Biodegradable Biocomposite of Starch Films Cross-Linked with Polyethylene Glycol Diglycidyl Ether and Reinforced by Microfibrillated Cellulose.

Biopolymers are biodegradable and renewable and can significantly reduce environmental impacts. For this reason, biocomposites based on a plasticized starch and cross-linker matrix and with a microfibrillated OCC cardboard cellulose reinforcement were developed. Biocomposites were prepared by suspension casting with varied amounts of microfibrillated cellulose: 0, 4, 8, and 12 wt%. Polyethylene glycol diglycidyl ether (PEGDE) was used as a cross-linking, water-soluble, and non-toxic agent. Microfibrillated cellulose (MFC) from OCC cardboard showed appropriate properties and potential for good performance as a reinforcement. In general, microfiber incorporation and matrix cross-linking increased crystallization, reduced water adsorption, and improved the physical and tensile properties of the plasticized starch. Biocomposites cross-linked with PEGDE and reinforced with 12 wt% MFC showed the best properties. The chemical and structural changes induced by the cross-linking of starch chains and MFC reinforcement were confirmed by FTIR, NMR, and XRD. Biodegradation higher than 80% was achieved for most biocomposites in 15 days of laboratory compost.

Jasmonic and Salicylic Acids Enhance Biomass, Total Phenolic Content, and Antioxidant Activity of Adventitious Roots of Acmella radicans (Jacq.) R.K. Jansen Cultured in Shake Flasks.

Acmella radicans (Asteraceae) is a plant native to America. Despite it having medicinal attributes, studies on its phytochemical properties are scarce, and biotechnological studies do not exist for this species. In this study, we established an adventitious root culture from A. radicans internodal segments in shake flasks with indole-3-butyric acid (IBA), and then elicited it with jasmonic acid (JA) and salicylic acid (SA). The total phenolic content and antioxidant activity were evaluated, and a comparison was made using in vitro plantlets and wild plants. Internodal segments with 0.1 mg/L IBA showed 100% root induction and exhibited better growth after transfer to shake flasks with MS liquid culture medium. JA had a significant effect on biomass increase compared to unelicited roots, mainly with 50 µM JA (28%), while SA did not show significant results. Root elicited with 100 µM (SA and JA) showed a 0.34- and 3.9-fold increase, respectively, in total phenolic content (TPC) compared to the control. The antioxidant activity was also significant, and a lower half-maximal inhibitory concentration (IC50) was observed as the AJ concentration increased. Roots elicited with AJ (100 µM) exhibited high antioxidant activity with DPPH (IC50 = 9.4 µg/mL) and ABTS (IC50 = 3.3 µg/mL) assays; these values were close to those for vitamin C (IC50 = 2.0 µg/mL). The TPC and antioxidant activity of in vitro plants and root cultured in shake flasks showed the lowest values in most cases; even the root cultures without elicitation were better than those of a wild plant. In this study, we demonstrated that A. radicans root culture is capable of producing secondary metabolites, while its production and antioxidant activity can be enhanced using jasmonic acid.

In Vivo Modification of Microporous Structure in Bacterial Cellulose by Exposing Komagataeibacter xylinus Culture to Physical and Chemical Stimuli.

Bacterial cellulose (BC) samples were obtained in a static culture of K. xylinus under the effect of a low-intensity magnetic field, UV light, NaCl, and chloramphenicol. The effect of such stimuli on the amount of BC produced and its production rate, specific area, pore volume, and pore diameter were evaluated. The polysaccharide production was enhanced 2.28-fold by exposing K. xylinus culture to UV light (366 nm) and 1.7-fold by adding chloramphenicol (0.25 mM) to the medium in comparison to BC control. All the stimuli triggered a decrease in the rate of BC biosynthesis. BC membranes were found to be mesoporous materials with an average pore diameter from 21.37 to 25.73 nm. BC produced under a magnetic field showed the lowest values of specific area and pore volume (2.55 m2 g-1 and 0.024 cm3 g-1), while the BC synthesized in the presence of NaCl showed the highest (15.72 m2 g-1 and 0.11 cm3 g-1). FTIR spectra of the BC samples also demonstrated changes related to structural order. The rehydration property in these BC samples is not mainly mediated by the crystallinity level or porosity. In summary, these results support that BC production, surface, and structural properties could be modified by manipulating the physical and chemical stimuli investigated.

A Simplified Method of Synthesis to Obtain Zwitterionic Cellulose under Mild Conditions with Active Ionic Moieties.

A simplified procedure to synthesize zwitterionic cellulose by means of N-protected aspartic anhydride under mild conditions was developed. The preparation of modified cellulose samples was carried out under heterogeneous, aqueous conditions by reacting NH4OH-activated cellulose with aspartic anhydrides N-protected with trifluoroacetyl (TFAc) and carbobenzyloxy (Cbz). Modified cellulose samples Cel-Asp-N-TFAc and Cel-Asp-N-Cbz were characterized by Fourier Transform Infrared (FTIR) and 13C solid state Nuclear Magnetic Resonance (NMR) spectroscopy. The functionalization degree of each cellulose sample was determined by the 13C NMR signal integration values corresponding to the cellulose C1 vs. the Cα of the aspartate residue and corroborated by elemental analysis. In agreement, both analytical methods averaged a grafting degree of 20% for Cel-Asp-N-TFAc and 16% for Cel-Asp-N-Cbz. Conveniently, Cel-Asp-N-TFAc was concomitantly partially N-deprotected (65%) as determined by the ninhydrin method. The zwitterion character of this sample was confirmed by a potentiometric titration curve and the availability of these amino acid residues on the cellulose was inspected by adsorption kinetics method with a 100 mg L-1 cotton blue dye solution. In addition, the synthesis reported in the present work involves environmentally related advantages over previous methodologies developed in our group concerning to zwitterionic cellulose preparation.

XRD and solid state 13C-NMR evaluation of the crystallinity enhancement of 13C-labeled bacterial cellulose biosynthesized by Komagataeibacter xylinus under different stimuli: A comparative strategy of analyses.

The production and crystallinity of 13C bacterial cellulose (BC) was examined in static culture of Komagataeibacter xylinus with different chemical and physical stimuli: the addition of NaCl or cloramphenicol as well as exposure to a magnetic field or to UV light. Crystalline BC biosynthesized under each stimulus was studied by XRD and solid state 13C NMR analyses. All treatments produced BC with enhanced crystallinity over 90% (XRD) and 80% (NMR) compared to the control (83 and 76%, respectively) or to Avicel (77 and 62%, respectively). The XRD data indicated that the crystallite size was 80-85 Å. Furthermore, changes on the allomorphs (Iα and Iß) ratio tendency of BC samples addressed to the stimuli were estimated using the C4 signal from 13C NMR data. These results showed a decrease of the allomorph Iα (3%) when BC was biosynthesized with UV light and chloramphenicol compared to control (58.79%). In contrast, the BC obtained with NaCl increased up to 60.31% of the Iα allomorph ratio.

Chiral Imidazolium-Functionalized Au Nanoparticles: Reversible Aggregation and Molecular Recognition.

Gold nanoparticles (AuNPs) stabilized by imidazolium salts derived from amino acids [glycine (1), rac-alanine (2), l-phenylalanine (3), and rac-methionine (4)] were prepared. The AuNPs were stabilized the most by 4, which kept the particles dispersed in water for months at pH > 5.5. These AuNPs exhibited a well-defined absorption band at 517 nm and had an average particle size of 11.21 ± 0.07 nm. The 4-AuNPs were reversibly aggregated by controlling the pH of the solution. Chiral R,R-4-AuNPs and S,S-4-AuNPs were synthesized, and the chiral environment on the nanoparticle surface was confirmed using circular dichroism; these nanoparticles exhibited a molecular recognition of chiral substrates. Furthermore, they showed potential for separating racemic mixtures when supported on a layered double hydroxide.

Bio-composites of cassava starch-green coconut fiber: part II-Structure and properties.

Development of any new material requires its complete characterization to find potential applications. In that direction, preparation of bio-composites of cassava starch containing up to 30 wt.% green coconut fibers from Brazil by thermal molding process was reported earlier. Their characterization regarding physical and tensile properties of both untreated and treated matrices and their composites were also reported. Structural studies through FTIR and XRD and thermal stability of the above mentioned composites are presented in this paper. FT-IR studies revealed decomposition of components in the matrix; the starch was neither chemically affected nor modified by either glycerol or the amount of fiber. XRD studies indicated increasing crystallinity of the composites with increasing amount of fiber content. Thermal studies through TGA/DTA showed improvement of thermal stability with increasing amount of fiber incorporation, while DMTA showed increasing storage modulus, higher glass transition temperature and lower damping with increasing fiber content. Improved interfacial bonding between the matrix and fibers could be the cause for the above results.