贻贝蛋白的酶解及其酶解物的抗氧化活性研究

比较了6种不同的蛋白酶(胰蛋白酶、风味蛋白酶、中性蛋白酶、木瓜蛋白酶、复合蛋白酶、碱性蛋白酶)对贻贝粗蛋白的酶解效果,确定碱性蛋白酶为最适用酶。用此酶制备不同水解度(DH 6%、DH 11.5%、DH16%、DH 20%、DH 25%)的贻贝蛋白酶解物,考察不同DH酶解产物的抗氧化活性。试验结果表明:贻贝酶解产物具有较强的抗氧化活性,并呈一定的量效关系;当DH为25%时,贻贝酶解物对DPPH自由基、超氧自由基、羟基自由基的清除率最高,分别为77.4%、75.2%、43.4%,同时具有最强的金属螯合率(64.7%);而DH为16%时,酶解物对亚油酸的过氧化抑制作用较还原型谷胱甘肽强,达65.6%。DH对酶解产物的抗氧化活性有一定的影响,但在不同的抗氧化体系中,影响趋势不一致。     

贻贝高压水射流清洗喷嘴流场仿真

目的:解决贻贝传统清洗方式存在的耗水量大、清洗效果差的问题。方法:通过Solidworks软件建立不同结构参数的轴向扇形喷嘴几何模型,分别在Fluent软件中设置参数后,对射流内外流场的速度和含水率进行数值计算。结果:喷嘴的喷射角越大,射流外流场流速的衰减速度越快,含水率越低;喷嘴的等效直径越大,射流外流场流速的衰减速度越慢,含水率越高;射流靶距过大或过小,均会影响外射流在XY平面的流速均匀性。结论:喷射角为65°,等效直径为2 mm的轴向扇形喷嘴,在射流压力为11 MPa、靶距为90 mm时,更适合贻贝外壳的射流清洗。     

Marine mussel adhesion: biochemistry,mechanisms, and biomimetics

Common blue mussel (Mytilus edulis) is a sessile organism that has unique ability to attach to a wide array of organic and inorganic marine surfaces using its holdfast structures. Strong adhesion to surfaces is essential for mussel survival, movement, and self-defense. Mussel proteins from byssal thread are structural components connecting soft mussel tissues to marine surfaces via an adhesive plaque in the distal end, while adhesive proteins from byssal plaque are responsible for mussel adhesion. Adhesive proteins are small molecules containing a high proportion of post-translationally modified amino acids such as 3,4-dihydroxyphenylalanine (DOPA). High DOPA content, small molecular size, protein flexibility, the presence of metal ions, and a high oxidation state enable strong mussel adhesion to surfaces. Mussel adhesion mechanisms depend on the composition and interactions of mussel proteins, as well as their interactions with the environment. Difficulties in the extraction of mussel adhesion proteins hamper mechanism studies and their practical applications. Development of recombinant mussel proteins and biomimetics will advance our understanding of adhesion mechanisms. In this paper, recent advances in the characterization of mussel adhesive proteins (MAPs), mussel adhesion mechanisms, application of MAPs, and the development of biomimetic biopolymers are reviewed.     

贻贝煮汁酶解液美拉德反应条件优化及其产物氨基酸组成分析

为提高对贻贝副产物的利用,以木瓜蛋白酶水解贻贝煮汁得到的酶解液为原料,经联合脱腥后进行美拉德反应,以感官评价及褐变程度为指标,研究影响贻贝煮汁酶解液美拉德反应呈味效果的各因素,并通过单因素试验及响应面试验设计优化工艺条件,以获得氨基酸态氮含量高且色泽风味好的产物。结果表明：响应面优化的美拉德反应最佳工艺条件为还原糖添加量3.3%、氨基酸添加量3.1%、加热时间55 min、初始pH 8.0,经高效液相色谱测定,贻贝煮汁液和美拉德反应产物中均检测出17 种氨基酸,在最优条件下的美拉德反应产物中,总氨基酸及必需氨基酸含量与煮汁液相比,分别增加了315.91%和428.84%。可见,经美拉德反应后的产物在营养和风味上均优于贻贝煮汁液,是研制新型贻贝调味品的理想原料。     

The Contribution of DOPA to Substrate-Peptide Adhesion and Internal Cohesion of Mussel-Inspired Synthetic Peptide Films

Mussels use a variety of 3, 4-dihydroxyphenyl-l-alanine (DOPA) rich proteins specifically tailored to adhering to wet surfaces. Synthetic polypeptide analogues of adhesive mussel foot proteins (specifically mfp-3) are used to study the role of DOPA in adhesion. The mussel-inspired peptide is a random copolymer of DOPA and N(5) -(2-hydroxyethyl)-l-glutamine synthesized with DOPA concentrations of 0-27 mol% and molecular weights of 5.9-7.1 kDa. Thin films (3-5 nm thick) of the mussel-inspired peptide are used in the surface forces apparatus (SFA) to measure the force-distance profiles and adhesion and cohesion energies of the films in an acetate buffer. The adhesion energies of the mussel-inspired peptide films to mica and TiO(2) surfaces increase with DOPA concentration. The adhesion energy to mica is 0.09 μJ m(-2) mol(DOPA) (-1) and does not depend on contact time or load. The adhesion energy to TiO(2) is 0.29 μJ m(-2) mol(DOPA) (-1) for short contact times and increases to 0.51 μJ m(-2) mol(DOPA) (-1) for contact times >60 min in a way suggestive of a phase transition within the film. Oxidation of DOPA to the quinone form, either by addition of periodate or by increasing the pH, increases the thickness and reduces the cohesion of the films. Adding thiol containing polymers between the oxidized films recovers some of the cohesion strength. Comparison of the mussel-inspired peptide films to previous studies on mfp-3 thin films show that the strong adhesion and cohesion in mfp-3 films can be attributed to DOPA groups favorably oriented within or at the interface of these films.     

贻贝食品的研究进展

贻贝是我国沿海地区常见的一种贝类,由于其风味鲜美、营养丰富而倍受人们的喜爱。本文介绍了贻贝的种类、分布、营养价值、保健功能的研究进展和贻贝产品开发的现状,并对贻贝食品开发前景进行了展望。     

Microwave‐Assisted Reversible Coordination‐Mediated Polymerization for Self‐Healing Hybrid Materials: RGO@PDA Simultaneous as Catalyst and Nanocomposites in One‐Pot

In this article, polydopamine (PDA) is efficiently adhered on the surface of graphene oxide (GO) by mussel‐inspired chemistry. The obtained reduced GO/PDA (RGO@PDA) nanocomposites are used for catalyzing reversible coordination‐mediated polymerization under microwave radiation. Well‐defined and iodine‐terminated polyacrylonitrile‐co‐poly(n‐butyl acrylate) (PAN‐co‐PnBA) is successfully fabricated by using RGO@PDA nanocomposites as catalysts. Importantly, green and novel strategy of PAN‐co‐PnBA‐type self‐healing nanocomposite materials is further fabricated with RGO@PDA as additive after polymerization as catalyst in one‐pot. As a reinforcement agent, RGO@PDA can also improve the mechanical and self‐healing properties of hybrid materials, which opens up a novel and green methodology for the preparation of self‐healing hybrid materials.     

Mussel‐Inspired Membrane Adsorber with Thiol Ligand for Patulin Removal: Adsorption and Regeneration Behaviors

Mussel‐inspired membrane adsorber with thiol ligand (SH‐membrane adsorber) is prepared by polydopamine‐assisted poly(ethylene imine) grafting and subsequent thiolation modification for efficient removal of patulin. The effects of temperature, contact time, pH, and initial patulin concentration on the adsorption capacity of the membrane adsorber are investigated. The results show that the SH‐membrane adsorber is effective to remove patulin. The adsorption capacity of the membrane can reach 1245.11 µg g^?1 for patulin. In static adsorption tests, the adsorption kinetic and equilibrium data are well fitted by the pseudo‐second‐order kinetic model and Freundlich isotherm model, respectively, meaning that the adsorption process is a multilayer chemical adsorption. The SH‐membrane adsorber can be recovered by l ‐cysteine, and the removal efficiency of patulin is maintained at about 89.23% after eight reuse cycles, compared to the 17.33% of control membrane. These results demonstrate that the SH‐membrane adsorber has a potential application for patulin removal.     

海藻糖和褐藻胶寡糖对冻藏紫贻贝品质的影响

为探讨海藻糖和褐藻胶寡糖的低温保护活性,以紫贻贝为对象,评价了海藻糖和褐藻胶寡糖处理对冻藏紫贻贝肉品质特性的影响。结果发现,在6周冻藏过程中,相比于蒸馏水和空白组,海藻糖和褐藻胶寡糖显著(p0.05)降低了紫贻贝肉解冻损失率,褐藻胶寡糖组解冻损失率低至14.28%,并维持了较好的弹性和咀嚼性等特性,同时有效抑制了紫贻贝肉中菌落总数的快速增加。此外,两种糖类浸泡处理维持了较好的肌原纤维蛋白Ca~(2+)-ATPase活力,肌原纤维蛋白Ca~(2+)-ATPase活力在0.019～0.021U/mgprot范围内,三个处理组之间并无显著性差异(p0.05)。微观观察发现,海藻糖和褐藻胶寡糖处理紫贻贝,组织结构相对较为完整、致密,细胞间隙冰晶颗粒面积较小,其组织结构保护作用明显优于焦磷酸钠处理效果。海藻糖和褐藻胶寡糖可作为一种高效的低温保护剂,用于保持紫贻贝及其制品品质及延长冻藏产品货架期。     

Vulnerability of Dreissena polymorpha Larvae to Predation by Great Lakes Calanoid Copepods: the Importance of the Bivalve Shell

Dreissena polymorpha larvae were vulnerable to predation by three different species of calanoid copepods, Diaptomus sicilis, Limnocalanus macrurus, and Epischura lacustris, when presented to these copepods in bottle experiments. The degree of vulnerability was dependent upon the stage of the larva and the type of predator: trochophore larvae (without shells) were much more vulnerable than D-stage larvae (with shells). D. sicilis and L. macrurus were offered algae as alternate food, and each cleared trochophore larvae at a higher rate than algae. However, the clearance rate for D. sicilis feeding on D-stage larvae was not significantly different from zero, suggesting that this suspension-feeding omnivore-herbivore was not able to ingest D-stage larvae. Of the three species, the large cruising predator, L. macrurus, had the highest clearance rate for trochophore larvae (55.8 mL • animal⁻¹ • d⁻¹), but had a significantly lower clearance rate for D-stage larvae, only one eighth of that for trochophores. The smaller predator, E. lacustris, was more adept than L. macrurus or D. sicilis at preying on D-stage larvae: its clearance rate for D-stage larvae (17.9 mL • animal-1 • d⁻¹) was about one half of its clearance rate for trochophore larvae. Since bivalve larvae, including Dreissena, and copepods co-occur in many aquatic environments, our results suggest that copepod predation may have been a selective force for production of a protective shell early in the larval development of bivalves.