Analysis of some functional properties of acetic acid bacteria involved in Ivorian cocoa fermentation

Objective: To investigate some functional properties of acetic acid bacteria (AAB), involved in Côte d’Ivoire cocoa fermentation.Methods and results: Six day heap fermentation on banana leaves was conducted at farm level and AAB growth was monitored during this process at 24 h interval by numeration on plate agar. Functional properties such as acid production, thermotolerance, resistance to alcoholic stress carbon metabolism and over oxidation of acetic acid were conducted on either plate agar or liquid medium. During fermentation, AAB reached maximum load at 72 h, corresponding to a high temperature 44 °C of fermenting mass and a pH round 4.45. All the 86 strains isolated proved to be thermotolerant with ability to grow up to 45 °C and 63 % of them showed particularly high tolerance to alcohol up to 15 %. The temperature between 30 and 40 °C and alcohol at high concentration (15 %) did not notably affect acid production. However, beyond 40 °C, the acidification ability of the most acidifying strains was strongly affected. A high proportion of strains 80 %, were able to further oxidize acetic acid into water and carbon dioxide and subsequently belong to Acetobacter genus. The strains displayed a poor carbon metabolism profile with the capacity to utilize only glucose as carbon source.Conclusion and application of findings: This study shows that Ivoirian AAB fermenting mass possesses some technological traits potentially useful for their utilization as valuable starters in cocoa fermentation.Key words: Acetic acid bacteria, alcohol-tolerance, cacao, fermentation, thermotolerance

Low-Income Countries and an SDR-based International Monetary System

The global financial crisis, the weakening role of the dollar and the increasing international importance of China are calling for a reform of the international monetary system in the direction of greater multilateralism. To this end, we advance a proposal based on a greater role of the Special Drawing Rights (SDRs) and focus on the potential benefits that these could bring to Low-Income Countries (LICs). SDRs would be created exogenously - with a disproportionate allocation to LICs -, but also endogenously, through a substitution account and an overdraft facility. Finally, the paper discusses the superiority of this proposal in the context of the current foreign assistance framework

Temperature- and pH-Sensitive Nanohydrogels of Poly(N-Isopropylacrylamide) for Food Packaging Applications: Modelling the Swelling-Collapse Behaviour

Temperature-sensitive poly(N-isopropylacrylamide) (PNIPA) nanohydrogels were synthesized by nanoemulsion polymerization in water-in-oil systems. Several cross-linking degrees and the incorporation of acrylic acid as comonomer at different concentrations were tested to produce nanohydrogels with a wide range of properties. The physicochemical properties of PNIPA nanohydrogels, and their relationship with the swelling-collapse behaviour, were studied to evaluate the suitability of PNIPA nanoparticles as smart delivery systems (for active packaging). The swelling-collapse transition was analyzed by the change in the optical properties of PNIPA nanohydrogels using ultraviolet-visible spectroscopy. The thermodynamic parameters associated with the nanohydrogels collapse were calculated using a mathematical approach based on the van't Hoff analysis, assuming a two-state equilibrium (swollen to collapsed). A mathematical model is proposed to predict both the thermally induced collapse, and the collapse induced by the simultaneous action of two factors (temperature and pH, or temperature and organic solvent concentration). Finally, van't Hoff analysis was compared with differential scanning calorimetry. The results obtained allow us to solve the problem of determining the molecular weight of the structural repeating unit in cross-linked NIPA polymers, which, as we show, can be estimated from the ratio of the molar heat capacity (obtained from the van't Hoff analysis) to the specific heat capacity (obtained from calorimetric measurements)