Genome shuffling improved acid-tolerance and succinic acid production of Actinobacillus succinogenes

Food Science and Biotechnology - Succinic acid is widely applied to chemical, pharmaceutical, food, and agricultural industries. With the rapid development of these industries, a great demand of...     

超声-转谷氨酰胺酶改善红豆蛋白功能性质及结构

采用超声联合转谷氨酰胺酶（transglutaminase,TG）处理红豆分离蛋白（red bean protein isolate,RBPI）,对其功能性质和结构特征进行分析,以探究其结构修饰与功能性质的构效关系。结果表明：超声处理5 min能够使RBPI的乳化活性和发泡能力提高,但会降低泡沫稳定性,对乳液稳定性没有显著影响,同时增加表面疏水性和游离巯基含量;TG能够提高RBPI的乳化活性、乳化稳定性及泡沫稳定性,但会降低发泡能力、表面疏水性和游离巯基含量;超声-TG联合处理的RBPI具有更高的乳化活性和泡沫稳定性,更低的表面疏水性和游离巯基含量,且酰胺Ⅰ带处吸收峰强度增加,更多的无规卷曲结构转变为有序的β-折叠结构,这可能是导致RBPI功能性质改善的原因。超声处理5 min联合TG诱导的蛋白凝胶具有更加均匀、致密的微观结构,且凝胶硬度和黏附力增加,脱水收缩作用降低;峰值温度（Tp）和热焓变（ΔH）显著增加（P＜0.05）,改善了RBPI的热稳定性或三级结构稳定性。以上结果表明RBPI经过超声处理后更利于TG对蛋白质的交联作用,超声-TG联合处理促进了蛋白质功能性质的发挥。     

超声预处理制备大豆分离蛋白/糖复合物及其结构与溶解性

将大豆分离蛋白（soybean protein isolate,SPI）分别与葡萄糖和麦芽糖进行糖基化反应,对SPI/糖复合物进行超声预处理,探讨超声预处理对SPI/糖复合物结构和溶解性的影响。葡萄糖比麦芽糖更易与SPI发生糖基化反应,超声预处理能制备高接枝度且低褐变的SPI/糖复合物,且超声预处理20 min时,SPI/糖复合物的接枝度最大。傅里叶变换红外光谱分析证明了SPI/糖复合物的形成。糖基化反应会减少热处理过程中SPI二级结构由有序向无序的转变程度,使其三级结构变得松散;超声预处理对SPI/糖复合物二级结构的影响并不显著（P＞0.05）,但会加强糖基化复合物三级结构的松散程度,这可能是导致超声预处理制备的SPI/糖复合物具有较高溶解性的主要原因。此外,溶解性的改善可能与超声预处理提高SPI/糖复合物的接枝度有关。     

玉米醇溶蛋白/聚环氧乙烷同轴静电纺丝负载姜黄素及其释放特性

玉米醇溶蛋白作为生产淀粉的副产物,大多应用在饲料方面,利用率低,本实验借助静电纺丝技术高值化利用玉米醇溶蛋白得到纳米纤维膜,并用于抗菌方面的研究。通过同轴静电纺丝技术研发具有核/壳结构负载姜黄素的玉米醇溶蛋白（Zein）纳米纤维,即将姜黄素负载在Zein和聚环氧乙烷（Polyethylene oxide,PEO）组成的三种核/壳结构纳米纤维中,并以透射电镜（TEM）、紫外分光（UV）、红外光谱（FT-IR）和XRD等进行相关表征。循环伏安（CV）的释放动力学研究表明在负载量为0.226、0.260、0.264 mg的基础上,姜黄素的封装效率达到96.02%、95.00%、90.15%,与姜黄素对Zein的亲和力略强于PEO一致;通过对姜黄素的电化学特性研究,发现玉米醇溶蛋白包聚环氧乙烷膜的缓释作用最好;借助SEM可以观察到姜黄素释放后纤维膜会出现孔洞,原有的结构遭到破坏;抗菌性研究发现,金黄色葡萄球菌比大肠杆菌的对姜黄素含量更敏感。同轴静电纺丝制得的负载姜黄素纳米纤维可用于功能性食品及生物医用产品的保鲜及贮藏保质。     

Characteristics of lipoxygenase-based and lipoxygenase-deficient soy yogurt with modified okara

Food Science and Biotechnology - Lipoxygenase-based and lipoxygenase-deficient okara were modified by Kluyveromyces marxianus fermentation, then adding modified okara back to the corresponding...     

超声预处理对大豆分离蛋白糖基化复合物酸诱导凝胶性质的影响

对溶液体系中大豆分离蛋白（soybean protein isolate,SPI）与葡萄糖和麦芽糖之间的糖基化反应进行超声预处理,探讨超声预处理对SPI/糖复合物酸诱导凝胶性质的影响。傅里叶变换红外光谱分析表明糖分子与SPI形成了共价复合物。超声预处理20 min时,SPI/糖复合物的接枝度最大。葡萄糖和麦芽糖与SPI的糖基化作用会降低蛋白质的表面疏水性（H0）和平均粒径（D43）,而超声预处理能够使SPI/糖复合物具有更高的H0和更低的D43。由于疏水相互作用的减小,糖基化反应会削弱SPI酸诱导凝胶网络,导致凝胶强度和凝胶持水性降低。然而,超声预处理能够降低或消除糖基化反应对SPI酸诱导凝胶的弱化作用,甚至能够改善蛋白质的凝胶性。     

Structural and physicochemical properties of soya bean protein isolate/maltodextrin mixture and glycosylation conjugates

The effect of mixture and conjugation with maltodextrin (MD) in aqueous solution on the structural and physicochemical properties of soya bean protein isolate (SPI) was investigated. Although the mixing of MD would not change the distribution of secondary structure and tertiary conformation of SPI, the protein aggregation was promoted through hydrophobic interaction, which resulted in the decrease in solubility and the improvement of gel strength and water holding capacity (WHC) of SPI/MD mixture. However, glycosylation decreased α-helix and increased β-structure. The bathochromic shift of the fluorescence emission maximum wavelength for SPI/MD conjugates was promoted, resulting in less compact tertiary conformation. These structural modifications might be the reason for the changes in the physicochemical properties of conjugates. After glycosylation, the surface hydrophobicity and solubility were increased, the average particle size was decreased, and the gelation properties were weakened including gel strength and WHC.     

Preparation and characterisation of curcumin-loaded pea protein-zein nanocomplexes using pH-driven method

The nanocomplexes of hydrophilic pea protein (Pp) and hydrophobic zein were prepared to encapsulate curcumin (Cur) by the pH-driven method. The properties of pea protein-zein complex were affected by many factors, of which mass ratio was one of the most important factors. The nanocomplexes with a mass ratio Pp to zein of 8:2 showed a smaller size (near 100 nm) and a higher stability than individual Pp nanoparticles. The solubility of Cur was significantly improved by the nanocomplexes prepared by this method. In neutral aqueous solution, the solubility of Cur encapsulated with the nanocomplex reached 652 μg mL⁻¹, and the nanocomplexes had excellent re-dispersibility. The main forces for the formation of nanocomplexes were hydrophobic interactions and hydrogen bonds, and the Cur existed in amorphous state in the nanocomplexes. The Cur coated with protein complexes had higher storage stability and thermal stability than Cur loaded with single protein, indicating the stronger protection on Cur provided by protein complexes. Furthermore, the nanocomplexes exhibited an improved antioxidant activity after in vitro simulated digestion. Thus, the nanocomplexes prepared by a simple and safe pH-driven method could be used for functional protection and delivery of hydrophobic bioactive compounds.     

溶剂对rac-Et[Ind]_2ZrCl_2/MMAO催化体系催化乙烯-降冰片烯共聚合的影响

采用乙基桥连二茚基二茚基二氯化锆(rac-Et[Ind]2ZrCl2)/MMAO催化体系催化乙烯/降冰片烯共聚合,比较了甲苯、苯、正己烷、环己烷及其混合溶剂作为反应介质对共聚合活性及共聚物结构的影响。通过差示扫描量热分析(DSC)对共聚产物进行了热力学性质的表征。结果表明,聚合活性和产品的玻璃化转变温度(Tg)在不同溶剂体系中有着显著的差异,在相同聚合条件下,当甲苯/苯体积比为80/20时,聚活活性达到最高,但产品的Tg和降冰片烯的插入率较低。