Isabelle Chevalot

Interactions between two carnobacteriocins Cbn BM1 and Cbn B2 from Carnobacterium maltaromaticum CP5 on target bacteria and Caco-2 cells.

Two purified class IIa carnobacteriocins Cbn BM1 and Cbn B2, from Carnobacterium maltaromaticum CP5, were evaluated for antimicrobial activity against pathogenic, spoilage and lactic acid bacteria. Then, the presence of a synergistic mode of action of these two carnobacteriocins on Listeria sp., Enterococcus sp. and Carnobacterium sp. was investigated. A synergistic mode of action between Cbn BM1 and Cbn B2 on sensitive target bacteria was demonstrated using the FIC index method. Combinations of carnobacteriocins enhanced their antibacterial activities and MICs were significantly reduced, between 2- and 15-fold, by the addition of the second bacteriocin. To improve the safety of the bacteriocins as biopreservative agents, the cytotoxicity of the combination of theses two bacteriocins was determined on Caco-2 cell line. However, these two peptides used alone or in combination, at concentration 100-fold higher than those required for antimicrobial activity, were not cytotoxic. This suggests that the two carnobacteriocins produced by C. maltaromaticum CP5 could be potential natural agents for food preservation.

Characterization of chromatographic yeast extract fractions promoting CHO cell growth.

BackgroundMany studies underline the great benefits of yeastextracts (YE), used as supplements in animal free cul-ture media, on cell growth and recombinant proteinproduction [1,2]. Nevertheless, their unknown composi-tion and batch-to-batch variability of commercial YEremain constraints for industrial processes [3,4]. Conse-quently, the identification of bioactive YE molecules ischallenging for process reliability. The main strategy torespond upon this problem is to fractionate the extractand then to characterize the fractions. So far, severalfractionation processes such as ultrafiltration [5], gel fil-tration chromatography [6] or alcoholic precipitation [7]have been investigated. These studies suggested that theactive components were mainly small molecules (< 1000Da). But, the other physico-chemical properties of YEcomponents have been poorly studied until now. Inregards of this statement, it is proposed to get betterknowledge of the YE molecules leading to an improve-ment of CHO cell growth, by implementing variouschromatographic fractionation processes.Material and methodsCHO-AMW cell line producing anti-human RhD-IgG1was provided by Dr. F. Wurm. Cell growth assays wereperformed in 96-well plates with 200μLofworkingvolume inside an incubator at 37 °C and 5 % CO

Study of expansion of porcine bone marrow mesenchymal stem cells on microcarriers using various operating conditions

Background Bone marrow mesenchymal stem cells (BM-MSCs) represent promising source for tissue engineering and cell therapy, due to their multipotency, immunoregulation and self-renewal properties [1,2]. The expansion phase of these cells prior to differentiation and/or injection to the patient remains a critical step. BM-MSCs are classically expanded in small scale culture systems, with low control of culture conditions. However, tissue engineering and cell therapy require very large quantities of cells that cannot be easily achieved using processes in static flasks [3]. Microcarriers, classically used for industrial large scale culture of continuous cell lines, could be advantageously applied to stem cells expansion such as BM-MSCs [4-6]. Our objective was to study the influence of some operating parameters (agitation rate, microcarrier feed) on expansion and organization (adhesion, aggregation) of porcine BM-MSCs cultivated on collagen-free microcarriers, in order to improve cell expansion while maintaining their multipotency.