Marshall, Carolynne Therese; (1992) The design and implementation of comparative reasoning tools for fermentations. Doctoral thesis (Ph.D.), University College London.

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Abstract

The progress of a fermentation is usually assessed by visual comparison of the time profiles of the data with those from other batches or from a standard or model. In this work the comparative reasoning process was automated, thereby eliminating the problems caused by human inconsistencies and bias, and facilitating a more thorough usage of all available data. The comparative reasoning was extended to include non-numerical and single-value data. A relational data base structure was designed to record all batch sheet and descriptive data from any fermentation and to enable the comparison of these data from one batch to another. The quantitative time variant data from two fermentations may be dissimilar in a strict numerical sense but may exhibit similar patterns or trends. Conventional numerical techniques cannot be used to detect these similarities. A graphical analysis process was developed to enable detection of periods of approximate similarity in two time profiles: the data were simplified by segmentation into linear episodes, described qualitatively using the descriptive language of an expert, and algorithms were devised for the comparison of these data from batch to batch. The results of comparing the data base and graphical information were used to identify discrepancies between fermentations and determine cause-effect relationships. The comparative techniques were used to analyse the data from a set of recombinant, protein producing, laboratory scale fermentations and thus enable reasoning about the effects of sterilisation conditions and inoculum concentration on the progress of the fermentation. The results concurred with manual analysis of the data. The computerised tools improved understanding of the process because all available data could be analysed in a thorough and consistent manner. The comparative reasoning tools have the potential to improve the on-line detection and diagnosis of faults in a production process and can provide a link between fermentation and downstream processing data analysis. The comparative reasoning tools require no a priori knowledge of the process and can be applied to any type of data with no dependence on the magnitude of the values. The tools can therefore be used in both research and production environments and on any fermentation process.

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