不同修饰基团的副溶血性弧菌适配体在磁性纳米颗粒表面的固定效果和反应活性研究

目的 研究副溶血性弧菌适配体的不同修饰基团对磁性纳米颗粒修饰效果和与副溶血性弧菌结合活性的影响。方法 采用一步合成法合成氨基修饰的磁性纳米颗粒,将其分别与氨基、生物素和羧基修饰的副溶血性弧菌适配体结合,通过紫外吸收间接分析适配体的固定率,并利用外加磁场分离目标物,平板涂布确定磁分离效果。结果 生物素修饰的副溶血性弧菌适配体与磁性纳米颗粒有更高的结合效率,为62.16%。在菌液浓度较低时,不同基团修饰的适配体与磁性纳米颗粒结合后对副溶血性弧菌的分离效果影响较小,但当菌液浓度为105 CFU/mL时,不同基团修饰对副溶血性弧菌分离效果差距明显,氨基修饰的适配体显示了更为优异的反应活性,分离率为69.24%,分别较生物素和羧基修饰的适配体高21.04%和16.26%。结论 氨基修饰的副溶血性弧菌适配体在磁性纳米颗粒表面固定后显示了更为优越的反应活性,为副溶血性弧菌分离和检测的相关应用研究提供参考。     

控制鱼糜制品中蔗糖含量的新策略

鱼糜制品因其健康和方便食用的特性而广受消费者喜爱。蔗糖常常作为冷冻保护剂和甜味剂添加到鱼糜及其制品中,以改善其低温抗冻特性和风味。然而,传统鱼糜制品的糖含量普遍偏高,这与当前追求健康的消费理念不符。如何在降低糖含量同时保证鱼糜制品的贮藏和感官特性是目前鱼糜工业生产面临的一个重大挑战。本文探讨了蔗糖在鱼糜加工贮藏中发挥的作用,分析了鱼糜制品减糖加工工艺存在的问题以及鱼糜蛋白低温下发生冷冻变性的机制。在此基础上,本文从3个方面综述了国内外降低鱼糜制品糖含量的最新研究进展:新型抗冻剂的应用、新型甜味剂的应用、物理加工技术的应用,并对减糖策略的发展方向进行了相关预测,以期为生产健康和低糖鱼糜制品加工提供理论依据。     

响应面法优化玉米芯中低聚木糖的酶法提取工艺

为提高玉米芯中低聚木糖的得率,试验以玉米芯为原料,研究酶法提取低聚木糖的最优工艺条件,对底物浓度、加酶量、酶解温度、酶解时间4个因素分别进行单因素试验,根据单因素试验结果设计BoxBenhnken中心组合试验,以还原糖含量为指标值,采用响应面分析法确定提取低聚木糖的最优工艺参数,并通过HPLC进行水解产物的分析。结果表明:最优工艺条件为底物浓度3%,加酶量40 m L/g(底物),50℃时酶解5 h所得的低聚木糖含量为3.86 mg/m L。水解产物经HPLC分析后发现其中含有较高的木二糖、木三糖等低聚木糖组分,低聚木糖(木二~木五)的相对含量达68.1%,说明优化后的酶法提取工艺能够较好的制备低聚木糖。     

Effect of Sorbitol Plasticizer on the Structure and Properties of Melt Processed Polyvinyl Alcohol Films

Poly (vinyl alcohol) (PVA) possesses wide applications as food packaging materials, but is difficult to melt process for its strong inter/intra hydrogen bonding. In this work, flexible PVA films with different content of sorbitol plasticizers were prepared by melt processing with the assistance of water. And the influence of sorbitol plasticizer content on the crystallinity, optical transparency, water‐retaining capability, mechanical properties, thermal stability and oxygen and water permeability were investigated. The results indicated that sorbitol dramatically improved the melt processing ability of PVA. Sorbitol could interact with PVA to form strong hydrogen bonding interactions, which would decrease the original hydrogen bonding of the matrix, resulting in the decrease of crystallinity degrees. The glass transition, melting and crystallization peak temperatures decreased with the increase of sorbitol. All the films exhibited fine optical transparency. The water retaining capability were improved with the increase of sorbitol. Especially, an increase in elongation at break and decrease in Young's modulus and tensile strength were observed indicating good plasticizing effect of sorbitol on PVA films. In addition, the PVA films prepared in this work exhibited fine barrier properties against oxygen and water, suggesting wide application potential as packaging materials.     

Changes in the phenolic contents and antioxidant activities of citrus peels from different cultivars after in vitro digestion

The aim of this study was to investigate the effects of in vitro digestion on the phenolic contents and antioxidant activities of citrus peels. Three different varieties of citrus peels (mandarin, ponkan and red tangerine) were treated with simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). The results showed that the SGF or SIF treatments of the citrus peels did not significantly increase the total phenolic content (TPC) or total flavonoid content (TFC), except for that of the TFC of ponkan peel treated with SGF. However, simulated in vitro digestion did improve the antioxidant activities measured with FRAP and ABTS methods. The effect of SGF was more positive than those of SIF for the FRAP assay, but the opposite was true for ABTS. Notably, both simulated digestion techniques decreased the DPPH free radical scavenging abilities. Simulated digestion in vitro changed the antioxidant activities of the citrus peels.     

短杆菌属产胆固醇氧化酶的发酵条件优化

短杆菌属(Brevibacterium sp.)是胆固醇氧化酶高产菌,对其进行底物诱导及发酵条件的优化,其最适培养基为蔗糖0.3%,酵母膏0.2%,蛋白胨0.3%,牛肉膏0.3%,K2HPO4 0.1%,MgSO4 0.05%,pH6.8。最适培养条件为接种量5%,24℃培养20h,通气量为50mL培养基/250mL三角瓶,200r/min。结果表明,胆固醇氧化酶的酶活力可达到2439U/L,比未优化前195U/L提高了12倍。在pH6.5和温度54℃条件下测得酶米氏常数Km值为7.1×10-5 mol/L。     

四种速生杨木制浆及漂白性能的研究

本文对四种5年生速生阔叶材的制浆及漂白性能进行了比较研究，结果表明：三倍体毛白杨的纤维较长，分布均一，具有较大的长宽比和小的壁腔比，纤维素含量较高，木素含量较低，是一种较好的造纸原料。四种原料分别进行了碱性亚纳一蒽醌法蒸煮并采用DED三段漂白，对其纸浆性能进行检测分析，结果表明：三倍体毛白杨易蒸煮、易漂白，其成浆得率和白度较高，物理强度较好。     

用废纸脱墨纸浆（DIP）生产生活用纸

该文简述了美国和芬兰利用废纸浆生产各种生活用纸的生产工艺.并对影响产品产量、质量、成本的因素进行了调研.说明废纸脱墨浆用于生产生活用纸与毛巾纸是完全可行的.     

潲水油氧化-吸附法脱色研究

基于潲水油理化特征,研究了双氧水、白土对潲水油脱色后的吸收光谱,建立了光谱法监控对潲水油进行双氧水氧化和活性白土吸附脱色的新方法。研究表明,25.0 g潲水油中加入3.0mL双氧水、再用1.25 g或2.50 g白土脱色时,脱色效率分别为88.1%和92.0%,若是将其放置1周,则脱色率分别可以提高到96.9%和98.1%。脱色处理后的潲水油无不良气味,可以作为洗涤产品中添加的皂化物的工业原料,具有可观的经济效益、环境效益和社会效益。     

基于CRISPR-Cas13的单增李斯特菌RNA快速检测方法的建立

为实现食品中单增李斯特菌污染的快速检测,本研究构建了一种基于CRISPR-Cas系统和Broccoli适配体的RNA均相检测技术。利用Cas 13与cr RNA锚定序列结合形成识别元件cr RNA-Cas13复合物,靶标RNA存在时可激活Cas 13的非特异性RNase活性,并利用点亮型RNA适配体Broccoli作为信号探针,监测cr RNA此-Cas13的活化状态。荧光值的变化与单增李斯特菌浓度存在线性关系,利用来检测单增李斯特菌。本研究所构建的检测可在30min内完成对于单增李斯特菌的的识别与检测,检出限为148CFU/m L,对细菌具有良好的检测特异性,可区分大肠杆菌、鼠伤寒沙门氏菌和蜡样芽孢杆菌。在牛奶模型中单增李斯特菌的加标回收率为95.15%～97.99%。该方法具有较好的灵敏度、特异性,可直接靶向检测致病菌RNA,无需逆转录、PCR扩增和核酸标记,简化了实验流程,对于实现食品中单增李斯特菌的现场检测及生物安全控制具有重要意义。