Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@PAM@NTA-Ni<Superscript>2+</Superscript> Magnetic Composite Nanoparticles for Highly Specific Separation of His-tagged Proteins

A facile approach has been developed to synthesize Fe₃O₄@PAM (polyacrylamide) nanoparticles (NPs) with carboxyl groups on the surfaces by copolymerization with acrylamide and acrylic acid in Fe₃O₄ NPs aqueous suspension. Nitrilotriacetic acid (NTA) was conjugated to the magnetic NPs via well-known carboniimide chemistry using EDC and NHS. The Ni²⁺ ions loaded on the surface of NPs provide abundant docking sites for immobilization of His-tagged green fluorescent proteins (His-tagged GFP). The high magnetic property of Fe₃O₄@PAM@NTA-Ni²⁺ allows an easy separation of the NPs from solution under an external magnetic field, with high His-tagged protein binding capacity (42 μg protein/mg of NPs). The NPs can be recycled for at least four times without significant loss of binding capacity to proteins. These materials show great potential to separate His-tagged protein with low-cost purification at industrial scale.     

Efficiency of acetic acid and formic acid as a catalyst in catalytical and mechanocatalytical pretreatment of barley straw

In this study, the potential of organic acids (formic acid, acetic acid) in a catalytical and mechanocatalytic conversion of lignocellulosic barley straw to valuable sugars is explored using sulfuric acid as a reference. Acid-catalyzed hydrolysis has been carried out with acid-impregnated samples as well as unmodified barley straw. In the mechanocatalytical approach, pretreatment consists of impregnation with the acid catalyst and mechanical treatment by ball milling following chemical hydrolysis. Straw samples and residues were analyzed by Fourier transform infrared spectrometry (FT-IR) whereas hydrolysate analysis was based on total reducing sugar (TRS) determination following the DNS method and capillary electrophoresis (CE) analysis. The results indicated that acetic acid and formic acid are rather mild acids yielding low TRS levels compared to the reference acid. Mechanocatalytical pretreatment slightly increased TRS yields, but not significantly. Strikingly, sulfuric acid showed an efficient conversion efficiency yielding almost 45% of TRS. Furthermore, this study provided evidence for the acetylation of straw components when acetic acid was used as catalyst. Alkali hydrolysis induced the de-esterification, but revealed no significant increase of TRS yields.     

Olfactory responses of Stegobium paniceum to different Chinese medicinal plant materials and component analysis of volatiles

Stegobium paniceum (L.) (Coleoptera: Anobiidae) is among the major pests of stored products, causing great damage to stored Chinese medicinal plant materials (CMPMs) in China. Effective control strategies are urgently needed. The aim of this study was to explore the role of volatile organic compounds in the host preference of S. paniceum. First, the olfactory behavioral responses of S. paniceum adults to volatiles from four CMPMs (Panax notoginseng, Angelica sinensis, Gastrodia elata, and Peucedanum praeruptorum) were tested in Y-tube olfactometer experiments. Then, the volatile composition of these plant materials were analyzed by gas chromatography-mass spectrometry (GC-MS). S. paniceum showed significant preferences for volatiles from the four CMPMs, compared with clean air (CA). When S. paniceum was presented with choices among different CMPMs, it showed the strongest preference for P. notoginseng, followed by A. sinensis, then G. elata, and P. praeruptorum. GC-MS analysis identified 43, 34, 28 and 60 components in the volatile profiles of P. notoginseng, A. sinensis, G. elata, and P. praeruptorum, respectively. Falcarinol (14.4%), 3-n-butyl phthalide (78.7%), p-cresol (40.1%), and β-pinene (29.1%) were the most abundant components of the volatiles of P. notoginseng, A. sinensis, G. elata, and P. praeruptorum, respectively. The olfactory responses of S. paniceum to the four CMPMs demonstrated that host-related volatiles play an important role in the host-searching process by adult beetles. This information will be useful for the development of safe and effective trapping strategies for this pest.     

Effect of ozone treatment on aflatoxin B1 and safety evaluation of ozonized corn

This paper studies the ozone treatment effect on degradation of aflatoxin B₁ (AFB₁) in corn with different moisture content (MC). The toxicity of the degradation products (DPs) of the ozone-treated AFB₁-Contaminated Corn (ACC) was also evaluated using the human hepatocellular carcinoma cell line (HepG2) as model cells. The degradation rate of AFB₁ in corn increases with ozone concentration and treatment time. The results showed that ACC with 13.47% MC was easier to be degraded by ozone than with 20.37% MC. Treated with 90 mg L⁻¹ ozone for 20 min and 40 min, AFB₁ in corn with 13.47% MC decreased from 83 μg kg⁻¹ to 18.12 μg kg⁻¹ and 9.9 μg kg⁻¹, respectively, well meeting the China National Standard of AFB₁ in corn (20 μg kg⁻¹). In order to evaluate the safety of ozone used on ACC, the impacts of AFB₁ as well as untreated and ozone-treated ACC with the same level of AFB₁ content on HepG2's survival rate, morphology, and apoptosis were studied. The results showed that ACC had high cell toxicity while the toxicity of ozone-treated ACC had no significant difference with that of the AFB₁-free culture solution. It is concluded that ozonation can quickly and effectively degrade AFB₁ in corn and diminish ACC's toxicity, and therefore, ozonation is expected to be an effective, fast, and safe method for AFB₁ degradation in ACC.     

板枣酒发酵过程中的香气变化规律及特征香气分析

目的 探究板枣酒发酵过程中的香气变化规律。方法 采用顶空固相微萃取和气相色谱-质谱联用技术(HS-SPME-GC-MS)对板枣酒发酵过程中香气成分进行分析。结果 在发酵过程中共出现了57种香气物质,醇类14种,酯类19种,酸类8种,醛酮类8种,芳香烃类8种。通过香气活性值分析,己酸乙酯,辛酸乙酯,苯乙酸乙酯,月桂酸乙酯,3-苯丙酸乙酯,正辛醛,苯乙醛,大马士酮和丁香酚为板枣发酵酒中的主要香气成分。通过主成分分析可将发酵过程分为3个阶段,发酵初始阶段,主发酵阶段,后发酵阶段。在发酵过程中萘、苯乙醛、葵酸乙酯、苯甲酸乙酯、异戊醇是对感官评分影响最大的5种香气成分。结论 本研究探究了板枣酒发酵过程的香气变化规律,为提高板枣酒产品品质提供理论依据。     

预制乌鳢鱼片的微波熟化工艺

该实验以预制乌鳢背部肌肉为研究对象,分析其在160、320、480、640和800 W的微波功率加热处理下温度分布、熟化度、感官评分、质构及水分子分布的变化,优化预制鱼片的微波熟化工艺参数。结果表明,微波功率为160、320、480、640和800 W下鱼肉在70～80℃之间鱼肉已完全熟化,通过熟化度、感官评价确定不同微波功率由低到高相应的最佳熟化时间分别在8、6、4、3和2 min,其对应最小剪切力为67.85、51.9、63.70、71.39、66.44 g。随着样品表面温度不断升高,肌肉蛋白变性,肌肉对水的束缚能力下降,自由水比例不断升高,鱼肉的剪切力整体呈先上升后下降的趋势。综合熟化度、感官评分、质构分析和水分子分布的结果,640 W处理3 min,鱼肉完全熟化,剪切力最高,其鱼肉嫩度最受欢迎,感官评分最佳,为预制乌鳢鱼片最适微波熟化参数。     

百香果皮多糖的分离纯化、结构特性及生物活性研究进展

百香果是一种生长在热带、亚热带的重要特色经济水果,多糖是构成百香果果皮的主要功能成分之一。百香果皮多糖因具有抗肿瘤、抗炎、降血脂和抗氧化等多种生物活性而备受国内外学者的高度关注。本文系统综述了国内外近十年来关于百香果皮多糖的提取、分离纯化、结构特性和生物活性的研究进展,并提出目前百香果皮多糖研究中存在的不足,以期为百香果皮多糖的研究与开发提供参考与借鉴。     

A new and direct preparation method of iron-based bimodal catalyst and its application in Fischer–Tropsch synthesis

A bimodal iron-based catalyst was prepared by a new one-step impregnation method. The active components were used as the “brick” to directly build the small pores inside the large pores of support, which was quite different from the previous bimodal catalysts that were prepared once more on a bimodal support. Comparing with the unimodal catalysts and conventional co-precipitated catalyst, the prepared bimodal catalyst exhibited excellent activity in Fischer–Tropsch synthesis due to the improved active metal dispersion and fastened diffusion efficiency. This preparation method is much simpler than the previous methods and can be extended to prepare various bimodal catalysts with different chemical compositions.     

Viscosity transition of ZnO-containing rosin

Eutectic alloy Sn–9Zn is regarded as one of the potential substitutes for Pb-containing solders, although it has some drawbacks yet to overcome. One of the problems involved is drastic viscosity increase of rosin-based flux during soldering or storage. In the present work we investigated the role of ZnO in the viscosity transition of rosin. The results show that the viscosity transition is directly caused by the presence of ZnO in molten rosin and, at a certain temperature, there exists a critical ZnO concentration for its occurrence. The critical ZnO concentration increases with temperature. A graph is presented to show the conditions for the viscosity transition, in a ZnO concentration–temperature space. The transition is found to be reversible when shifting temperature or ZnO concentration across the boundary and to assume the features of a thermally activated phase transformation.