Hydrogen photocatalytic production from the self-assembled films of PAH/PAA/TiO2 supported on bacterial cellulose membranes

The issues related to renewable energy sources is a matter of great worldwide appeal due to the increasing energy demand, instability in oil prices and environmental problems. In this context, the purpose of this study was to prepare self-assembled films of polyallylamine hydrochloride and poly (acrylic acid) supported onto bacterial cellulose membranes by a layer-by-layer approach with titanium dioxide (TiO₂) nanoparticles and different concentrations of gold for application in hydrogen gas (H₂) production by photocatalysis. The influence of the gold concentration and the presence and size of the gold nanoparticles (Au NPs), as well as the surface and thickness of the films on H₂ production was investigated. The results showed that the film, prepared with a lower concentration of gold, presented the smallest Au NPs and, therefore, greater contact with the TiO₂ nanoparticle surfaces, producing more H₂. By analyzing the variation in all the experimental parameters used in the preparation of the films, it can be concluded that the best H₂ production achieved was 29.12 μmol h^?1 cm².     

Effect of processing conditions on wood and glass fiber length attrition during twin screw composite compounding

In this study, we compare the effect of twin-screw extrusion processing on the attrition of wood fibers (WFs) with glass fiber. The effects of process variables and screw design on fiber length were investigated by performing a range of dead-stop experiments where the extruder was stopped, opened-up, and compound removed from the screw elements. Fibers, chemically extracted from the polypropylene matrix, were analyzed for length and width using a commercial fiber analyzer. It was found that WF length attrition and composite properties were less affected by screw design and twin-screw processing conditions (feed rate and screw speed) than glass fiber. Length weighted fiber length and X50 length (a measure used in particle size analysis) were equally correlated with process conditions and composite performance for both fiber types. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48551.     

Synthesis and characterization of cellulose nanowhisker-reinforced-poly(ε-caprolactone) scaffold for tissue-engineering applications

Poly(ε-caprolactone) (PCL) is a bioresorbable and biocompatible polymer with assorted medical applications. However, remarkable hydrophobicity and nonosteoconductivity have stood as a barrier to limit its applications. The present study aims to modify the bulk characteristics of PCL to develop a polymeric scaffold with adequate structural and mechanical properties to support regenerated tissues. For this purpose, functionalized bacterial cellulose nanowhiskers (BCNW-g-βCD-PCL₂₀₀₀) are synthesized. Reinforcing PCL matrix with 4 wt % of the nanowhiskers resulted in a bionanocomposite with promoted bulk properties. Compared to neat PCL, the obtained bionanocomposite shows improvements of 115 and 51% in tensile strength and Young's modulus, respectively; 20% increase in hydrophilicity; 7% increase in degradation rate; and 6% decrease in crystallinity. Gas foaming/combined particulate leaching technique is used to develop highly porous structures of 86–95% porosity with interconnected macropores of mean pore diameters of 250–420 μm. Porous scaffolds showed compression modulus values of 5.3–9.1 MPa and would have promising applications in regenerative medicine. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48481.     

固态发酵产酶反应中体系传热传质行为分析

固态发酵是纤维素类生物质转化的有效途径,具有用水量少、容积产率高等优点。固态发酵生产纤维素酶一般是液态发酵酶产量的近3倍,可大幅降低酶的生产成本。在固态发酵过程,微生物在缺水环境中生长,发酵底物和接种物之间存在异质性,导致发酵热量分布不均匀、发酵过程氧气与中间产物不易扩散等问题。基于此,重点对固态发酵反应中体系传热传质方式及其影响因素进行了分析,并探讨其强化方法。根据传热方式,总结了发酵罐适用的导热微分方程及传热模拟方法,并分析气泡和颗粒基质中的传质过程及其限速步骤以及解决传质限速的途径。反应体系传热传质机理研究可促进固态发酵技术产业化应用进程。该研究可为有机废弃物固态发酵技术研究及应用提供一定的理论和技术支持。     

氨基磺酸盐型水性醋酸纤维乳液的制备与性能

采用乙二胺基乙磺酸钠(AAS)作为亲水剂,在二月桂酸二丁基锡(DBTDL)的催化下,通过异佛尔酮二异氰酸酯(IPDI)将亲水基引入二醋酸纤维(CA)分子中,制得了一种氨基磺酸盐型水性醋酸纤维乳液(SWCA)。利用FTIR、DLS、黏度计、TEM、SEM、接触角测量仪、XRD、TGA,对SWCA结构及涂膜性能进行表征。考察了IPDI与AAS物质的量比对SWCA乳液粒径、黏度、涂膜表观形貌及耐水性的影响。结果表明:当n(IPDI)∶n(AAS)=1.1∶1时,乳液最稳定,微观形态呈水包油型(O/W)核壳结构,乳液粒径和分散系数(PDI)最小,分别为128nm和0.112,此时乳液表观黏度最大,为73.5m Pa·s,所成涂膜致密平整,接触角可达110.2°±2°,表现出明显的疏水性;此外,与二醋酸纤维相比,SWCA涂膜结晶性减弱,呈微晶态或次晶态结构,且具有较好的耐热性。     

Encapsulation and characterisation of grape seed proanthocyanidin extract using sodium alginate and different cellulose derivatives

Grape seed proanthocyanidin extract (GSPE) has health benefits. However, these phenolic compounds undergo degradation reactions and have undesirable sensorial characteristics. GSPE was encapsulated using sodium alginate (SA), SA-methyl cellulose (MC) and SA-hydroxypropyl methylcellulose (HPMC) for promoting controlled release, pH stability, temperature and storage period tolerance of GSPE. The microcapsules were characterised using scanning electron microscopy (SEM) and Fourier transform infra-red (FTIR) analysis. The SA-MC and SA-HPMC microcapsules appeared to have a more compact surface than SA-alone microcapsules. FTIR analysis indicated successful immobilisation of GSPE into the polymeric microcapsules. Moreover, the SA-MC and SA-HPMC microcapsules showed higher thermal stability. The microcapsules showed a relatively higher amount of released GSPE at a pH above six than at a lower pH. The SA-MC and SA-HPMC microcapsules could be used to retain more GSPE content in the gastric phase and to release it in the intestinal phase for possible absorption. Furthermore, after 28 days of storage at 25 °C, the GSPE retention rate of the microcapsules was still higher than 80%. GSPE encapsulated in SA-MC and SA-HPMC microcapsules results in lesser degradation and can be absorbed more effectively. This method has potential for the delivery of colon-specific materials while exhibiting a sustained-release characteristic.     

Effects of methyl cellulose-based coating on physiochemical properties and chemical hazards of Chinese fried dough cake during storage

Coating has been used as a practical method to ensure the physiochemical properties and reduce the chemical hazard of fried foods. Methyl cellulose (MC) was used as a coating material to pretreat Chinese fried dough cake (CFDC) before frying. The results showed that the water content, hardness and L* value of the 1% MC coated sample were 31.67%, 848.54 g and 51.62, respectively, at the seventh day at 25 °C. Coating contents 1% MC could reduce the oil content, hardness, and extent of browning and improve the physiochemical properties of CFDC on 7 days of storage. Coating contents 1% MC also reduced the acid value, peroxide value, p-anisidine value, malondialdehyde content, 4-hydroxy-2-(E)-hexenal content, 4-hydroxy-2-(E)-nonenal content, acrylamide content and glycidyl ester content in CFDC on 7 days of storage. Our work contributes to the control of the oil content and chemical hazards for fried food during storage by applying an edible coating.     

Stabilizing effect of the cyclodextrins additive to spray-dried particles of curcumin/polyvinylpyrrolidone on the supersaturated state of curcumin

Although curcumin is considered to have various therapeutic effects, its use as a functional food or supplement is restricted owing to its low water solubility and bioavailability. To increase the solubility of curcumin in water, the use of polyvinylpyrrolidone (PVP) and vinylpyrrolidone-vinyl acetate copolymers with a pyrrolidone skeleton was noted to be promising. In particular, the bi-component formulations of curcumin/PVP prepared through spray drying exhibited an amorphous state in powder X-ray diffraction observations and temporally increased the apparent solubility of curcumin to over 5000 times that of untreated curcumin; nevertheless, after 24 h, the solubility decreased owing to the unstable supersaturated state of curcumin. The addition of α-cyclodextrin (α-CyD) in the bi-component curcumin/PVP formulation helped maintain the supersaturated state of curcumin, whereas the addition of β- and γ-CyD led to the collapse of the supersaturated state. The addition of α-CyD can likely help inhibit the nucleation and crystal growth of curcumin, through the interaction among the solubilized units of curcumin/PVP and α-CyD.     

Facile construction of cellulose/layered double hydroxides nanocomposite membranes with high strength and antibacterial properties

High-strength regenerated cellulose/ZnAl-layered double hydroxides (LDH) composite membranes (RCL) with good mechanical and antibacterial performance were developed by stirring vigorously cellulose and LDH in NaOH/urea aqueous solvent system at −12°C. The obtained cellulose/LDH composited materials were characterized and the results indicated that well dispersion of LDH in the cellulose matrix. The tensile strength of RCL membranes were enhanced to 92.1 MPa from 68.3 MPa for that of RC film because of the strong interfacial interaction between the LDHs and cellulose matrix as well as the high rigidity of the LDHs. The addition of LDH into the cellulose could improve the thermal stability, water resistance, and flame retardant of the regenerated cellulose film. Zn²⁺ ions were exited in the cellulose/ZnAl-LDH materials, leading to good antibacterial activities against Staphylococcus aureus and Escherichia coli, which is important for RCL composite materials in antibacterial packaging filed.     

Fabrication of bacterial cellulose with high efficient loading of Ag and TiO2 nanoparticles for removing organic dyes

As a new advanced oxidation technology, photocatalytic technology has broad application prospects in the field of wastewater treatment. However, in the actual use process, there will be difficulties in catalyst recovery and reuse. This article successfully prepared bacterial cellulose (BC) loaded silver and titanium dioxide nanoparticles (Ag-plated TiO₂/BC composite pellicle) by in situ embedding method. BC not only works as the carrier to load TiO₂ and Ag NPs but also adsorbs dyes to promote the reaction. As a reusable photocatalytic film, it is convenient to use and recycle in terms of testing and characterization compared with powders. The results show that Ag and TiO₂ nanoparticles were closely embedded in BC. We evaluated the photocatalytic degradation performance of the catalyst on methylene blue (MB), active red X-3B, and Rhodamine B. When the reaction time was 2 h, the dye removal rates were 71%, 68%, and 82.6%. At the same time, through the inhibition zone experiment, it was found that the material has a certain inhibitory effect on both Escherichia coli and Staphylococcus aureus. Therefore, the supported catalyst prepared by this method has the advantages of high catalytic activity, relatively stable property, easy recovery, and tailorability, making it potentially applicable in sewage post-treatment links.