Effects of Vibrio harveyi on plasma clotting protein (coagulogen) of white shrimp Litopenaeus vannamei

Blood clotting exhibits various important functions, including the prevention of body fluid loss and invasion of pathogens in shrimp. The effects of pathogenic Vibrio harveyi on plasma of white shrimp (Litopenaeus vannamei) in vitro and in vivo were investigated in this study. The clotting protein (coagulogen) in plasma of white shrimp pre‐incubated with extracellular products (ECP) of V. harveyi was found apparently decreased and fast‐migrated in crossed immunoelectrophoresis (CIE) gels. In addition, the coagulogen had been degraded to many low molecular‐weight protein bands in plasma pre‐incubated with ECP on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) gels. When pre‐challenged with bacterial cells and ECP of V. harveyi, the white shrimp began to die at about 30 and 16 h respectively. Moreover, plasma coagulogen was decreased more obvious in shrimp challenged with ECP than that with bacterial cells as visualized in CIE gels, and total plasma protein in both group of shrimp were all decreased. Haemolymph withdrawn from moribund shrimp pre‐challenged with V. harveyi or its ECP was observed unclottable. However, the addition of clotting factors (transglutaminase and/or Ca²⁺) to these unclottable plasma could apparently promote their re‐clotting ability as jelly‐like solid observed in microtubes. The recovery of clotting ability of plasma from moribund shrimp was due to the reformation of coagulogen (200 kDa) after adding the two clotting factors as shown on CIE and SDS‐PAGE gels. The present results suggest that the infection of V. harveyi in white shrimp may not only degrade coagulogen but also influence the presence of transglutaminase and Ca²⁺ ion.     

微生物谷氨酰胺转胺酶(MTG)分批发酵模型的建立

在本文中,以本实验优化好的工艺条件,建立了关于微生物谷氨酰胺转胺酶分批发酵的数学模型方程细胞生长的动力学方程、产物合成的动力学方程和底物消耗的动力学方程。并对所建立的动力学方程进行了生物统计分析,结果表明所建立的模型具有一定的可信度。     

转谷氨酰胺酶对大豆蛋白凝胶特性及结构的影响

【目的】研究大豆种类、凝固酶种类及反应条件对大豆蛋白凝胶特性的影响。【方法】选择6种优质大豆品种吉农34、吉农28、吉农18、吉农17、吉农芽豆及北豆28,对其大豆蛋白质含量及凝胶强度进行分析;然后以未添加酶组为空白对照,分析加入转谷氨酰胺酶、碱性蛋白酶、中性蛋白酶、木瓜蛋白酶对大豆蛋白凝胶强度的影响;并通过响应面优化试验与Design-Expert8.0数据处理软件,对高强度大豆蛋白凝胶的制作工艺进行优化;通过扫描电镜和圆二光谱,对转谷氨酰胺酶作用前后大豆蛋白的凝胶构象进行表征。【结果】6种大豆中,吉农芽豆的蛋白质含量最高,凝胶特性最强。4种蛋白酶中,以转谷氨酰胺酶对大豆分离蛋白凝胶强度的提升效果最为明显。对高强度大豆蛋白凝胶制作工艺的优化结果表明,在转谷氨酰胺酶添加量为34.67U/g、反应时间2.21h、反应温度60℃、pH为7.22的条件下,大豆蛋白的凝胶强度达到最大,为181.779g·mm。通过扫描电子显微镜观察、CD图谱分析及Reed拟合计算可知,转谷氨酰胺酶作用前后大豆蛋白的表观结构、二级结构及三级结构均发生了明显变化。【结论】转谷氨酰胺酶对大豆蛋白形成凝胶具有促进作用,其通过使大豆蛋白结构发生变化来实现。     

Effect of Microbial Transglutaminase,Dietary Fiber,and Low-Salt Levels Upon Heat-Induced Meagre (Argyrosomus regius) Gels

The effects of microbial transglutaminase (MTGase; 5 g/kg, w/w) and dietary fiber (40 g pea fiber/kg product and 20 g carrageenan + 20 g konjac flour/kg product) on heat-induced meagre (Argyrosomus regius) gels with 25 and 10 g salt/kg, w/w were analyzed.

MTGase addition increased the magnitude of texture variables. Inner pea fiber had an increasing effect on gel texture. The combination of carrageenan and konjac hardened meagre gels (from 22.2 ± 1.4 to 47.3 ± 4.5 N) and enhanced water-holding capacity. Salt reduction with MTGase ensured a gelling quality similar to that of gels from Alaska pollock surimi.     

高产谷氨酰胺转胺酶茂原链霉菌的快速筛选

【目的】考察茂原链霉菌单菌落表面纹饰特征及边缘特征与产微生物谷氨酰胺转胺酶(MTG)能力的关系,建立一种根据菌落形态快速初筛高产株的方法。【方法】通过自然选育,将原始菌株分离纯化后得到不同形态的单菌落,从中选出典型的表面纹饰特征和边缘特征单菌落。用试管发酵48h后测定各形态菌落的酶活,并通过摇瓶发酵验证依据菌落形态特征初筛MTG酶高产株方法的可行性。【结果】表面厚实饱满呈馒头型且边缘毛糙的菌落酶活最高,而表面平薄、边缘光滑的菌落酶活最低。根据这一形态鉴定法,通过摇瓶发酵,筛选出了一株产MTG酶活高达6.33U/mL的菌株,其活性比原始出发株提高了20.1%。【结论】根据菌落形态筛选MTG酶高产株的方法是可行的。     

滋味物质在不同交联度鱼糜凝胶中的释放动力学分析

为探讨滋味物质在不同交联度鱼糜凝胶中的释放规律并揭示其释放机制,该研究以氯化钠、蔗糖和谷氨酸钠分别为鱼糜凝胶咸味、甜味和鲜味的代表滋味物质,通过感官评价、释放动力学模型拟合和模拟咀嚼释放等方法,分析滋味物质在不同交联度鱼糜凝胶中的释放规律。结果表明,随着交联度的增加,人体对咸味的感知逐渐降低而对鲜味的感知逐渐增强,并当交联度大于42.2%时,咀嚼破碎显著提高了鱼糜凝胶咸味和鲜味的感知（P<0.01）。氯化钠和蔗糖的释放动力学曲线符合准一级动力学模型,而谷氨酸钠的释放则符合准二级动力学模型。随着交联度的增加,鱼糜凝胶在模拟咀嚼过程中氯化钠和蔗糖的释放量先降后升,分别在交联度为42.2%和51.5%时取得最小值（4.54和3.38 mg/g）;而谷氨酸钠的咀嚼释放量则逐渐增加。相关性分析结果表明,氯化钠和蔗糖在鱼糜凝胶中的释放主要与网络结构和化学作用力相关,谷氨酸钠的释放主要与凝胶质地、凝胶持水性和化学作用力相关。综上,滋味物质在鱼糜凝胶中的释放行为受滋味物质种类、凝胶质地以及凝胶与滋味物质的相互作用等多方面的影响,且凝胶在咀嚼过程中较高的破碎程度增强了滋味物质的释放与感知。     

谷朊粉水解物对微生物谷氨酰胺转胺酶稳定性的影响

为了比较几种多肽类物质对液体微生物谷氨酰胺酶(TGase)热稳定性的影响,利用复合蛋白酶FV酶解谷朊粉,制备了不同水解程度的谷朊粉水解物(WGPHs),并对添加了WGPHs的TGase热稳定性进行了分析。结果表明,添加一定量的谷朊粉水解物能明显提高谷氨酰胺转胺酶的热稳定性,而水解植物蛋白、蛋白胨的添加对TGase的热稳定性无影响,大豆低聚肽甚至降低了TGase的热稳定性;复合蛋白酶FV水解谷朊粉过程中所产生的水解物-小麦肽具有抗氧化能力;添加水解时间为20 min的谷朊粉水解物到TGase液中,50℃处理2 h后,其酶活残存率为95.90%,较对照高30.90%,但随着水解的进行,谷朊粉水解物对提高TGase热稳定性的作用减小,甚至降低了TGase的热稳定性。由此可见,以谷朊粉水解物作为保护剂,在添加量相同的条件下,水解20 min时的谷朊粉水解物保护效果更佳。     

Pilot scale production of a non-immunogenic soluble gluten by wheat flour transamidation with applications in food processing for celiac-susceptible people

Celiac disease (CD) is an immune-mediated disease triggered by wheat gluten and related prolamins. A lifelong gluten-free (GF) diet is mandatory to normalize the intestinal mucosa. We previously found that transamidation by microbial transglutaminase of gluten was effective in suppressing the gliadin-specific inflammatory response in CD patients without influencing the main technological properties of wheat flour or semolina. In this study, we produced on a pilot scale a soluble form of transamidated gluten (soluble protein fraction, spf), characterised by a high protein content (88 mg/ml), while native gluten was dramatically reduced (32 ± 2 ppm; R5-ELISA). Using HLA-DQ8 transgenic mice as a CD model, we found suppression of interferon-γ secretion in gliadin-specific CD4⁺ T cells challenged with spf-primed dendritic cells. In terms of functional properties, spf showed both solubility and emulsifying activity values within the range of commercial soluble glutens. Notably, dough prepared by mixing rice flour with spf could leaven. After baking, blended rice bread had a higher specific volume (2.9 ± 0.1) than control rice bread (2.0 ± 0.1) and acquired wheat-like sensory features. Taken together, our results highlighted the technological value of transamidated soluble gluten to improve both nutritional and sensory parameters of GF food.     

Effects of microbial transglutaminase and starch on the thermal gelation of salted squid muscle paste

ABSTRACT:   The addition of microbial transglutaminase (MTGase) to salted squid muscle paste greatly strengthened the elasticity of the thermal gel, which was produced by the preferential cross-linking of myosin heavy chains through a two-step heating process that consisted of setting at 40°C and subsequent heating to 80°C or 90°C. Starch increased the breaking strength of thermal squid gels, but decreased the deformation. Thus, the starch-added gels became harder and less elastic. Although, when both MTGase and starch were added to squid muscle paste, the changes in viscoelastisity and myosin cross-linking reaction were similar to those with MTGase alone during setting, the storage and loss moduli of the paste sharply increased with an increase in starch content above 70°C. Subsequently, the thermal gel texture became more brittle or breakable than gels prepared by setting with MTGase only.     

水稻红莲型细胞质雄性不育幼穗发育过程中组织型转谷氨酰胺酶活性比较

以水稻红莲型细胞质雄性不育系粤泰A和保持系粤泰B的叶片和不同发育时期幼穗为材料,比较分析了水稻红莲型细胞质雄性不育幼穗发育过程中组织型转谷氨酰胺(tTG)酶活性变化,建立了适合水稻tTG酶活性分析的酶联免疫法（ELISA）测定反应体系。研究发现tTG酶活性受钙离子正调控,并且无论是粤泰A还是粤泰B,衰老叶片中tTG酶活性都高于新叶片,但粤泰A与粤泰B之间的差异不明显;不育系粤泰A自四分体到二核期的幼穗不同发育阶段,tTG酶活性随着花粉发育而增强,在二核期达到最高,而在保持系粤泰B中,tTG酶活性没有随发育进程发生显著变化。推断tTG酶与花粉败育过程中的细胞程序性死亡有关。