Patnaik, P R (2006) Neural network configurations for filtering of feed stream noise from oscillating continuous microbial fermentations. Bioautomation, 4. pp. 45-56. ISSN 1312 – 451X
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Abstract
Some microbial systems exhibit sustained oscillations under certain conditions. The maintenance and the suppression of oscillations are both important in different situations. While oscillations are clearly identifiable in small bioreactors, the influx of noise fuzzifies the oscillations in larger vessels. So, noise-filtering devices are employed to recover clear oscillating profiles. Recent work has shown that an auto-associative (AA) neural network is a better than standard algorithmic filters. In this study, nine neural network designs are compared for their ability to filter Gaussian noise in the substrate inflow rate of a continuous fermentation containing Saccharomyces cerevisiae. While the AA network is the best overall, specific performance criteria favor other designs. Thus the choice of a neural filter depends on the evaluation criterion, which is guided by the application.
| Item Type: | Article |
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| Additional Information: | OPEN ACCESS |
| Uncontrolled Keywords: | Microbial oscillations, Saccharomyces cerevisiae, Bioreactor, Noise inflow, Neural filters. Introduction Many microbial processes exhibit sustained oscillations over long durations. Under controlled conditions, clear oscillations are observable. In more realistic natural environments and production processes, however, the influx of noise obfuscates the intrinsic oscillations from the aberrations caused by noise. Since the occurrence of oscillations is linked to the reactions inside the cells and to transport processes across the cell walls [22], the identification of the oscillating signals is important for the understanding and control of large bioreactors [6, 15, 34]. The bacterium Zymomonas mobilis and the yeast Saccharomyces cerevisiae have been the work-horses of most studies of oscillating phenomena. S. cerevisiae is more popular in view of its ease of cultivation, well-understood physiology and industrial importance [7, 22]. Two recent publications [23, 24] have addressed the issue of recovering smooth oscillations from noise-distorted concentration profiles during continuous fermentations with S. cerevisiae. Both studies were based on experimental observations [1, 7, 16, 27] that, in certain ranges of the dilution rate and the gas-liquid mass transfer rate of oxygen, continuous cultures of S. cerevisiae display oscillating profiles for some key concentrations such as those of the biomass, carbon substrate (glucose), product (ethanol), storage carbohydrate and dissolved oxygen. Different types of oscillations occur in different ranges of these two manipulated variables, and some oscillations may comprise a superposition of two or more simple unimodal oscillations of different amplitudes. |
| Subjects: | Q Science > QR Microbiology |
| Depositing User: | Dr. K.P.S.Sengar |
| Date Deposited: | 17 Feb 2012 16:43 |
| Last Modified: | 17 Feb 2012 16:43 |
| URI: | http://crdd.osdd.net/open/id/eprint/1029 |
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