Bioethanol subproducts as a basis of plant biorefinery

The philosophy of our research is built on the behaviour of non-sugar compounds from biomass during ethanolic fermentation. Saccharomyces cerevisiae, industrially used to bioconvert sugar into ethanol under anaerobic conditions, assimilates some compounds present in the fermentable juice (proteins, amino acids,...). But others compounds are not used by the yeast. They leave in the vinasse after ethanol distillation and are thus concentrated by the process. Our purpose is to discuss the behaviour of betaine, saponins and raffinose in sugar juices (raw juice, thin juice, thick juice) and in vinasse after ethanolic fermentation. An attention will be given to some high added value products (like betaine) and the potentialities to use fermentation as a tool of purification in white chemistry

Survival and preservation after freeze-drying process of thermoresistant acetic acid bacteria isolated from tropical products of Subsaharan Africa

Two thermoresistant acetic acid bacteria (TAAB) were previously isolated and selected for a sustainable development of vinegar fermentation in Subsaharan Africa. Their use as a starter culture in vinegar manufactures in such regions could reduce considerably water cooling expenses. For optimising biomass preservation, the effect of 20% w/w mannitol as cryoprotectant on the cells viability after freeze-drying process and during storage was evaluated. Results showed that freeze-dried cells could be conserved at 4 degrees C for at least 6 months without loss of viability. The main reasons were that cryoprotectant tends to lower the water activity (a(w)) and to maintain a temperature of product weaker than that of the glass transition temperature T-g. Furthermore, the heat resistance of freeze-dried cells during storage was all the more increased that strains were cryoprotected. In addition, intrinsically, an increase of saturated fatty acids with the temperature is the essential modification in the lipidome level of membrane cells when the fermentation occured at a temperature of 30 degrees C. Tolerance to heat during storage was significantly enhanced under such mechanisms. (c) 2006 Elsevier Ltd. All rights reserved

Acetobacter senegalensis sp nov., a thermotolerant acetic acid bacterium isolated in Senegal (sub-Saharan Africa) from mango fruit (Mangifera indica L.)

peer reviewedA thermotolerant acetic acid bacterium, designated strain CWBI-B418(T), isolated in Senegal from mango fruit (Mangifera indica), was characterized in detail by means of genotypic and phenotypic methods. The novel strain was strictly aerobic and exhibited optimal growth on YGM medium at 35 degrees C. Cells were Gram-negative, motile and coccoid. The strain was assigned to the genus Acetobacter on the basis of 16S rRNA gene sequence analysis. DNA-DNA hybridization experiments with its phylogenetically closest relatives showed that strain CWBI-B418(T) represented a novel Acetobactergenospecies. The DNA G +C content of strain CWBI-B418(T) was 56.0 mol%. Phenotypic characteristics enabling the differentiation of strain CWBI-B418(T) from phylogenetically related Acetobacter species were: production of 2-keto-D-gluconic acid from D-glucose, but not 5-keto-D-gluconic acid, production of catalase but not oxidase, growth on yeast extract with 30% D-glucose, growth with ammonium as sole nitrogen source with ethanol as carbon source, utilization of glycerol and ethanol but not maltose or methanol as carbon sources, and growth in the presence of 10% ethanol. Based on the genotypic and phenotypic data presented, strain CWBI-B418(T) clearly represents a novel Acetobacter species, for which the name Acetobacter senegalensis sp. nov. is proposed. The type strain is CWBI-B418(T) (=LMG 23690(T) = DSM 18889(T))

Acetobacter senegalensis isolated from mango fruits : its polyphasic characterization and adaptation to protect against stressors in the industrial production of vinegar : a review

It has been more than a decade since Acetobacter senegalensis was isolated, identified and described as a thermotolerant strain of acetic acid bacteria. It was isolated from mango fruits in Senegal and used for industrial vinegar production in developing countries, mainly in sub-Saharan Africa. The strain was tested during several spirit vinegar fermentation processes at relatively high temperatures in accordance with African acclimation. The upstream fermentation process had significant stress factors, which are highlighted in this review so that the fermentation process can be better controlled. Due to its high industrial potential, this strain was extensively investigated by diverse industrial microbiologists worldwide; they concentrated on its microbiological, physiological and genomic features. A research group based in Belgium proposed an important project for the investigation of the whole-genome sequence of A. senegalensis. It would use a 454-pyrosequencing technique to determine and corroborate features that could give this strain significant diverse bio-industrial applications. For instance, its application in cocoa bean fermentation has made it a more suitable acetic acid bacterium for the making of chocolate than Acetobacter pasteurianus. Therefore, in this paper, we present a review that summarizes the current research on A. senegalensis at its microbial and genomic levels and also its specific bio-industrial applications, which can provide economic opportunities for African agribusiness. This review summarizes the physiological and genomic characteristics of Acetobacter senegalensis, a thermotolerant strain isolated from mango fruits and intended to be used in industrial vinegar fermentation processes. It also explores other bio-industrial applications such as cocoa fermentation. Vinegar fermentation is usually performed with mesophilic strains in temperate regions of the world. Developing countries, such as Senegal, import vinegar or make 'fake' vinegar by diluting acetic acid obtained from petrochemicals. The use of a thermotolerant Acetobacter senegalensis strain as a solid functional starter culture, as well as the design of a new adapted bioreactor, has significantly contributed to food security and the creation of small- to medium-sized enterprises that produce mango vinegar in West Africa

Pearl millet genotype impacts microbial diversity and enzymatic activities in relation to root-adhering soil aggregation

International audienceThe interactions between plant roots and the associated microbiota impact soil aggregation, water retention and plant nutrient availability. Thus, selection of plant genotypes that promote microbial species involved in rootadhering soil aggregation and rhizosheath formation could help improve yield sustainably. Here, we tested pearl millet genotypic variation in both root-adhering soil aggregation, microbiological and biochemical characteristic. Methods: A collection of 181 pearl millet inbred lines was phenotyped for their rhizosheath size, and thirteen contrasting genotypes were selected and grown under field conditions, and their root-adhering soil (RAS) was sampled. Microbial biomass, pH, mineral N content and six enzymatic activities involved in main nutrients cycles were analyzed, and metabarcoding of 16S rDNA and ITS were performed for bacterial and fungal diversity. Results: Enzymatic activities (chitinase, acid phosphomonoesterase, FDA-hydrolysis and β-glucosidase) were higher in RAS of larger rhizosheath lines than that of smaller rhizosheath one. Bacterial β-diversity showed a separation of the most contrasting lines in the principal coordinate analysis performed with the Bray-Curtis distance. Some bacteria from the Gaiellaceae and Sphingomonadaceae families and the Bradyrhizobium genus were associated with the large rhizosheath phenotype. Concerning the fungal community, we noticed a negative correlation between the specific richness and the rhizosheath size and Trichoderma genus was positively associated to the rhizosheath size. Conclusions: This study demonstrates that in pearl millet, rhizosheath size is related to soil nutrient dynamics and microbiota diversity. However, it also shows that other factors shape this trait and their relative importance must be determined