Using sliding mode observers to estimate concentration from measured vitamin B concentration.

A simple model for the B-riboswitch regulatory network in is first described and the same analysis is applied when changing the strain to . Model validation is undertaken by linking the dynamics of the riboswitch model to bacterial growth and comparing the results obtained with in vivo experimental measurements. Measurements of bacterial growth are relatively straightforward to obtain experimentally, but experimental measurements relating to the operation of the riboswitch are more difficult. Using the validated model, sliding mode observer design methods are used to estimate given measurements of the concentration of vitamin B. The sliding mode approach is selected because of its inherent robustness properties as well as for the ease of implementation. Validation of the estimates of produced by the observer is undertaken by comparing the and vitamin B concentrations estimated from the observer with green fluorescent protein production and the concentration of vitamin B obtained experimentally. These experimental results also provide further validation of the underpinning mathematical model. The results establish that using a sliding mode observer as a soft sensor is a useful approach to explore the operation of a vitamin B riboswitch given measurements of the concentration of vitamin B.