The use of electric fields for edible coatings and films development and production: A review

Edible films and coatings can provide additional protection for food, while being a fully biodegradable, environmentally friendly packaging system. A diversity of raw materials used to produce edible coatings and films are extracted from marine and agricultural sources, including animals and plants. Electric fields processing holds advantage in producing safe, wholesome and nutritious food. Recently, the presence of a moderate electric field during the preparation of edible coatings and films was shown to influence their main properties, demonstrating its usefulness to tailor edible films and coatings for specific applications. This manuscript reviews the main aspects of the use of electric fields in the production of edible films and coatings, including the effect in their transport and mechanical properties, solubility and microstructure.Fundação para a Ciência e a Tecnologia (FCT), Portugal.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brasil

An Integrated Biorefinery Concept for Conversion of Sugar Beet Pulp into Value-added Chemicals and Pharmaceutical Intermediates

Over 8 million tonnes of sugar beet are grown annually in the UK. Sugar beet pulp (SBP) is the main by-product of sugar beet processing which is currently dried and sold as a low value animal feed. SBP is a rich source of carbohydrates, mainly in the form of cellulose and pectin, including D-glucose (Glu), L-arabinose (Ara) and D-galacturonic acid (GalAc). This work describes the technical feasibility of an integrated biorefinery concept for fractionation of SBP and conversion of these monosaccharides into value-added products. SBP fractionation is initially carried out by steam explosion under mild conditions to yield soluble pectin and insoluble cellulose fractions. The cellulose is readily hydrolysed by cellulases to release Glu that can then be fermented by a commercial Yeast strain to produce bioethanol with a high yield. The pectin fraction can be either fully hydrolysed, using physico-chemical methods, or selectively hydrolysed, using cloned arabinases and galacturonases, to yield Ara-rich and GalAc-rich streams. These monomers can be separated using either Centrifugal Partition Chromatography (CPC) or ultrafiltration into streams suitable for subsequent enzymatic upgrading. Building on our previous experience with transketolase (TK) and transaminase (TAm) enzymes, the conversion of Ara and GalAc into higher value products was explored. In particular the conversion of Ara into L-gluco-heptulose (GluHep), that has potential therapeutic applications in hypoglycaemia and cancer, using a mutant TK is described. Preliminary studies with TAm also suggest GluHep can be selectively aminated to the corresponding chiral aminopolyol. Current work is addressing upgrading of the remaining SBP monomer, GalAc, and modelling of the biorefinery concept to enable economic and Life Cycle Analysis (LCA)

[Comparative study of plasmid resistance to mercury of 2 bacterial strains of animal origin]

International audienceBacterial resistance to mercury has been studied in two different strains from animal origin, Salmonella typhimurium 9205 and Escherichia coli 467. These two strains are resistant to mercuric chloride but sensitive to phenylmercury, and thus belong to the group of bacteria that possess a "narrow" spectrum resistance. The presence of plasmids within the cells has been demonstrated through conjugation experiments and direct detection of extrachromosomal DNA in transconjugants. These plasmids, termed p9205-1 and p467-30, differ from each other by both their size (100 and 50 Kbp, respectively) and structure, as shown by the restriction patterns arising from digestion by nucleases BamHI, HindIII, PstI and EcoRI. Each plasmid has been treated with enzyme SalI to yield DNA fragments that have been cloned into pBR322. Two recombinant plasmids, p9205-1/Sal and p467-30/Sal, have thus been constructed, each of them harboring a 2 Kbp fragment that appears to contain the merA gene coding for mercuric reductase. From the analysis of the restriction maps of these recombinant plasmids as well as the functional behaviour of the bacteria that they are able to transform, it can be concluded that they are identical.Bacterial resistance to mercury has been studied in two different strains from animal origin, Salmonella typhimurium 9205 and Escherichia coli 467. These two strains are resistant to mercuric chloride but sensitive to phenylmercury, and thus belong to the group of bacteria that possess a "narrow" spectrum resistance. The presence of plasmids within the cells has been demonstrated through conjugation experiments and direct detection of extrachromosomal DNA in transconjugants. These plasmids, termed p9205-1 and p467-30, differ from each other by both their size (100 and 50 Kbp, respectively) and structure, as shown by the restriction patterns arising from digestion by nucleases BamHI, HindIII, PstI and EcoRI. Each plasmid has been treated with enzyme SalI to yield DNA fragments that have been cloned into pBR322. Two recombinant plasmids, p9205-1/Sal and p467-30/Sal, have thus been constructed, each of them harboring a 2 Kbp fragment that appears to contain the merA gene coding for mercuric reductase. From the analysis of the restriction maps of these recombinant plasmids as well as the functional behaviour of the bacteria that they are able to transform, it can be concluded that they are identical

Conduction Mechanisms in Hydrogenated Nanocrystalline Silicon

Hydrogenated nanocrystalline silicon (nc-Si:H) is an attractive material for photovoltaic applications, nevertheless some of its physical properties have been investigated only in recent times. In particular, the investigation of the transport mechanisms has up to now led to controversial results. This is mainly due to the complexity of nc-Si:H, as several phases and many defects and impurities coexist. The doping process further increases the complexity of the system as dopant atoms can segregate at nanocrystals (ncs) or at the boundaries between different phases. An extended study of the conduction mechanisms at microscopic level of nc-Si:H thin films is here reported. The films have been deposited by Low Energy Plasma Enhanced Chemical Vapor Deposition, at deposition temperatures from 200 to 400\ub0C and SiH4 dilution ratios from 1% to 50%, which resulted in crystal fractions ranging from 25 to 75%. p-type and n-type doped layers were obtained by using B2H6 and PH3 gases, respectively. Sub-micron resolution current maps have been obtained by conductive atomic force microscopy. In the undoped samples all the maps presented a clear evidence of enhanced conduction in the ncs, while the disordered tissue surrounding them was mostly non-conductive. The conduction, furthermore, occurs mainly at the ncs independently of the crystalline fraction of the films. Doped films show a quite different behavior: nanocrystals are still more conductive than the surrounding tissue, but their localization in the map is different from that of intrinsic films. These results have been compared with macroscopic conductivity measurements. A unified model to interpret both microscopic and macroscopic results is advanced

Particle transport induced by internal wave beam streaming in lateral boundary layers

Quantifying the physical mechanisms responsible for the transport of sediments, nutrients and pollutants in the abyssal sea is a long-standing problem, with internal waves regularly invoked as the relevant mechanism for particle advection near the sea bottom. This study focuses on internal-wave-induced particle transport in the vicinity of (almost) vertical walls. We report a series of laboratory experiments revealing that particles sinking slowly through a monochromatic internal wave beam experience significant horizontal advection. Extending the theoretical analysis by Beckebanze et al. (J. Fluid Mech., vol. 841, 2018, pp. 614-635), we attribute the observed particle advection to a peculiar and previously unrecognized streaming mechanism in the stratified boundary layer originating at the lateral walls. This vertical boundary layer streaming mechanism is most efficient for significantly inclined wave beams, when vertical and horizontal velocity components are of comparable magnitude. We find good agreement between our theoretical prediction and experimental results

Particle transport induced by internal wave beam streaming in lateral boundary layers

Quantifying the physical mechanisms responsible for the transport of sediments, nutrients and pollutants in the abyssal sea is a long-standing problem, with internal waves regularly invoked as the relevant mechanism for particle advection near the sea bottom. This study focuses on internal-wave-induced particle transport in the vicinity of (almost) vertical walls. We report a series of laboratory experiments revealing that particles sinking slowly through a monochromatic internal wave beam experience significant horizontal advection. Extending the theoretical analysis by Beckebanze et al. (J. Fluid Mech., vol. 841, 2018, pp. 614–635), we attribute the observed particle advection to a peculiar and previously unrecognized streaming mechanism in the stratified boundary layer originating at the lateral walls. This vertical boundary layer streaming mechanism is most efficient for significantly inclined wave beams, when vertical and horizontal velocity components are of comparable magnitude. We find good agreement between our theoretical prediction and experimental results.</jats:p