Kalle Salonen

On-line biomass measurements in bioreactor cultivations: comparison study of two on-line probes.

Two on-line probes for biomass measurement in bioreactor cultivations were evaluated. One probe is based on near infrared (NIR) light absorption and the other on dielectric spectroscopy. The probes were used to monitor biomass production in cultivations of several different microorganisms. Differences in NIR probe response compared to off-line measurement methods revealed that the most significant factor affecting the response was cell shape. The NIR light absorption method is more developed and reliable for on-line in situ biomass estimation than dielectric spectroscopy. The NIR light absorption method is, however, of no significant use, when the cultivation medium is not clear, and especially in processes using adsorbents or solid matrix for the microorganism to grow on. The possibilities offered by dielectric spectroscopy are impressive, but the on-line probe technology needs to be improved.

Developing a multipoint titration method with a variable dose implementation for anaerobic digestion monitoring

Determination of metabolites from an anaerobic digester with an acid base titration is considered as superior method for many reasons. This paper describes a practical at line compatible multipoint titration method. The titration procedure was improved by speed and data quality. A simple and novel control algorithm for estimating a variable titrant dose was derived for this purpose. This non-linear PI-controller like algorithm does not require any preliminary information from sample. Performance of this controller is superior compared to traditional linear PI-controllers. In addition, simplification for presenting polyprotic acids as a sum of multiple monoprotic acids is introduced along with a mathematical error examination. A method for inclusion of the ionic strength effect with stepwise iteration is shown. The titration model is presented with matrix notations enabling simple computation of all concentration estimates. All methods and algorithms are illustrated in the experimental part. A linear correlation better than 0.999 was obtained for both acetate and phosphate used as model compounds with slopes of 0.98 and 1.00 and average standard deviations of 0.6% and 0.8%, respectively. Furthermore, insensitivity of the presented method for overlapping buffer capacity curves was shown.

BIOREACTOR MEASUREMENT AND SIMULATION ENVIRONMENT

Abstract The aim of the work was to generate a flexible measurement, control and simulation environment for laboratory and pilot scale experiments. Various measurement devices were connected and synchronized to an integrated system with many bioreactors. Integrated devices were for example biomass monitoring, mass spectrometer and glucose control. Microcontroller-based interface modules and device drivers capable of transferring data to Multi Fermentor Control System (MFCS) via software interface were developed for each integrated device. A simple network TCP/IP interface enabled to distribute measurement devices in the laboratory intranet. The final result was an enhanced and flexible bioreactor data acquisition system.