Publications by Sergio Valentinotti

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Optimal control of fed-batch fermenters S. Valentinotti† C. Cannizzaro‡ M.Rhiel‡ U. Holmberg† U. von Stockar‡ D. Bonvin† †Institut d’Automatique, EPFL, 1015 Lausanne, Switzerland ‡Institut de Genie Chimique, EPFL, 1015 Lausanne, Switzerland Fermentors are often run in a fed-batch manner to avoid the formation of overﬂow metabolites. At a high growth rate, the most eﬃcient metabolic pathway(s) of certain microorganisms become saturated resulting in overﬂow metabolite production. These byproducts are undesira

Comprehensive in-situ bioreactor monitoring and control based on a midinfrared spectroscopic sensor system M. Rhiel1, C. Cannizzaro1, S. Valentinotti2, I. Marison1, U. von Stockar1 1 Institute of Chemical Engineering, 2Institute of Automatic Control Swiss Federal Institute of Technology (EPFL), CH- 1015 Lausanne, Switzerland Abstract A mid-infrared spectroscopic sensor system consisting of a spectrometer, a single attenuated total reflectance (ATR) probe immersed in the bioreactor, and a software package fo

A review, with refs. This contribution analyzes the position of biochem. engineering in general and bioprocess engineering particularly in the force fields between fundamental science and applications, and between academia and industry. By using culture technol. as an example, it can be shown that bioprocess engineering has moved slowly but steadily from an empirical art concerned with mainly know-how to a science elucidating the know-why of culture behavior. Highly powerful monitoring tools enable biochem.

Bacterial exopolysaccharides (EPS) have unique rheol. properties due to their high purity and regular structure. Thus, the food industry frequently uses EPS as thickening, gelling or stabilizing agents. The strain Gluconacetobacter xylinus I 2281 is capable of producing with a very high yield a new sol. EPS named gluconacetan, which is composed of rhamnose, glucose, mannose and glucuronic acid. Growth of these bacteria presents many features that represent a real challenge for both monitoring and control. H

Accurate online monitoring of biomass is an enduring problem. Of the various methods available, one of the more satisfactory is with dielec. spectroscopy (often referred to as capacitance monitoring). However, as this technique measures total -biovolume', large changes in cellular morphol. or population distribution will alter the calibration with respect to cell wt. or no. In an attempt to minimize this problem, the full dielec. spectrum was scanned every 10-20 min, and then multivariate techniques were us

A partial least-squares calibration model, relating mid-IR spectral features with fructose, ethanol, acetate, gluconacetan, phosphate and ammonium concns. has been designed to monitor and control cultivations of Gluconacetobacter xylinus and prodn. of gluconacetan, a food grade exopolysaccharide (EPS). Only synthetic solns. contg. a mixt. of the major components of culture media have been used to calibrate the spectrometer. A factorial design has been applied to det. the compn. and concn. in the calibration

At high growth rates, the biomass yield of baker's yeast (Saccharomyces cerevisiae) decreases due to the prodn. of ethanol. For this reason, it is std. industrial practice to use a fed-batch process whereby the specific growth rate, m, is fixed at a level below the point of ethanol prodn., i.e., mcrit. Optimally, growth should be maintained at mcrit, but in practice, this is difficult because mcrit is dependent upon strain and culture conditions. In this work, growth was maintained at a point just above mcr

Over the past decade the interest for bioprocess monitoring using non-invasive IR spectroscopic sensors has increased considerably. This is mainly due to their rapid simultaneous multi-analyte detn. ability, in-situ sterilizability, and low need for maintenance during operation. Most of the components in culture media absorb in the MID-IR region. The complex spectra obtained can be deconvoluted using numerical methods such as Partial Least-Squares. In order to do this, a calibration model for each component

In order to reduce the large calibration matrix usually required for calibrating multiwavelength optical sensors, a simple algorithm based on the addn. in process of new stds. is proposed. A small calibration model, based on 14 stds., is periodically updated by spectra collected online during fermn. operation. Concns. related to these spectra are reconciled into best-estd. values, by considering carbon and oxygen balances. Using this method, fructose, acetate, and gluconacetan were monitored during batch fe

A direct adaptive control methodology for the rejection of unmeasured non-vanishing disturbances is proposed. The approach uses the framework of polynomial RST controllers and relies on the internal model principle with additional degrees of freedom provid ...

Spectroscopic monitoring techniques have many advantages for bioprocess monitoring and control, including simultaneous multi-analyte detns., in-situ sterilizability, and low maintenance during operation. This study discusses the combined application of fluorescence, mid-IR, and Raman spectroscopic techniques for a comprehensive monitoring of Phaffia rhodozyma yeast cultures during batch and fed-batch operation for the prodn. of astaxanthin, a carotenoid of industrial importance. Reliability of the different

Sergio Valentinotti

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Optimal Control of Fed-Batch Fermenters

Comprehensive in-situ Bioreactor Monitoring and Control Based on a Mid-Infrared Spectroscopic Sensor System

Know-how and know-why in biochemical engineering

Adaptive control of a G. xylinus fed-batch fermentation using in situ mid-IR spectroscopy

On-line biomass monitoring with scanning dielectric spectroscopy

Monitoring and control of Gluconacetobacter xylinus fed-batch cultures using in situ mid-IR spectroscopy

Control of yeast fed-batch process through regulation of extracellular ethanol concentration

Experimental versus simulated calibration mdels for in situ FTIR monitoring of bioprocesses

Real-time update of calibration model for better monitoring of batch processes using spectroscopy

Asymptotic Rejection of Nonvanishing Disturbances Despite Plant-Model Mismatch

Bioprocess monitoring and control using the combination of fluorescence, mid-IR, and Raman spectroscopy

Modeling for Control of Fed-Batch Fermenters

Adaptive rejection of unstable disturbances : application to a fed-batch fermentation process

An Optimal Operating Strategy for Fed-Batch Fermentations by Feeding the Overflow Metabolite

An Identification-for-control Procedure with Robust Performance

In-situ Monitoring and Control of Yeast Fermentations with MID-infrared Spectroscopy

Optimal Operation of Fed-Batch Fermentations via Adaptive Control of Overflow Metabolite

Fed-Batch Control of S. Cerevisiae and E. Coli at Critical Point Using Mid-FTIR Spectroscopy

In-Situ Bioreactor Monitoring and Control Based on Mid-Infrared Spectroscopic Measurements