I. de Ory

Modelling the kinetics of growth of Acetobacter aceti in discontinuous culture: influence of the temperature of operation

Acetic acid fermentation is the biochemical process by which, under strict conditions of aerobiosis, Acetobacter aceti oxidises the ethanol contained in alcoholic substrates into acetic acid. This paper studies the effect of temperature on the specific growth rate of the microorganisms (μC), in particular, the mathematical modelling of this process, with the aim of developing previous studies of the mathematical relationships between μC of A. aceti and the concentrations of substrate (ethanol), product (acetic acid) and dissolved oxygen. Until now this relationship has not been widely studied, and only a few studies have looked at the influence of temperature on growth kinetics of this bacteria. We have developed an extensive experimental system, to determine precisely the influence of temperature on the maximum specific growth rate.

Valorization of exhausted sugar beet cossettes by successive hydrolysis and two fermentations for the production of bio-products

Exhausted sugar beet cossettes (ESBC) show an enormous potential as a source of sugars for the production of bio-products. Enzyme hydrolysis with the combined effect of mainly cellulases, xylanases and pectinases, turned out to be very efficient, obtaining almost double the concentration of sugars measured with the sole action of Celluclast® and β-glucosidase, and increasing 5 times the hydrolysis rate. As the sole pretreatment, ESBC soaked in the hydrolysis buffer were autoclaved, avoiding the application of severe conventional biomass pretreatments. Moreover, a promising alternative for the complete utilization of glucose, xylose, arabinose, mannose and maltose contained in ESBC is proposed in this paper. It consists of sequential fermentation of sugars released in the hydrolysis step to produce bioethanol and lactic acid as main bio-products. Compared to separate fermentations, with this strategy glucose and hemicellulose derived sugars were completely consumed and the 44% of pectin derived sugars.

Laboratory scale equipment for the determination of kLa in bio-reactors

Abstract The study of the oxygen transfer rate (O.T.R) in reactors designed for cell cultivation and enzyme reaction is a difficult task. In this work a bio-reactor for acetic acid fermentation purposes is studied by using the static gassing out method for KLa evaluation. Results obtained prove that KLa shows linear dependence versus operation temperature.