Michel Fick

Impact of shear stress and impeller design on the production of biogas in anaerobic digesters

Today, intensification of anaerobic digestion is still a scientific and technical challenge. The present study proposed combined experimental and computational fluid dynamics simulations to characterize the impact of shear stress and impeller design on the biogas production after sequential additions of substrate. Liquid phase (cattle manure digestate) rheological law was experimentally determined and input in numerical simulations. The results showed that the original use of a double helical ribbon in digester allowed a significantly faster dispersion of fresh substrate than the use of a classical Rushton turbine, leading to a 50% higher methane production rate. However, with both impellers, too high agitation rates entailed a clear slow-down of production rate and a decrease in CH4 content. To avoid this loss of productivity, it was shown that the maximal value of shear stress, determined by numerical simulations, was a consistent parameter to set the upper agitation conditions in digesters.

On-line estimation of lactic acid concentration by conductivity measurement in fermentation broth

On-line estimation of lactic acid concentration in fermentation broth is very feasible with conductivity probe directly in fermenter. This paper shows that lactic acid is the most influent parameter of medium on the conductivity measurements. The precision and longevity of conductivity probe are excellent in normal conditions of lactic acid production by fermentation process.

The deflocculating effect of chloride salts (ions) on Clostridium acetobutylicum grown in continuous cultures

SummaryThe stability of continuous fermentations of Clostridium acetobutylicum can be limited by cell flocculation under conditions of high solvent production. The addition of chloride salts to a synthetic medium prevents the flocculation of the bacteria, and thus results in stable continuous cultures.

Analytical method optimization for protein determination by fast high-performance liquid chromatography

Abstract A method based on fast HPLC allowing the rapid and efficient determination of proteins in mammalian cell cultures is proposed, involving the use of two chromatographic modes, RP-HPLC and high-performance liquid affinity chromatography. These two sequential chromatographic analyses separate the proteins most often used as supplements in serum-free media such as bovine serum albumin, insulin and transferrin, and also monoclonal antibodies secreted by hybridoma in cultures. Rapidity, reliability and flexibility are the main characteristics of the method. The monitoring of proteins in the course of a discontinuous hybridoma culture is presented.

Monitoring of proteins in hybridoma cultures by HPLC

Rapid, accurate and flexible analysis of protein concentrations, and notably IgG concentrations, in crude hybridoma culture media is essential to provide production optimization. An analytical method using two chromatographic columns has been optimized in order to monitor proteins in the course of several cultures and, consequently, to establish the evolution of their concentrations with rapidity and reliability.

Changes inClostridium acetobutylicum during acetone-butanol fermentation detected by measurement of electrophoretic mobility

Changes inClostridium acetobutylicum during acetone-butanol fermentation have been detected by measurement of electrophoretic mobility using a laser doppler particle electrophoresis instrument. These results are shown to correspond to the two stages of the fermentation and to agree with other observations of flocculation and changes in morphology of the microorganisms.