Methylcellulose fibrils: a mini review

This review covers the recently discovered methylcellulose (MC) fibrils and their impact on MC thermogelation and overall gel strength. The thermogelation of MC aqueous solutions has been studied for nearly 100 years, but it has only recently been attributed to fibril formation at elevated temperatures. The assembly of a fibrillar network explains the general features of MC gels: the unusually high modulus, the turbidity, and the nonlinear rheological behavior at high strains. Recent scattering, atomic force microscopy (AFM) and cryogenic transmission electron microscopy (cryo‐TEM) experimental efforts have led to critical discoveries about the fibril structure. MC fibrils are 60% water by volume when in solution. The length of the fibrils, especially for shorter chains, is closely correlated with the MC chain contour length. On the other hand, the fibril radius does not depend on the temperature, molecular weight or concentration of MC chains but does seem to be correlated with chain stiffness. The discovery of MC fibrils represents a significant departure from the entanglement of polymer chains and localized phase separation based physical model of MC gelation, opens new questions about the mechanism of fibril formation and presents new pathways for stimulus responsive material design. © 2019 Society of Chemical Industry     

Increase in bioethanol production yield from triticale by simultaneous saccharification and fermentation with application of ultrasound

BACKGROUND: Bioethanol produced from renewable biomass, such as sugar, starch or lignocellulosic materials, is one of the alternative energy resources that is environmentally friendly. Triticale crops have a high yield as well as a high starch content and amylolytic enzyme activity and are therefore considered to be ideal for bioethanol production. RESULTS: This study examined the feasibility of ultrasound pretreatment to enhance the release of fermentable sugars from triticale meal during pretreatment and consequently increase bioethanol yield in the simultaneous saccharification and fermentation (SSF) process by Saccharomyces cerevisiae yeast. Ultrasonic pretreatment effectively increased the glucose and maltose content after liquefaction by 15.71% and 52.57%, respectively, compared with the untreated control sample under determined optimal conditions of sonication (5 min, 60 °C). The ultrasound pretreatment consequently improved bioethanol production during SSF processing since the bioethanol content was increased by 10.89%. CONCLUSION: Taking into consideration significant process parameters obtained in the SSF process of triticale meal with ultrasound pretreatment at 60 °C, the process time may be reduced from 72 to 48 h. At that point of the SSF, maximum bioethanol content of 9.55% (w/v), bioethanol yield of 0.43 g g^?1 of triticale starch, and percentage of the theoretical bioethanol yield of 84.56% were achieved. Copyright © 2011 Society of Chemical Industry     

From Native Starch to Hydrophilic and Hydrophobic Products: A Catalytic Approach

Two new catalytic processes have been developed to modify the hydrophilic/hydrophobic properties of insoluble, native starch. Soluble metal catalysts under proper reaction conditions were used to prepare tailor-made products suitable for various technological applications. Selective, clean oxidation of native starch by hydrogen peroxide in the presence of 0.003–0.016 mol% of iron tetrasulfonatophthalocyanine catalyst (FePcS) provided hydrophilic starch having 0.5–7 carboxyl and 1–11 carbonyl functions per 100 AGU (anhydroglucose units). The oxidation reaction was performed either with starch suspended in catalyst solution or by impregnation of starch powder with catalyst solution (dry process). Only small amounts of water, hydrogen peroxide and cheap FePcS catalysts were needed in the dry process to achieve a successful modification of starch in one step with almost quantitative yields. Hydrophobic starches with degree of substitution ranging from 0.08 to 0.43 per AGU have been prepared by butadiene telomerization in the presence of soluble palladium complexes. The best results in terms of degree of substitution at 50 °C have been obtained with Pd/TPPTS catalyst. The telomerization of starch with isoprene was also demonstrated. The etherified starch can be further transformed by hydrogenation using Wilkinson-type catalyst in EtOH/H₂O.     

Non-catalyzed addition of secondary phosphine chalcogenides to divinyl chalcogenides under solvent-free conditions

Secondary phosphine chalcogenides, R₂PX (R═(CH₂)₂Ph, Ph; X?=?S, Se), react with divinyl chalcogenides, (CH₂═CH)₂Y (Y?=?S, Se, Te), at the 2:1 molar ratio (80–82°C, 56–80?h) in the absence of both catalysts (initiators) and solvents to quantitatively afford the corresponding anti-Markovnikov diadducts. Even at the equimolar reactant ratio, the diadducts are the major products, though monoadducts are also formed. When Y?=?Te, vinylphosphine chalcogenides and metal Te are obtained, thus showing that divinyl telluride behaves as the vinylating agent.     

Novel allene oxide synthase products formed via Favorskii-type rearrangement: mechanistic implications for 12-oxo-10,15-phytodienoic acid biosynthesis

The allene oxide synthase (AOS) pathway is widespread in plants. Its products, such as cyclopentenone 12-oxo-10,15-phytodienoic acid (12-oxo-PDA) and related jasmonates, play important biological roles in plants. We found that 12-oxo-PDA in some plant tissues co-occur with an unknown minor oxylipin 1. In vitro incubations of AOSs with α-linolenic acid 13(S)-hydroperoxide reliably afforded 1 along with 12-oxo-PDA and α-ketol. A similar oxylipin 3 was formed during the AOS conversions of γ-linolenic acid 9(S)-hydroperoxide. Linoleic acid hydroperoxides formed neither products similar to 1 and 3 nor cyclopentenones. Oxylipins 1 and 3 were purified and identified as the products of Favorskii-type rearrangement, (2'Z,4Z)-2-(2'-pentenyl)-4-tridecene-1,13-dioic acid and (2'Z,4Z)-2-(2'-octenyl)-4-decene-1,10-dioic acid, respectively. Detection of Favorskii products 1 and 3 demonstrates that cyclopropanones are short-lived AOS products along with allene oxides. The observed parallels between the Favorskii product 1 and 12-oxo-PDA formation suggests that cyclopropanone is either a byproduct or a precursor of 12-oxo-PDA.     

Melt spinning and characterization of hollow fibers from poly(4-methyl-1-pentene)

In this article, the melt spinning behavior of poly(4-methyl-1-pentene) (PMP) hollow fibers (HF) is examined. The melt spinning trials are carried out on a pilot scale melt spinning plant with different settings while a 10-hole 2c-shaped spinneret is used. It is found that the winding speed mainly affects the outer fiber diameter. The influence of different melt spinning parameters is investigated, in particular temperatures, take-up velocities, and the use of quench air. For this purpose, the shape and crystalline structure of the fibers are analyzed using a light microscope, a scanning electron microscope, and wide-angle X-ray scattering. The shape of the fibers is mainly influenced by the temperature settings in the melt spinning process. As a reasonable lower limit, a melt spinning temperature of 280°C is identified. Concerning the crystallinity, a saturation going along with a slight reduction of the polymer chain orientation is observed at elevated take-up velocities.     

Development of antifouling ultrafiltration PES membranes for concentration of hemicellulose

A new approach for one-stage facile membrane modification during non-solvent induced phase separation (NIPS)-process is proposed. The novelty of this study is that cheap and commercially available anionic high molecular polyacrylamide-based flocculant (AHMPF) is applied for the first time as an additive to coagulation bath (CB). The series of polyethersulfone membranes were prepared using 0.05–0.3 wt% AHMPF aqueous solution as CB at different temperatures (25–50°C) via NIPS. The effect of AHMPF concentration on the structure, composition and hydrophilicity of membranes was investigated. The separation and antifouling performance were evaluated during filtration of bovine serum albumin (BSA) solution and thermomechanical pulp mills process water (ThMP) in order to concentrate hemicellulose. The successful immobilization of AHMPF into the structure of membranes selective layer (not bottom layer) was confirmed by FTIR spectroscopy. It was established that despite the similar rejection of hemicellulose (88.8–93%) and lignin (20–21.4), modified membranes demonstrate 3–8 times higher flux and 2 times higher FRR (43.8% for reference membrane and 86.5% for modified one) in ThMP ultrafiltration. The developed membrane was found to be highly efficient in hemicellulose concentration and purification in pulp industry.     

Targeting of Deregulated Wnt/β-Catenin Signaling by PRI-724 and LGK974 Inhibitors in Germ Cell Tumor Cell Lines

The majority of patients with testicular germ cell tumors (GCTs) can be cured with cisplatin-based chemotherapy. However, for a subset of patients present with cisplatin-refractory disease, which confers a poor prognosis, the treatment options are limited. Novel therapies are therefore urgently needed to improve outcomes in this challenging patient population. It has previously been shown that Wnt/β-catenin signaling is active in GCTs suggesting that its inhibitors LGK974 and PRI-724 may show promise in the management of cisplatin-refractory GCTs. We herein investigated whether LGK-974 and PRI-724 provide a treatment effect in cisplatin-resistant GCT cell lines. Taking a genoproteomic approach and utilizing xenograft models we found the increased level of β-catenin in 2 of 4 cisplatin-resistant (CisR) cell lines (TCam-2 CisR and NCCIT CisR) and the decreased level of β-catenin and cyclin D1 in cisplatin-resistant NTERA-2 CisR cell line. While the effect of treatment with LGK974 was limited or none, the NTERA-2 CisR exhibited the increased sensitivity to PRI-724 in comparison with parental cell line. Furthermore, the pro-apoptotic effect of PRI-724 was documented in all cell lines. Our data strongly suggests that a Wnt/β-catenin signaling is altered in cisplatin-resistant GCT cell lines and the inhibition with PRI-724 is effective in NTERA-2 CisR cells. Further evaluation of Wnt/β-catenin pathway inhibition in GCTs is therefore warranted.     

Kinetics of formation of boundary lubricating film in zone of facing–tool contact under metal cutting

Tribological processes that occur in the zone of the facing–tool contact can be satisfactorily described using a three-zone model in which zones of adhesion, seizure, and friction are distinguished. An expression that relates the coefficient of friction under cutting to the distribution of the zones of friction over the surface of contact has been obtained, causes for the origination of the zone of adhesion have been analyzed, and the shear strength of boundary films has been estimated. A model that describes the kinetics of the formation of a boundary lubricating film in the zone of friction with account for the dimensions and the shape of surfactant molecules, as well as the concentration of surfactants, has been developed. The results of the calculations have shown good agreement with the experimental data.