Software sensor design considering oscillating conditions as present in industrial scale fed-batch cultivations

• Published in: Biotechnology and bioengineering 2013-07, Vol.110 (7), p.1945-1955
• Main Authors: Lyubenova, V., Junne, S., Ignatova, M., Neubauer, P.
• Format: Article
• Language: English
• Subjects: Bacillus subtilis; Bacillus subtilis - growth & development; Bacillus subtilis - metabolism; Bacteria; Bioreactors - microbiology; Biotechnology - methods; Computer Simulation; Culture Media - chemistry; Glucose; Glucose - metabolism; industrial scale fed-batch processes; inhomogeneities; Kinetics; scale down reactor; Simulators; Software; software sensor design; tuning procedure
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.24870

Investigations of inhomogeneous dynamics in industrial‐scale bioreactors can be realized in laboratory simulators. Such studies will be improved by on line observation of the growth of microorganisms and their product synthesis at oscillating substrate availability which represents the conditions in industrial‐scale fed‐batch cultivations. A method for the kinetic monitoring of such processes, supported by on line measurements accessible in industrial practice, is proposed. It consists of a software sensor (SS) system composed of a cascade structure. Process kinetics are simulated in models with a structure including time‐varying yield coefficients. SSs for measured variable kinetics have classical structures. The SS design of unmeasured variables is realized after a linear transformation using a logarithmic function. For these software sensors, a tuning procedure is proposed, at which an arbitrary choice of one tuning parameter value that guarantees stability of the monitoring system allows the calculation of the optimal values of six parameters. The effectiveness of the proposed monitoring approach is demonstrated with experimental data from a glucose‐limited fed‐batch process of Bacillus subtilis in a laboratory two‐compartment scale down reactor which tries to mimic the conditions present in industrial scale nutrient‐limited fed‐batch cultivations. Biotechnol. Bioeng. 2013; 110: 1945–1955. © 2013 Wiley Periodicals, Inc. A method is described for monitoring of industrial‐scale fed‐batch processes with a step‐wise software sensor approach composed of a cascade structure. Process kinetics are simulated considering time‐varying yield coefficients. The software sensor design is realized after a linear transformation using a logarithmic function. The effectiveness of the proposed monitoring approach is demonstrated with experimental data of biomass, oxygen consumption and the respiratory quotient of Bacillus subtilis fed‐batch cultivations in a two‐compartment scale‐down reactor.