Batch experiments were conducted using a synthetic brewery wastewater containing glucose, ethanol and maltose. Activated sludge from a municipal wastewater treatment plant was acclimatized in the synthetic brewery wastewater. The microbes capable of degrading this wastewater were analyzed by a combination of microscopy, spread plating, and Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) and identified as Acinetobacter sp., Enterobacter sp. and Candida sp. From the pure culture batch experiments, it was determined that Enterobacter could degrade glucose and maltose but no ethanol, while Acinetobacter and Candida could degrade all three carbon sources. In mixed culture batch experiments, Enterobacter was dominant in degrading the sugar concentrations to levels permissible for Acinetobacter to degrade ethanol. PCR-DGGE was found to be effective in identifying the dominant species but selective carbon source plating was required to determine viability and track the population dynamics. Kinetic experiments were carried out in a semi-continuous, self-cycling fermentation process using the defined mixed culture in media containing glucose and various initial concentrations of ethanol and maltose. The overall rate of substrate removal was attributable to both the suspended culture and the biofilm formed during the process. A rate expression was developed for this system for the range of substrate concentrations tested. The data indicated that substrate removal by the suspended culture was a function of only the biomass concentration. However, substrate removal by the biofilm was found to be limited to the surface cells and determined to be a function of substrate concentration only.
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