No abstract

In the context of increasing volatility of oil prices, replacement of petroleum based plastics by bioplastics is a topic of increasing interest. Poly(hydroxyalkanoate)s (PHAs) are among the most promising families in this field. Controlling composition of the polymer on the monomeric level remains a pivotal issue. This control is even more difficult to achieve when the polymer is not synthesized by chemists, but produced by nature, in this case, bacteria. In this study mechanism and role of two 3-hydroxyvalerate (3-HV) inducing substrates on the production of PHBV with high, 80%, 3-HV content were evaluated. It was found that levulinic acid contributes to biomass and bio-polymer content enhancement, whereas sodium propionate mainly contributes to 3-HV enhancement. Optimized proportions of feeding substrates at 1 g/L and 2.5 g/L, respectively for levulinic acid and sodium propionate allowed a 100% productivity enhancement, at 3.9 mg/L/hour, for the production of PHBV with 80% 3-HV.

BACKGROUND: Polyhydroxyalkanoates (PHA) are very interesting biopolymers, their most promising applications lie in biomedical science. The wettability of the surface of PHA increases their biocompatibility properties, making them suitable for such applications. RESULTS: The treatment of the surface of poly (3-hydroxybutyrate) (PHB) and poly (3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV) films with the cutinase TfCut2 from Thermobifida fusca KW3 resulted in decrease of the water contact angle of PHB films from 90 ∘ to 36 ∘ and PHBV films from 93-98 ∘ to 50-60 ∘ with 3-hydroxyvalerate content ranging from 6 to 9 mol%, respectively. CONCLUSION: A linear dependence up to 9 mol% was found between the 3-hydroxyvalerate content of the PHBV and the resulting water contact angle decrease, caused by partial hydrolysis of the surface of the films by the cutinase. PHBV films with a 3-hydroxyvalerate content of 6 mol% showed the highest gain in surface hydophilicity following treatment with the enzyme. Preparation of PHA filmsThe films were prepared by a solvent casting technique. A solution of 10 g L −1 of PHA in chloroform was prepared and filtered to remove insoluble parts. 30 g of the solution were poured into Figure 2. SEM of PHB films. (A) untreated; (B), (C) treated with TfCut2 cutinase for 2 h; (D) treated with TfCut2 cutinase for 24 h.

Plant protection is mainly based on the application of synthetic pesticides to limit yield losses resulting from diseases. However, the use of more eco-friendly strategies for sustainable plant protection has become a necessity that could contribute to controlling pathogens through a direct antimicrobial effect and/or an induction of plant resistance. Three different families of natural or bioinspired compounds originated from bacterial or fungal strains have been evaluated to protect wheat against powdery mildew, caused by the biotrophic Blumeria graminis f.sp. tritici (Bgt). Thus, three bio-inspired mono-rhamnolipids (smRLs), three cyclic lipopeptides (CLPs, mycosubtilin (M), fengycin (F), surfactin (S)) applied individually and in mixtures (M + F and M + F + S), as well as a chitosan oligosaccharide (COS) BioA187 were tested against Bgt, in planta and in vitro. Only the three smRLs (Rh-Eth-C12, Rh-Est-C12 and Rh-Succ-C12), the two CLP mixtures and the BioA187 led to a partial protection of wheat against Bgt. The higher inhibitor effects on the germination of Bgt spores in vitro were observed from smRLs Rh-Eth-C12 and Rh-Succ-C12, mycosubtilin and the two CLP mixtures. Taking together, these results revealed that such molecules could constitute promising tools for a more eco-friendly agriculture.

Chitosan is a natural polysaccharide which has been authorized for oenological practices for the treatment of musts and wines. This authorization is limited to chitosan of fungal origin while that of crustacean origin is prohibited. To guarantee its origin, a method based on the measurement of the stable isotope ratios (SIR) of carbon δ13C, nitrogen δ15N, oxygen δ18O and hydrogen δ2H of chitosan has been recently proposed without indicating the threshold authenticity limits of these parameters which, for the first time, were estimated in this paper. In addition, on part of the samples analysed through SIR, Fourier transform infrared spectrometry (FTIR) and thermogravimetric analysis (TGA) were performed as simple and rapid discrimination methods due to limited technological resources. Samples having δ13C values above −14.2‰ and below −125.1‰ can be considered as authentic fungal chitosan without needing to analyse other parameters. If the δ13C value falls between −25.1‰ and −24.9‰, it is necessary to proceed further with the evaluation of the parameter δ15N, which must be above +2.7‰. Samples having δ18O values lower than +25.3‰ can be considered as authentic fungal chitosan. The combination of maximum degradation temperatures (obtained using TGA) and peak areas of Amide I and NH2/Amide II (obtained using FTIR) also allows the discrimination between the two origins of the polysaccharide. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) based on TGA, FTIR and SIR data successfully distributed the tested samples into informative clusters. Therefore, we present the technologies described as part of a robust analytical strategy for the correct identification of chitosan samples from crustaceans or fungi.