Amphiphilic cationic polymethacrylates: synthesis, characterization and interactions with cellulose

Amphiphilic cationic co-polymers, containing poly([2-(methacryloyloxy)ethyl] trimethyl ammonium iodide) (polyMETAI) or poly[2-(dimethylamino) ethyl methacrylate] (PDM) segment, were synthesized through two different main routes. Block co-polymers containing poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) were synthesized with oxyanionic polymerization, whereas radical polymerization was used to obtain statistical co-polymers with stearyl methacrylate (SMA) and fluorodecyl methacrylate (FMA). The melt and thermal transition properties of the polymers were studied with dynamic scanning calorimetry and rheometry. PDM decreased crystallinity of the polymer and increased the melt strength of the polymers. The solution properties were studied with a surface tension measurement, with dynamic light scattering equipment, and with rheometry. Polymers containing highly hydrophobic segments, such as stearyl, formed charge stabilized aggregates in a water solution, whereas polymers with a less hydrophobic block, such as PEO, formed a micellar structure. The suitability of the prepared polymers, as well as a set of commercial polymers, on cellulose fiber systems was studied. The polymers containing a cationic segment formed permanent adhesion on the anionic surface, and strong bonding with the cellulose fibers. The mechanical strength of the cellulose fiber sheets was increased more with polymers containing cationic segments than the ones with corresponding nonionic segments. Strain hardening behaviour was introduced into the fiber-polymer sheets that did not contain cationic segments and the bonding between the fiber and the polymer was weak enough. A mechanically strong cellulose fiber network could also be prepared with a hydrophobic cationic polymer, but the strength was decreased with the high density of the hydrophobic side group in the polymer. The polymers containing a highly hydrophobic segment formed a thin layer coating on the paper surface and a small amount of polymer was enough for a complete thin layer coverage of the surface. Additionally, the higher amount of the polymer did not change the chemical or physical properties of the surface, which supported the assumption of a nanolayer formation

Xylo- and cello-oligosaccharide oxidation by gluco-oligosaccharide oxidase from Sarocladium strictum and variants with reduced substrate inhibition

Peer reviewe

Effect of cationic polymethacrylates on the rheology and flocculation of microfibrillated cellulose

Peer reviewe

Open Access

Xylo- and cello-oligosaccharide oxidation by gluco-oligosaccharide oxidase from Sarocladium strictum and variants with reduced substrate inhibitio

Xylo- and cello-oligosaccharide oxidation by gluco-oligosaccharide oxidase from Sarocladium strictumand variants with reduced substrate inhibition

Abstract Background The oxidation of carbohydrates from lignocellulose can facilitate the synthesis of new biopolymers and biochemicals, and also reduce sugar metabolism by lignocellulolytic microorganisms, reserving aldonates for fermentation to biofuels. Although oxidoreductases that oxidize cellulosic hydrolysates have been well characterized, none have been reported to oxidize substituted or branched xylo-oligosaccharides. Moreover, this is the first report that identifies amino acid substitutions leading to GOOX variants with reduced substrate inhibition. Results The recombinant wild type gluco-oligosaccharide oxidase (GOOX) from the fungus Sarocladium strictum, along with variants that were generated by site-directed mutagenesis, retained the FAD cofactor, and showed high activity on cello-oligosaccharide and xylo-oligosaccharides, including substituted and branched xylo-oligosaccharides. Mass spectrometric analyses confirmed that GOOX introduces one oxygen atom to oxidized products, and 1H NMR and tandem mass spectrometry analysis confirmed that oxidation was restricted to the anomeric carbon. The A38V mutation, which is close to a predicted divalent ion-binding site in the FAD-binding domain of GOOX but 30 Å away from the active site, significantly increased the kcat and catalytic efficiency of the enzyme on all oligosaccharides. Eight amino acid substitutions were separately introduced to the substrate-binding domain of GOOX-VN (at positions Y72, E247, W351, Q353 and Q384). In all cases, the Km of the enzyme variant was higher than that of GOOX, supporting the role of corresponding residues in substrate binding. Most notably, W351A increased Km values by up to two orders of magnitude while also increasing kcat up to 3-fold on cello- and xylo-oligosaccharides and showing no substrate inhibition. Conclusions This study provides further evidence that S. strictum GOOX has broader substrate specificity than the enzyme name implies, and that substrate inhibition can be reduced by removing aromatic side chains in the -2 binding subsite. Of the enzyme variants, W351A might be particularly advantageous when oxidizing oligosaccharides present at high substrate concentrations often experienced in industrial processes

A Systematic Study of Noncross-linking Wet Strength Agents

Cellulosic fibers are inherently hydrophilic, and the modification of them to withstand moisture is important both commercially and scientifically. The usual methods are based on the cross-linking chemistry of reactive groups such as epichlorohydrins. Here, we present that it is possible to attain paper with wet strength from a combination of polymers that lack cross-linking chemistry, namely, carboxymethyl cellulose (CMC) and Polybrene. To accomplish this, we first altered the surface charge of the fibers by adsorption of CMC. Subsequent adsorption of Polybrene, forming the fibers as paper sheets, and drying yielded paper with wet strength properties. The wet strengthening was further investigated by (i) varying the molecular weight of the CMC, (ii) varying the cationic polyelectrolyte, and (iii) synthesizing polymers called ionenes to study the structural properties behind the wet strength of Polybrene. The results showed that (i) drying was necessary to obtain wet strength, (ii) wet strength seemed to be a surface effect, (iii) high <i>M</i>_w CMC played an important role in the development of wet strength, and (iv) only asymmetric ionenes ([3,6] and [6,12]-ionenes) could attain wet strength while symmetric [3,3] and [6,6]-ionenes failed to show wet strength properties

A Systematic Study of Noncross-linking Wet Strength Agents

Cellulosic fibers are inherently hydrophilic, and the modification of them to withstand moisture is important both commercially and scientifically. The usual methods are based on the cross-linking chemistry of reactive groups such as epichlorohydrins. Here, we present that it is possible to attain paper with wet strength from a combination of polymers that lack cross-linking chemistry, namely, carboxymethyl cellulose (CMC) and Polybrene. To accomplish this, we first altered the surface charge of the fibers by adsorption of CMC. Subsequent adsorption of Polybrene, forming the fibers as paper sheets, and drying yielded paper with wet strength properties. The wet strengthening was further investigated by (i) varying the molecular weight of the CMC, (ii) varying the cationic polyelectrolyte, and (iii) synthesizing polymers called ionenes to study the structural properties behind the wet strength of Polybrene. The results showed that (i) drying was necessary to obtain wet strength, (ii) wet strength seemed to be a surface effect, (iii) high <i>M</i>_w CMC played an important role in the development of wet strength, and (iv) only asymmetric ionenes ([3,6] and [6,12]-ionenes) could attain wet strength while symmetric [3,3] and [6,6]-ionenes failed to show wet strength properties