Influence of citric acid on thermoplastic wheat flour/poly (lactic acid) blends. II. Barrier properties and water vapor sorption isotherms

The effects of citric acid on wheat flour/glycerol/poly(lactic) acid (PLA) blends prepared by one-step twin-screw extrusion have been studied to improve barrier properties of starch based materials. A series of injected samples were produced from prepared compounds with varying ratio (0-20 part) of citric acid. The effects of citric acid on the water vapor permeability, oxygen permeability and water solubility in the film were then investigated. The barrier properties results proved that citric acid behaves as compatibilizing agent between starch and PLA phases for ratios between 0 and 10 parts. When the added amount exceeds 10 parts, CA acted as a plasticizer and/or promoted the hydrolysis of the starch glycosidic bonds

Whole proteome analyses on Ruminiclostridium cellulolyticum show a modulation of the cellulolysis machinery in response to cellulosic materials with subtle differences in chemical and structural properties

Lignocellulosic materials from municipal solid waste emerge as attractive resources for anaerobic digestion biorefinery. To increase the knowledge required for establishing efficient bioprocesses, dynamics of batch fermentation by the cellulolytic bacterium Ruminiclostridium cellulolyticum were compared using three cellulosic materials, paper handkerchief, cotton discs and Whatman filter paper. Fermentation of paper handkerchief occurred the fastest and resulted in a specific metabolic profile: it resulted in the lowest acetate-to-lactate and acetate-to-ethanol ratios. By shotgun proteomic analyses of paper handkerchief and Whatman paper incubations, 151 proteins with significantly different levels were detected, including 20 of the 65 cellulosomal components, 8 non-cellulosomal CAZymes and 44 distinct extracytoplasmic proteins. Consistent with the specific metabolic profile observed, many enzymes from the central carbon catabolic pathways had higher levels in paper handkerchief incubations. Among the quantified CAZymes and cellulosomal components, 10 endoglucanases mainly from the GH9 families and 7 other cellulosomal subunits had lower levels in paper handkerchief incubations. An in-depth characterization of the materials used showed that the lower levels of endoglucanases in paper handkerchief incubations could hypothetically result from its lower crystallinity index (50%) and degree of polymerization (970). By contrast, the higher hemicellulose rate in paper handkerchief (13.87%) did not result in the enhanced expression of enzyme with xylanase as primary activity, including enzymes from the xyl-doc cluster. It suggests the absence, in this material, of molecular structures that specifically lead to xylanase induction. The integrated approach developed in this work shows that subtle differences among cellulosic materials regarding chemical and structural characteristics have significant effects on expressed bacterial functions, in particular the cellulolysis machinery, resulting in different metabolic patterns and degradation dynamics.This work was supported by a grant [R2DS 2010-08] from Conseil Regional d'Ile-de-France through DIM R2DS programs (http://www.r2ds-ile-de-france.com/). Irstea (www.irstea.fr/) contributed to the funding of a PhD grant for the first author. The funders provided support in the form of salaries for author [NB], funding for consumables and laboratory equipment, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Omics Services provided support in the form of salaries for authors [VS, MD], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors [NB, VS, MD] are articulated in the 'author contributions' section.info:eu-repo/semantics/publishedVersio

A review on development and application of plant-based bioflocculants and grafted bioflocculants

Flocculation is extensively employed for clarification through sedimentation. Application of eco-friendly plant-based bioflocculants in wastewater treatment has attracted significant attention lately with high removal capability in terms of solids, turbidity, color, and dye. However, moderate flocculating property and short shelf life restrict their development. To enhance the flocculating ability, natural polysaccharides derived from plants are chemically modified by inclusion of synthetic, nonbiodegradable monomers (e.g., acrylamide) onto their backbone to produce grafted bioflocculants. This review is aimed to provide an overview of the development and flocculating efficiencies of plant-based bioflocculants and grafted bioflocculants for the first time. Furthermore, the processing methods, flocculation mechanism, and the current challenges are discussed. All the reported studies about plant-derived bioflocculants are conducted under lab-scale conditions in wastewater treatment. Hence, the possibility to apply natural bioflocculants in food and beverage, mineral, paper and pulp, and oleo-chemical and biodiesel industries is discussed and evaluated

Recent advances and perspectives on starch nanocomposites for packaging applications

Starch nanocomposites are popular and abundant materials in packaging sectors. The aim of this work is to review some of the most popular starch nanocomposite systems that have been used nowadays. Due to a wide range of applicable reinforcements, nanocomposite systems are investigated based on nanofiller type such as nanoclays, polysaccharides and carbonaceous nanofillers. Furthermore, the structures of starch and material preparation methods for their nanocomposites are also mentioned in this review. It is clearly presented that mechanical, thermal and barrier properties of plasticised starch can be improved with well-dispersed nanofillers in starch nanocomposites

Understanding the mechanisms involved in shape memory starch: Macromolecular orientation, stress recovery and molecular mobility

cited By 20International audienceThe effect of a deformation near and above the glass transition on macromolecular orientation, residual stress, and molecular mobility was investigated on amorphous stimuli-responsive starch. The recovery stress, linked to the residual stress in the temporary shape, evolves linearly with the macromolecular orientation. Increasing the deformation temperature decreases the residual stress and the macromolecular orientation. This also leads to a higher glass transition temperature induced by a decrease in molecular mobility. The local structures potentially involved in orientation and stress recovery and their behavior during deformation at different temperatures are discussed. © 2011 American Chemical Society

Accumulation of multiple-repeat starch-binding domains (SBD2-SBD5) does not reduce amylose content of potato starch granules

This study investigates whether it is possible to produce an amylose-free potato starch by displacing the amylose enzyme, granule-bound starch synthase I (GBSSI), from the starch granule by engineered, high-affinity, multiple-repeat family 20 starch-binding domains (SBD2, SBD3, SBD4, and SBD5). The constructs were introduced in the amylose-containing potato cultivar (cv. Kardal), and the starches of the resulting transformants were compared with those of SBD2-expressing amylose-free (amf) potato clones. It is shown that a correctly sized protein accumulated in the starch granules of the various transformants. The amount of SBD accumulated in starch increased progressively from SBD to SBD3; however, it seemed as if less SBD4 and SBD5 was accumulated. A reduction in amylose content was not achieved in any of the transformants. However, it is shown that SBDn expression can affect physical processes underlying granule assembly, in both genetic potato backgrounds, without altering the primary structure of the constituent starch polymers and the granule melting temperature. Granule size distribution of the starches obtained from transgenic Kardal plants were similar to those from untransformed controls, irrespective of the amount of SBDn accumulated. In the amf background, granule size is severely affected. In both the Kardal and amf background, apparently normal oval-shaped starch granules were composed of multiple smaller ones, as evidenced from the many ¿Maltese crosses¿ within these granules. The results are discussed in terms of different binding modes of SBD