Parametric Sensitivity of CSTBRs for Lactobacillus casei: Normalized Sensitivity Analysis

Subhashis Das,Rajnish Kaur Calay,Ranjana Chowdhury

doi:10.3390/chemengineering4020041

Subhashis Das, Rajnish Kaur Calay + Show 1 more

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https://doi.org/10.3390/chemengineering4020041

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Abstract

In this paper, a sensitivity analysis of a continuous stirred tank bioreactor (CSTBR) was conducted to determine a parametrically sensitive regime. The growth of a lactic acid bacterium, namely, Lactobacillus casei, in a pH-controlled CSTBR was considered as a process model. Normalized objective sensitivities of the minimum pH were determined with respect to input parameters. A generalized criterion for sensitivity was defined for determining the parametric range of three input variables, i.e., dilution rate base stream (θ), base concentration (R), and initial pH (pH0) for maintaining optimal pH range in the reactor. The system exhibits sensitive behavior for θ, R, and pH0, from 0.095 to 0.295, 0 to 0.865, and 4.42 to 4.77, respectively. The critical values of θ, R, and pH0 are 0.0195, 0.48, and 4.6, respectively. The mathematical model can also be used to determine a parametrically sensitive regime for other important parameters, namely, temperature, the concentration of metabolites, and other byproducts. The mathematical tool can also be used in bioreactor design and the improvement of control strategies.

Highlights

Continuous stirred tank reactors are the most widely used reactors for continuous and large scale production in many industries due to their high flexibility
This paper presents the behavior of a continuous stirred tank bioreactor (CSTBR) using lactic acid bacteria, namely, L. casei, through parametric sensitivity analysis
The sensitivity analysis was conducted with respect to three dimensionless input variables, dilution rate θ; base concentration, R, and initial pH, pH0

Summary

Introduction

Continuous stirred tank reactors are the most widely used reactors for continuous and large scale production in many industries due to their high flexibility. The reactors used for bioprocesses are termed as continuous stirred type bioreactors (CSTBR). When the output variables of a system change drastically with a small variation of input parameters, the specific range of that input parameter is called parametric sensitivity region of the system. Once a biochemical system undergoes through this parametric sensitivity region, its performance becomes unpredictable because outputs change sharply with a small variation of the input variable. For all chemical and biological processes, there exists a parametric range within which a process becomes unstable and unreliable, where even small variations in parameters abruptly change the performance. It is important to investigate a change in the behavior of a system with respect to any change in parameters Such a study is called parametric sensitivity analysis [1]. In the context of chemical reactors, Bilous and Amundson [2] first introduced this concept of parametric sensitivity and runaway (where the system becomes unstable)

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