Evaluation of a set of E. coli reporter strains as physiological tracer for estimating bioreactor hydrodynamic efficiency

in Process Biochemistry (2010), 45(11), 1769-1778

A set of different green fluorescent protein (GFP) Escherichia coli reporter strains have been evaluated in mini- and stirred bioreactors operating in fed-batch mode with different degrees of ... [more ▼]

A set of different green fluorescent protein (GFP) Escherichia coli reporter strains have been evaluated in mini- and stirred bioreactors operating in fed-batch mode with different degrees of perturbations in order to estimate their potential use as process-related stress biosensor. The mini-bioreactor platform comprises a set of parallel shake flasks operating in fed-batch mode. The advantage of this system is its high experimental throughput for the evaluation of the GFP synthesis capacity of our reporter strains. In the case of classical shake flask system, no significant evolution of GFP synthesis have been observed, considering the reduced microbial growth period allowed by the system, whereas in the case of fed-batch operated mini-bioreactors, evolution of GFP synthesis, as well as GFP distribution among the microbial population, has been observed for three preselected strains (prpoS, puspA and posmC::gfp). More interestingly, a binary mode of expression has been observed in the case of the cultures carried out with the reporter strains for which GFP synthesis is under the control of the rpoS promoter which is induced under carbon limitation conditions. However, the generation of controlled glucose perturbations is relatively limited in this system and, in a second step fully automated bioreactor with a sclae-down strategy has been used to correlate the response of a prpoS::gfp strains with extracellular glucose perturbations. In the case of the culture performed in perturbed bioreactor (glucose intermittent feeding or glucose addition at the level of the recycle loop of a two-compartment scale-down bioreactor), the slowdown of the GFP synthesis resulting in the observation of a binary repartition of GFP content among the microbial population, has been observed. This observation led to the conclusion that the prpoS::gfp can be used as a biosensor for the validation of a fed-batch profile in industrial-scale bioreactors. [less ▲]

Beneficial effects of Bacillus subtilis on field-grown tomato in Burundi : reduction of local Fusarium disease and growth promotion.

in African Journal of Microbiology Research [=AJMR] (2010), 4

Development of a biotransformation process of hydroperoxides into green leaf volatiles using sugar beet leaves

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010)

Natural green leaf volatiles (GLVs) are commonly sole AS aldehydic and alcoholic flavors; their synthesis is a great challenge for industry. Especially, the bioconversion step of fatty acid hydroperoxides ... [more ▼]

Natural green leaf volatiles (GLVs) are commonly sole AS aldehydic and alcoholic flavors; their synthesis is a great challenge for industry. Especially, the bioconversion step of fatty acid hydroperoxides into aldehydes by the hydroperoxide lyase (HL). This widely studied enzyme is present in cell membranes of green organs from superior plants. Extracted from its natural condition, HL is subject to a suicidal behavior, being irreversibly inhibited by its own substrate. Furthermore, GLVs produced are highly volatile and quickly degraded by other plant enzymes. Thence, high GLVs levels in industrial production are very difficult to obtain, but several biotechnological tools could be developed to enhance this natural synthesis level more than hundred times. This paper will describe a new method for GLVs production in bioreactor using sugar beet leaves as source of HL. One step reaction, including hydroperoxide metabolisation and GLVs extraction, is performed during a short time process. Downstream processing to dispose of natural and pure GLVs molecule will also be discussed. [less ▲]

Differential roles of lipopeptides(LPs) in plant host defenses and pathogen suppression.

Conference (2010)

Development of a biotransformation process of hydroperoxydes into green leaf volatiles using sugar beet leaves.

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14 (S2)

Production d’arômes de type lactone par des levures.

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14(4), 681-691

Etude comparative des composés phénoliques, du pouvoir antioxydant de différentes variétés de sorgho sénégalais et des enzymes amylolytiques de leur malt

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14(1), 131-139

The study involved seven cultivars of white sorghum selected to ISRA Bambey and consumed in many regions of Senegal. Several characters and biochemical compounds of the grains (presence of pigmented testa ... [more ▼]

The study involved seven cultivars of white sorghum selected to ISRA Bambey and consumed in many regions of Senegal. Several characters and biochemical compounds of the grains (presence of pigmented testa, total phenols, condensed tannins and antioxidant activity) were determined in all cultivars. A three days malting was also carried out and amylolytic enzymes such as α-amylase, β-amylase and limit-dextrinase which are essential for a malt of good quality were proportioned. These enzymes are measured specifically with kits of Megazyme: Amylazyme (α-amylase), Betamyl (β-amylase) and Limit-Dextrizyme (limit-dextrinase). Two cultivars, CE 180-33 and CE 145-66 proved to be tannin sorghums, have the highest levels in total phenols and the most important antioxidant activities (ABTS and DPPH). The results of enzymatic analysis and the index of Kolbach indicated the F-2-20 like cultivar presenting the best potentialities for malt production [less ▲]

Combined use of bacteriocin-producing strains to control Listeria monocytogenes regrowth in raw pork meat.

in International Journal of Food Science & Technology (2010), 45

From cells to model membranes: study of the mechanism of action of surfactin, a bacterial elicitor of defence mechanism in plants

Poster (2010)

The use of Macronet resins to recover decalactone produced by Rhodotorula aurantiaca from the culture broth

in Journal of Industrial Microbiology & Biotechnology (2010), 37(2), 167-172

During the biotransformation of castor oil into -decalactone, R. aurantiaca produced both the lactone form and its precursor (4-hydroxydecanoic acid). After six days of culture, a maximum yield of ... [more ▼]

During the biotransformation of castor oil into -decalactone, R. aurantiaca produced both the lactone form and its precursor (4-hydroxydecanoic acid). After six days of culture, a maximum yield of -decalactone of 6.5 g/l was obtained. The parameters of -decalactone adsorption on three Macronet resins (MN-202, MN-102 and MN-100) were investigated in water. Adsorption isotherms of -decalactone for the three Macronet resins were linear. The trapping of -decalactone produced by R. aurantiaca on these resins was then carried out. -Decalactone was eVectively retained by all the studied Macronet resins. The resin MN-202 trapped -decalactone more eYciently than MN-102 and MN-100. The percentages of -decalactone adsorbed on the resins MN-202, MN-102 and MN-100 were, respectively, 85, 75 and 81%, whereas around 70% of the adsorbed -decalactone was then desorbed. We propose an industrial process that uses Macronet resins to extract -decalactone from culture broth of R. aurantiaca. [less ▲]