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关键词： alpha-D-glucan   Glucansucrase   Branching sucrase   Dextran   Physico-chemical property  

摘要： Glycoside hydrolase family 70 (GH70) glucansucrases produce alpha-D-glucan polysaccharides (e.g. dextran), which have different linkage composition, branching degree and size distribution, and hold potential applications in food, cosmetic and medicine industry. In addition, GH70 branching sucrases add single alpha-(1 -> 2) or alpha-(1 -> 3) branches onto dextran, resulting in highly branched polysaccharides with "comb-like" structure. The physico-chemical properties of these alpha-D-glucans are highly influenced by their linkage compositions, branching degrees and sizes. Among these alpha-D-glucans, dextran is commercially applied as plasma expander and separation matrix based on extensive studies of its structure and physico-chemical properties. However, such detailed information is lacking for the other type of alpha-D-glucans. Aiming to stimulate the application of alpha-D-glucans produced by glucansucrases, we present an overview of the structures, production, physico-chemical properties and (potential) applications of these sucrose-derived alpha-D-glucan polysaccharides. We also discuss bottlenecks and future perspectives for the application of these alpha-D-glucan polysaccharides.

关键词： Electron beam irradiation   Rice grains   Starch   In vitro digestion  

摘要： In this study, rice grains were treated with electron beam irradiation (EBI). The storage properties of the irradiated rice, aswell as the physicochemical properties of isolated starches, were studied. As irradiation dose was increased from 0 kGy to 10 kGy, the lipase activity of irradiated rice decreased from 7.82 mg KOH/100 g to 5.15 mg KOH/100 g. EBI treatment did not significantly (p < 0.05) change fatty acid values. The granular structure of the isolated starches was partially destroyed after severe irradiation, and EBI treatment also caused the degradation of the molecular structures of amylopectin and amylose. All of the starches with or without EBI treatment displayed A-type crystalline structures, and 10 kGy of irradiation disrupted double-helical structures and subsequently decreased relative crystallinity. The formation of carboxyl groups reduced the digestibility of the starches, whereas the disruption of crystallites allowed digestive enzymes to access degraded starch chains easily. Overall, results demonstrated that a low dose of irradiation had insignificant effects on the quality of rice grains and corresponding starches. Thus, EBI could be a green and safe strategy for rice storage. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Yam starch   Structural properties   Physicochemical properties  

摘要： Nuoshanyao (NSY), Tiegunshanyao (TSY) and Huaishanyao (HSY) are the main cultivars of Chinese yam (Dioscorea opposita Thunb.) widely grown in China. The composition, physicochemical properties, morphology, and thermal properties of the starches from these cultivars were investigated in this study. NSY starch (17.0%) was much lower in amylose content than other cultivars (33.4-34.5%). The average particle diameter of the starches ranged from 25.83 to 28.93 mu m. Weight-average molecular weights (Mw) and number-average molecular weights (Mn) ranged from 1.29 to 1.84 x 10(5) g/mol and 5.93 to 8.36 x 10(4) g/mol, respectively. NSY starch had higher gelatinization temperature (71.5 degrees C), enthalpy (14.14 J/g), peak viscosity (8590 cP) and swelling power (12.0%) than TSY and HSY. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) tests indicated that Chinese yam starches had CB-type crystalline structure with crystallinity ranging from 21.91% to 27.08% and a short-range ordered structure. T-o, T-p, Delta H, peak viscosity and swelling power at 95 degrees Cwere significantly correlated to amylose content. The low-amylose NSY starch was found to have high gelatinization temperature, enthalpy, peak viscosity and swelling power. These specific physicochemical and structural properties indicated the industrial potential of low-amylose yam starch. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Antibacterial   Chitosan   Essential oil   Films   Nanofiber  

摘要： Plastic waste is one of the major threats to the environment, and an urgent need to replace synthetic plastics with sustainable materials is progressively growing. Herein, sustainable films based on chitosan, Satureja, and Thyme essential oils (EOs), and chitosan nanofibers (NF) were developed for the first time. To this end, 1% (w/w) of EOs and 2 wt% of NF were incorporated into the chitosan solution. Despite the very similar chemical structure of carvacrol and thymol, which are the major constituents of Satureja and Thyme EOs, respectively, they imposed notably different effects on the physicochemical properties of chitosan films. Thyme EO was more efficient at establishing hydrogen bonds with chitosan. The disruptive effect of EOs on the crystalline network of chitosan was demonstrated through X-ray diffraction analysis. Satureja and Thyme EOs decreased and increased the barrier property of the chitosan films against water vapor, respectively. However, the barrier property was greatly improved in the presence of chitosan nanofibers. Satureja EO exhibited a more efficient antibacterial property against E. coli rather than Thyme EO. The fruits and vegetables, coated by the chitosan/EO/NF system, were less perished as compared with the control and chitosan-coated samples indicating the promising potential of the developed system to be used as edible and sustainable films and coatings due to their enhanced antibacterial and barrier properties. (C) 2020 Elsevier B.V. All rights reserved.

关键词： 新工科   创新型人才   物理化学   教学改革  

摘要： 立足于"新工科"背景下创新型人才的培养目标,针对物理化学课程的现状及其存在的问题,并结合本校的人才培养定位和学生特点,以学生为中心从课程内容、教学手段、考核评价方式等方面开展教学探索和实践。教学改革不仅激发了学生的学习热情,提高了学习的主观能动性,还增强了学生的创新意识、创新能力和实践能力,有效地提升了教学效果,对"新工科"背景下具有创新精神的应用型人才的培养起了重要的推动作用。

关键词： Bioinsecticide formulation   Botanicals   Dynamic light scattering   Essential oil   Non-ionic surfactant  

摘要： Essential oils (EOs) are promising active ingredients for biopesticides, although their use under field conditions is limited by several criticisms concerning their high volatility and degradability. To overcome these negative qualities, EOs can be encapsulated inside nanostructures (i.e. nanoparticles and nano-emulsions), which can guarantee the preservation of the insecticidal properties. In the current study, oil in water (O/W) nano-emulsions of seven commercial EOs (15 % w/w of anise, artemisia, fennel, lavender, peppermint, rosemary, sage) were developed using different non-ionic surfactants and formulation processes, to identify the best possible surfactant/process to produce stable nano-formulations. The EOs were firstly examined by gas-chromatography analyses to identify their chemical constituents. Sage, rosemary, peppermint, lavender and artemisia EOs were characterized by high percentage (up to 50 % of the detected compounds) of oxygenated monoterpenes, while fennel and anise EOs were mainly constituted by phenylpropenes (e.g. anethol). Then, nano-emulsions were developed via the self-emulsifying process alone or in combination with sonication, using four surfactants with different Hydrophilic Lipophilic Balance (HLB) index (5 % w/w of Tween 20, Tween 80, Span 20 or Span 80). The physical characteristics (droplet size and surface charge) of nano-emulsions were analyzed using the dynamic light-scattering technique. Sonicated nano-formulations presented smaller and more homogeneous size of the micelles than the non-sonicated ones, resulting in more stable nano-emulsions. Furthermore, usually emulsions produced using Tween 80 as surfactant gave the best results in terms of droplet size and polydispersity index (PDI) values. Therefore, Tween 80 sonicated nano-emulsions were examined during a storage period of 28 weeks to determine their stability over time and possible alteration of their physical characteristics. Results suggest that these nano-formulations

关键词： 物理化学   线上教学   多维教学平台   翻转课堂   混合教学模式  

摘要： 新型冠状病毒肺炎(COVID-19)疫情期间,对《物理化学》课程进行了教学改革实践,构建了基于超星学习通、微信群、钉钉、雨课堂、问卷星、微信公众号的多维教学平台.将课程教学过程分成课前、课中和课后三大模块进行设计,探索基于任务导向的翻转课堂形式,以学生为中心、以教师辅导为支撑的物理化学线上教学实践.结果表明,以学生为中心、多平台结合的线上教学模式能够充分调动学生的学习热情,保证了疫情防控期间的教学质量,基本做到线上、线下课堂教学质量等效,取得了良好的教学效果,学生满意度高.获得的教学经验对线上线下混合式的教学模式也有借鉴意义.

关键词： Pullulan   Octenyl succinic anhydride   Surface properties  

摘要： Pullulan (PU) is an exo-polysaccharide used in the food and pharmaceutical industries. However, the use of PU in different industries is limited due to its highly hydrophilic nature and consequently weakness in surface properties which can be remedied by its chemical modification with octenyl succinic anhydride (OSA). For this purpose, PU modification with OSA was optimized and the results showed that the maximum degree of substitution (0.061 +/- 0.003) was obtained under pH of 9.0, pullulan concentration of 40% (w/w), temperature of similar to 40.90 degrees C, reaction time of similar to 101.21 min and OSA concentration of 14.96% (w/w). Also, the grafting of OSA on pullulan structure was confirmed by FTIR, H-1 NMR and zeta-potential analyzes. Although this modification had no significant effect on the amorphousity of pullulan, it led to an increase in viscosity and a decrease in decomposition temperature and surface tension. Improvement of emulsifying properties of PU-OSA sample was proved by the evaluation of emulsifying capacity of un- and modified samples and also, zeta-potential, particle size and viscosity of the prepared emulsions. In line with surface characteristic results, an increase in foam capacity of modified samples was observed with decreasing the interfacial tension. (C) 2020 Published by Elsevier B.V.

关键词： Origin软件   物理化学实验   燃烧热  

摘要： 利用Origin软件对实验数据进行提取及分析,可以高效精确完成实验结果处理。以萘的燃烧热测定为例,对Origin软件在实验中的应用进行详细介绍。通过深入学习,提高学生在实验课程中积极性,增强解决问题、分析问题的能力。

关键词： Luffa vine   Microstructure   Mechanical properties  

摘要： The purpose of this study is to investigate the natural Luffa vine (LV) fiber to be effectively used as cellulose fiber reinforcing material for lightweight and decay-resistance composite materials. The physical, chemical, thermal, and morphological properties of the LV fibers, together with their microstructure are investigated. The test results conclude that the LV density, microscopic characteristics, and mechanical properties show that this crop is a light-weight (200-550 kg/m(3)) natural fiber with a porous structure and a high specific modulus (1.18-2.04 MPa.m(3)/kg). The chemical, X-ray diffraction and the Fourier transforminfrared spectroscopy analyses indicate that the LV has a high lignin content (25.18%) and a relatively high relative crystallinity (37.18%) of cellulose, and it contains saponins, which increase its erosion resistance and hardness. The thermogravimetric analysis reveals that the fibers can stand up to 315.4 degrees C. Moreover, due to their kinetic activation energy of 63.9 kJ/mol, they can be used as reinforcement materials in thermoplastic green composites with a working temperature below 300 degrees. (C) 2020 Elsevier B.V. All rights reserved.