Effects of drought-induced holm oak dieback on BVOCs emissions in a Mediterranean forest.

Climate change is impairing tree physiology and growth, causing an increase in tree dieback in many Mediterranean forests. These desiccation phenomena are leading to changes in land cover and plant community composition. Mediterranean plants are capable to emit large amount of Biogenic Volatile Organic Compounds (BVOCs), whose emission and biosynthesis is strongly affected by environmental conditions. This study evaluates the seasonal changes in understory species composition in two forest stands in Southern Tuscany characterized by different levels of Quercus ilex L. crown defoliation (low and high defoliation, LD and HD) and the relationship with BVOCs emissions over three years. We found significant changes in the understory plant community following Q. ilex crown defoliation and mortality, observing an increment in the number of shrubs both in HD and LD stands. The environmental sampling of BVOCs fully reflected the changes in vegetation cover and composition, with a reduction in the amount of monoterpene emissions due to the increasing rates of defoliation and mortality of Q. ilex trees. Our results suggest that terpene emissions from Mediterranean forests would be modified by an increase of Q. ilex dieback, with important consequences for functioning of this forest ecosystem and its atmospheric chemistry.

Biomass sorghum as a novel substrate in solid-state fermentation for the production of hemicellulases and cellulases by Aspergillus niger and A. fumigatus.

AIMS: We investigated the role of carbon and nitrogen sources in the production of cellulase and hemicellulase by Aspergillus strains. METHODS AND RESULTS: The strains Aspergillus niger SCBM1 and Aspergillus fumigatus SCBM6 were cultivated under solid-state fermentation (SSF), with biomass sorghum (BS) and wheat bran (WB) as lignocellulosic substrates, in different proportions, along with variable nitrogen sources. The best SSF condition for the induction of such enzymes was observed employing A. niger SCBM1 in BS supplemented with peptone; maximum production levels were achieved as follows: 72 h of fermentation for xylanase and exoglucanase (300·07 and 30·64 U g-1 respectively), 120 h for ß-glucosidase and endoglucanase (54·90 and 41·47 U g-1 respectively) and 144 h for ß-xylosidase (64·88 U g-1 ). CONCLUSIONS: This work demonstrated the viability of the use of BS for the production of hemi- and cellulolytic enzymes; the high concentration of celluloses in BS could be associated with the significant production of cellulases, mainly exoglucanase. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study which presents the promising use of biomass sorghum (genetically modified sorghum to increase its biomass content) as an alternative carbon source for the production of enzymes by SSF.

Novel thermoplastic materials based on the outer-shell oxypropylation of corn starch granules.

The study of the plasticization of corn-starch granules through the bulk oxypropylation of their outer shell produced a novel biphasic material consisting of a low glass transition temperature component surrounding the granules' inner core, which could be hot pressed to form films of the granules dispersed into a thermoplastic matrix. The success and extent of these chemical modifications and the properties of the ensuing composites were assessed by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and contact angle measurements. This approach has the additional advantage of being simple and "green".

Lignin from sugar cane bagasse: extraction, fabrication of nanostructured films, and application.

Four lignin samples were extracted from sugar cane bagasse using four different alcohols (methanol, ethanol, n-propanol, and 1-butanol) via the organosolv-CO2 supercritical pulping process. Langmuir films were characterized by surface pressure vs mean molecular area (Pi-A) isotherms to exploit information at the molecular level carrying out stability tests, cycles of compression/expansion (hysteresis), subphase temperature variations, and metallic ions dissolved into the water subphase at different concentrations. Briefly, it was observed that these lignins are relatively stable on the water surface when compared to those obtained via different extraction processes. Besides, the Pi-A isotherms are shifted to smaller molecular areas at higher subphase temperatures and to larger molecular areas when the metallic ions are dissolved into the subphase. The results are related to the formation of stable aggregates (domains) onto the water subphase by these lignins, as shown in the Pi-A isotherms. It was found as well that the most stable lignin monolayer onto the water subphase is that extracted with 1-butanol. Homogeneous Langmuir-Blodgett (LB) films of this lignin could be produced as confirmed by UV-vis absorption spectroscopy and the cumulative transfer parameter. In addition, FTIR analysis showed that this lignin LB film is structured in a way that the phenyl groups are organized preferentially parallel to the substrate surface. Further, these LB films were deposited onto gold interdigitated electrodes and ITO and applied in studies involving the detection of Cd+2 ions in aqueous solutions at low concentration levels through impedance spectroscopy and electrochemical measurements. FTIR spectroscopy was carried out before and after soaking the thin films into Cd+2 aqueous solutions, revealing a possible physical interaction between the lignin phenyl groups and the heavy metal ions. The importance of using nanostructured systems is demonstrated as well by comparing both LB and cast films.

Nanostructured films employed as sensing units in an "electronic tongue" system.

Nanostructured films of lignin (macromolecule extracted from sugar cane bagasse), polypyrrole (conducting polymer) and bis butylimido perylene (organic dye) were used in the detection of trace levels of fluorine (from H2SiF6), chlorine (from NaClO), Pb(+2), Cu(+2), and Cd(+2) in aqueous solutions. Langmuir monolayers on ultrapure water were characterised by surface pressure-mean molecular area (II-A) isotherms. Langmuir-Blodgett (LB) films were transferred onto gold interdigitated electrodes and used as individual sensing units of an electronic tongue system. Impedance spectroscopy measurements were taken with the sensor immersed into aqueous solutions containing the ions described above in different molar concentrations. Fourier transform infrared absorption (FTIR) was employed to identify possible interactions between the LB films and the analytes in solution, and no significant changes could be observed in the FTIR spectra of BuPTCD and Ppy. Therefore, the results for lignin point to an interaction involving the electronic cloud of the phenyl groups with the metallic ions.

Evaluation of glass sampling tubes for industrial breath analysis.

The storage of halogenated hydrocarbons in breath and air samples in glass cylindrical tubes was investigated to determine procedures to achieve a representative breath sampling technique. The loss of solvent vapor concentration over a fixed time period was observed and postulated to result from non-reactive absorption. If considerations are made for adverse sampling conditions of moisture, temperature, and tube surface condition, glass tubes prove to be an acceptable container for breath samples.