广盐性硅藻披针舟形藻在高盐和低盐胁迫下的抗氧化响应

有关藻类耐盐的抗氧化响应机制的研究报道很少,披针舟形藻(Navicula lanceolata)是从盐场分离到的广盐性硅藻,文章研究了其在长期高盐及低盐胁迫下的抗氧化响应.与对照组(1.6% NaCl)相比,在低盐(0%,0.5%,0.8%,1.0%NaCl)及高盐(3.2%,4.8%,6.4%,8.0%,9.6%NaCl)胁迫条件下,披针舟形藻的生长受到抑制,胞内膜氧化产物丙二醛的含量显著升高,表明藻细胞内出现了氧化损伤.在高盐及低盐胁迫下,胞内的抗氧化酶超氧化物歧化酶、抗坏血酸过氧化物酶、过氧化氢酶和谷胱甘肽还原酶的活性均增强,非酶抗氧化剂抗坏血酸和还原型谷胱甘肽含量均增加.上述研究结果显示,披针舟形藻通过提高抗氧化酶的活性及非酶抗氧化剂的含量来应对长期盐胁迫下的氧化损伤,细胞抗氧化系统的响应是藻耐受长期盐胁迫的机制之一.     

miR-642a-3p对藻蓝色素抑制非小细胞肺癌活性的调控作用

藻蓝色素(PC)是一种来自海洋藻类的天然色素蛋白复合体，也是一类重要的食品功能因子，具有抗肿瘤、抗炎、增强免疫等生理活性，被广泛应用于功能性食品、医药及化妆品等领域。藻蓝色素对非小细胞肺癌(NSCLC)细胞活性的抑制作用已被证实，然而其机制尚不明确。本研究以miR-642a-3p为切入点，探究藻蓝色素抑制NSCLC细胞活性的机制。试验结果表明，藻蓝色素能够上调4种NSCLC细胞(A549、H1299、H460和LTEP-a2)中miR-642a-3p的表达水平。过表达干预细胞中的miR-642a-3p水平能够显著抑制4种细胞的体外增殖、迁移和非锚定生长能力。此外，转染miRNA抑制剂干预miR-642a-3p的表达，在一定程度上增强了细胞的活性。本研究初步揭示miR-642a-3p上调表达参与藻蓝色素抑制NSCLC细胞活性的过程，为藻蓝色素的深入研究和利用提高科学依据。     

神秘果素的研究进展

神秘果素(miraculin,MIR)是在神秘果中(Synsepalum dulcificum)发现的一种变味糖蛋白,又称为变味魔术师。神秘果素由191个氨基酸组成,其主要活性形式为二聚体和四聚体,His-30和His-60是这个糖蛋白的活性中心位点,Asn-42和Asn-186是神秘果素的糖基化位点,Cys对蛋白的结构和折叠也有一定的影响。神秘果素本身并没有甜味,在中性条件下不表现出活性,但是在酸性条件下能够产生让酸的食物变甜的活性,并且这种影响能够持续一段时间(1～ 2 h);另一方面,神秘果素能够在一定程度上提高糖尿病动物对胰岛素的敏感性。最新的制备方法是通过从神秘果中直接提取、转基因到植物中和在微生物中进行表达等方法。综述了神秘果素的结构、功能和制备方法等方面的研究进展。     

食用蓝色素及其使用现状研究进展

我国允许添加在食品中的蓝色素有栀子蓝色素、藻蓝蛋白及靛蓝。栀子蓝色素是由茜草科植物栀子的果实制得的。藻蓝蛋白色素多从螺旋藻、蓝藻、念珠藻等藻类植物中提取加工而成。植物靛蓝是用蓼蓝、菘蓝、木蓝、马蓝等含有吲哚酸成分的植物叶子发酵制成。花青素也是食品中常见的色素,某些花青素在一定条件下可作为食品中的蓝色着色剂使用。作为食品中的蓝色着色剂,研究最多的为紫甘蓝色素。紫甘蓝色素是从十字花科红球甘蓝及紫球甘蓝等的叶子中提取分离得到的天然色素。本文对我国食用蓝色素的种类、来源进行了概括总结;对食用蓝色素的生成过程进行详细阐述;本文还对食用蓝色素的使用现状进行了简要概括,以期为今后我国蓝色素生产提供理论依据。     

我国食用天然蓝色素研究进展

天然色素具有安全、营养、多功能性的特点.天然蓝色素是天然色素中的稀缺色素.植物和微生物是生产天然蓝色素的主要原料来源.植物天然蓝色素主要有靛蓝、栀子蓝、藻蓝蛋白色素等.链霉菌、假单胞菌、假交替单胞菌、杜檊氏菌、黄杆菌、出芽短梗霉、光合细菌、基因工程菌株等微生物中的某些种类能够产生天然蓝色素,其中放线菌紫(红)素、绿脓菌素、紫色杆菌素为兼具抗生素作用的蓝色素.超声波破碎、柱层析和高速逆流色谱、超临界流体法、微滤和超滤等先进技术应用于天然蓝色素的提取分离及精制纯化,微胶囊化、酯化、醚化、酰化等促进色素稳定的反应技术也被应用于改善天然蓝色素的稳定性及色素的其它性能.     

富硒牡蛎肽的制备及其抗氧化和血管紧张素转化酶抑制活性研究

为开发兼具抗氧化和血管紧张素转化酶(angiotensin converting enzyme, ACE)抑制活性的富硒牡蛎肽，该研究以富硒牡蛎蛋白为原料优化制备富硒牡蛎肽，并对其硒含量、氨基酸组成、抗氧化活性和ACE抑制活性进行评价。结果表明，富硒牡蛎肽的最佳酶解条件为时间4 h、温度37℃、酶底比0.5%、pH 1.0、底物质量浓度7 g/100mL。该条件下制备的富硒牡蛎肽富含与抗氧化和ACE抑制活性相关的疏水性氨基酸和酸性氨基酸，其清除DPPH自由基和ABTS阳离子自由基的EC₅₀值分别为1.365、1.074 mg/mL,并呈现出良好的细胞抗氧化活性(EC50:1.114μg/mL),对HepG2细胞的氧化损伤具有显著的保护作用，且呈量效关系。此外，富硒牡蛎肽的ACE抑制活性较强，这可能与其良好的抗氧化活性具有内在关联性。富硒牡蛎肽具有良好的抗氧化和降血压活性，该研究结果为牡蛎源富硒肽研究奠定了前期基础，为天然富硒营养健康食品的开发提供了理论依据。     

螺旋藻藻蓝色素分离纯化及亚基结构分析

为得到高纯度藻蓝色素，采用盐析、透析、羟基磷灰石(Hydroxyapatite HA)柱层析、SDSPAGE等方法对螺旋藻中的藻蓝色素进行了分离纯化及分子质量测定，还对藻蓝色素α亚基和β亚基的结构进行了模拟。经17.5%硫酸铵一步盐析得到藻蓝色素纯度为2.45,50%硫酸铵二步盐析将纯度提高至2.70，再经HA层析得到成品，纯度为4.37；纯化后的样品经SDS-PAGE得到清晰的2条带，分别为α亚基和β亚基，分子质量为17.2 ku和19.7 ku；用SWISS-MODEL和Py MOL对藻蓝色素亚基的结构进行模拟。实验结果可为藻蓝色素的进一步开发利用提供参考。     

提高乳酸菌细菌素合成量方法的研究进展

细菌素是某些细菌通过核糖体合成机制产生的蛋白质或多肽,能够抑制与其亲源关系相同或相近的微生物,某些细菌素在食品加工和发酵过程中能抑制致病菌和腐败菌。乳酸菌被认为是一般公认安全,其细菌素具有安全性高、稳定性好、抑菌谱广等优点,作为一种新型食品防腐剂备受关注,但商品化的乳酸菌细菌素十分有限,仅限于Nisin和Pediocin PA-1等少数几种,合成量低是细菌素在食品中应用受限的主要原因之一。从不同原料中筛选高产菌株、发酵培养基和发酵条件优化、诱变育种、原生质体融合、基因工程方法、群体感应系统调控六个方面,论述了增加乳酸菌细菌素合成量的方法,以期为实现乳酸菌细菌素的工业化生产提供一定的借鉴。     

三种硅藻产多不饱和脂肪酸分析

采用f/2培养基,对3种硅藻:牟氏角毛藻(Chaetoceros mualleri)、三角褐指藻(Phaeoda-ctytuum tricornutum)、硅藻舟形藻(Navicala incerta)进行培养及脂肪酸组成研究。牟氏角毛藻和三角褐指藻的生长周期短,生物量较高。3种硅藻的脂肪酸组成相近,主要的脂肪酸是C14:0,C16:0,C16:1(n-7)和C20:5(n-3),多不饱和脂肪酸中C20:5(n-3)(EPA)含量最高,其中三角褐指藻中的EPA含量达到11.7%。3种硅藻的DHAC22:6(n-3)含量都较低。通过调整三角褐指藻和牟氏角毛藻的培养条件,可以提高EPA含量,作为优良的水产饵料。     

藻蓝色素蛋白诱导非小细胞肺癌H1299细胞凋亡的机制

藻蓝色素蛋白是一种被广泛认可的天然食品着色剂,也是一种重要的功能性食品,具有优良的抗炎、抗氧化及抗肿瘤特性。前期试验表明：藻蓝蛋白能够诱导非小细胞肺癌H1299细胞的凋亡。本研究以高通量转录组技术为手段,对藻蓝蛋白处理前、后的H1299细胞进行差异基因的筛选,探究藻蓝蛋白在非小细胞肺癌中的调控机制。转录组分析显示：藻蓝蛋白能够显著降低H1299细胞内toll-白介素1受体域接头蛋白（TIRAP）基因的表达;采用siRNA干预TIRAP的表达后,H1299细胞出现凋亡,细胞形态发生非正常改变,细胞增殖能力显著降低,促凋亡蛋白Bax表达上调,抑凋亡蛋白Bcl-xL表达下调;同时,沉默TIRAP的表达能够显著降低H1299细胞中NF-κB信号通路的活性。本研究表明：藻蓝蛋白能够抑制TIRAP的表达,通过降低NF-κB信号通路的活性而诱导H1299细胞的凋亡。此结果揭示了藻蓝蛋白在非小细胞肺癌中的作用机制,为肺癌的潜在治疗和藻蓝类功能性食品添加剂的开发和利用提供一定的理论依据。     

Marine Pseudoalteromonas sp. Composes Most of the Bacterial Population Developed in Oysters (Tiostrea chilensis) Spoiled During Storage

ABSTRACT: To identify bacteria associated with spoilage in oysters, changes in both the load and composition of the bacterial community occurring in storage were followed. Oyster spoilage was accompanied by a 100-fold increase in the number of CFU. Molecular analysis revealed that a large proportion of the bacteria present in spoiled oysters possessed an intergenic 16S-23S rDNA spacer of approximately 400 bp. A spacer with the same size was also found in spoiled oysters of different origin and dates of harvest. The bacterial strains containing this spacer may constitute a common cause of the oyster spoilage. These strains were salt-dependent marine Pseudoalteromonas species and were probably present in oysters before harvest.     

Cryptosporidium and Giardia in commercial and non-commercial oysters (Crassostrea gigas) and water from the Oosterschelde, The Netherlands

The intestinal parasites Cryptosporidium and Giardia cause gastro-enteritis in humans and can be transmitted via contaminated water. Oysters are filter feeders that have been demonstrated to accumulate pathogens such as Salmonella, Vibrio, norovirus and Cryptosporidium from contaminated water and cause foodborne infections. Oysters are economically important shellfish that are generally consumed raw. Commercial and non-commercial oysters (Crassostrea gigas) and oyster culture water from the Oosterschelde, The Netherlands, were examined for the presence of Cryptosporidium oocysts and Giardia cysts. Nine of 133 (6.7%) oysters from two non-commercial harvesting sites contained Cryptosporidium, Giardia or both. Six of 46 (13.0%) commercial oysters harboured Cryptosporidium or Giardia in their intestines. Data on the viability of (oo)cysts recovered from Oosterschelde oysters were not obtained, however viable (oo)cysts were detected in surface waters that enter the Oosterschelde oyster harvesting areas. The detection of Cryptosporidium and Giardia in oysters destined for human consumption has implications for public health only when human pathogenic (oo)cysts that have preserved infectivity during their stay in a marine environment are present. Our data suggest that consumption of raw oysters from the Oosterschelde may occasionally lead to cases of gastro-intestinal illness.     

Managing the risk of Vibrio parahaemolyticus infections associated with oyster consumption: A review

Vibrio parahaemolyticus is a Gram‐negative bacterium that is naturally present in the marine environment. Oysters, which are water filter feeders, may accumulate this pathogen in their soft tissues, thus increasing the risk of V. parahaemolyticus infection among people who consume oysters. In this review, factors affecting V. parahaemolyticus accumulation in oysters, the route of the pathogen from primary production to consumption, and the potential effects of climate change were discussed. In addition, intervention strategies for reducing accumulation of V. parahaemolyticus in oysters were presented. A literature review revealed the following information relevant to the present study: (a) managing the safety of oysters (for human consumption) from primary production to consumption remains a challenge, (b) there are multiple factors that influence the concentration of V. parahaemolyticus in oysters from primary production to consumption, (c) climate change could possibly affect the safety of oysters, both directly and indirectly, placing public health at risk, (d) many intervention strategies have been developed to control and/or reduce the concentration of V. parahaemolyticus in oysters to acceptable levels, but most of them are mainly focused on the downstream steps of the oyster supply chain, and (c) although available regulation and/or guidelines governing the safety of oyster consumption are mostly available in developed countries, limited food safety information is available in developing countries. The information provided in this review may serve as an early warning for managing the future effects of climate change on the safety of oyster consumption.     

Conditions for a 5-log reduction of Vibrio vulnificus in oysters through high hydrostatic pressure treatment

Vibrio vulnificus is frequently associated with oysters, and since oysters are typically consumed raw on a half shell, they can pose a threat to public health due to ingestion of this pathogenic marine microorganism. Oysters should be processed to reduce the number of this pathogen. High pressure processing is gaining more and more acceptance among oyster processors due to its ability to shuck oysters while keeping the fresh-like characteristics of oysters. Nine strains of V. vulnificus were tested for their sensitivities to high pressure. The most pressure-resistant strain of V. vulnificus, MLT 403, was selected and used in the subsequent experiments to represent a worst case scenario for evaluation of the processing parameters for inactivation of V. vulnificus in oysters. To evaluate the effect of temperature on pressure inactivation of V. vulnificus, oyster meats were inoculated with V. vulnificus MLT 403 and incubated at room temperature for 24 h. Oyster meats were then blended and treated at 150 MPa for 4 min, and 200 MPa for 1 min. Pressure treatments were carried out at -2, 1, 5, 10, 20, 30, 40, and 45 degrees C. Cold temperatures (<20 degrees C) and slightly elevated temperatures (>30 degrees C) substantially increased pressure inactivation of V. vulnificus. For example, a 4-min treatment of 150 MPa at -2 and 40 degrees C reduced the counts of V. vulnificus by 4.7 and 2.8 log, respectively, while at 20 degrees C the same treatment only reduced counts by 0.5 log. Temperatures of -2 and 1 degrees C were used to determine the effect of pressure level, temperature, and treatment time on the inactivation of V. vulnificus infected to live oysters through feeding. To achieve a >5-log reduction in the counts of V. vulnificus in a relatively short treatment time (or=250 MPa at -2 or 1 degrees C.     

High pressure processing of shellfish: A review of microbiological and other quality aspects

Many commercially important shellfish are filter feeders and, as a consequence, concentrate microbes from the surrounding waters. Shellfish may be relayed or depurated to reduce the level of microbial contamination, but the efficiency of these purification practices, particularly in relation to viruses and indigenous marine bacteria, is questionable. Therefore additional processing is necessary to ensure the safety of shellfish for human consumption. In recent years high pressure (HP) processing has been investigated as an alternative method for food preservation. HP technology allows inactivation of microorganisms while maintaining sensory and nutritional properties of foods. Currently, HP processing has several commercial food applications, including oysters. As well as enhancing safety and extending shelf-life, HP treatment has the additional advantage of shucking or opening shellfish, making this technology particularly beneficial to the shellfish processing industry and consumers alike.Industrial relevanceHigh pressure (HP) processing is increasingly being used in the commercial processing of oysters, due to its minimal effects on sensory and nutritional quality, the opening or shucking of oysters during treatment, and the reduction of levels of Vibrio vulnificus, a pathogen of concern particularly in the US. However, little is known of the efficacy of HP treatment in reducing other pathogens in shellfish such as human enteric viruses, which are the predominant cause of shellfish-borne disease. This article reviews the inactivation of microorganisms of importance to shellfish, particularly viruses, the commercial HP processing of oysters and the advantages of HP technology as they pertain to the seafood industry.     

Prevalence and characterization of Salmonella serovars isolated from oysters served raw in restaurants

To determine if Salmonella-contaminated oysters are reaching consumer tables, a survey of raw oysters served in eight Tucson restaurants was performed from October 2007 to September 2008. Salmonella spp. were isolated during 7 of the 8 months surveyed and were present in 1.2% of 2,281 oysters tested. This observed prevalence is lower than that seen in a previous study in which U.S. market oysters were purchased from producers at bays where oysters are harvested. To test whether the process of refrigerating oysters in restaurants for several days reduces Salmonella levels, oysters were artificially infected with Salmonella and kept at 4°C for up to 13 days. Direct plate counts of oyster homogenate showed that Salmonella levels within oysters did not decrease during refrigeration. Six different serovars of Salmonella enterica were found in the restaurant oysters, indicating multiple incidences of Salmonella contamination of U.S. oyster stocks. Of the 28 contaminated oysters, 12 (43%) contained a strain of S. enterica serovar Newport that matched by pulsed-field gel electrophoresis a serovar Newport strain seen predominantly in the study of bay oysters performed in 2002. The repeated occurrence of this strain in oyster surveys is concerning, since the strain was resistant to seven antimicrobials tested and thus presents a possible health risk to consumers of raw oysters.     

Effect of intertidal exposure on Vibrio parahaemolyticus levels in Pacific Northwest oysters

Interest in Vibrio parahaemolyticus (Vp) increased in the United States following Vp-associated gastroenteritis outbreaks in 1997 and 1998 involving the West Coast and other areas. The present study evaluated multiple aspects of Vp ecology in the Pacific Northwest with three objectives: (i) to determine the effect of low-tide exposure on Vp levels in oysters, (ii) to determine the relationship between total and pathogenic Vp, and (iii) to examine sediments and aquatic fauna as reservoirs for pathogenic Vp. Samples were collected from intertidal reefs along Hood Canal, Wash., in August 2001. Fecal matter from marine mammals and aquatic birds as well as intestinal contents from bottom-dwelling fish were tested. Total and pathogenic Vp levels in all the samples were enumerated with colony hybridization procedures using DNA probes that targeted the thermolabile direct hemolysin (tlh) and thermostable direct hemolysin (tdh) genes, respectively. The mean Vp densities in oysters were four to eight times greater at maximum exposure than at the corresponding first exposure. While tdh-positive Vp counts were generally < or = 10 CFU/g at first exposure, counts as high as 160 CFU/g were found at maximum exposure. Vp concentrations in sediments were not significantly different from those in oysters at maximum exposure. Pathogenic (tdh positive) Vp was detected in 9 of 42 (21%) oyster samples at maximum exposure, in 5 of 19 (26%) sediment samples, but in 0 of 9 excreta samples. These results demonstrate that summer conditions permit the multiplication of Vp in oysters exposed by a receding tide.     

Identification and origin of the character‐impact compounds of raw oyster Crassostrea gigas

The French consume large amounts of raw oysters. The study of the aroma of oyster Crassostrea gigas is of economic interest because it is a good method of checking the sensory quality. Aromas were extracted by vacuum steam distillation at 20 °C using whole oyster flesh. This extract presented similar sensory characteristics to raw oyster. The odour‐active compounds were characterised by gas chromatography coupled with olfactometry using a panel of 10 judges trained in seafood aroma recognition. Fifty‐nine volatile compounds were identified in oyster aroma extract. Among these, 25 were responsible for the overall odour of raw oyster. Four compounds identified in oysters were characterised by fresh and marine odour: 3‐(E)‐hexen‐1‐ol, decanal, 2‐undecanone and 3,6‐(E,Z)‐nonadien‐1‐ol. Some compounds were identified for the first time in oysters: 4‐(Z)‐heptenal (white boiled fish odour), which comes from n‐3 polyunsaturated fatty acid oxidation, and 3‐octanol (moss and sulphury odour), 2‐nonanol (cucumber odour) and octanoic acid, which arise from n‐6 polyunsaturated fatty acid oxidation. © 2002 Society of Chemical Industry     

Passage of a coccidial parasite (Eimeria acervulina) through the Eastern oyster (Crassostrea virginica)

Human illness resulting from the consumption of raw oysters is well documented for bacterial and viral pathogens but not for coccidial parasites. This study explores the passage of coccidial parasites through and the viability of these parasites in the Eastern oyster, Crassostrea virginica. Because both Cryptosporidium and Toxoplasma are human parasites and are not safe to handle, we chose to work with a close relative, Eimeria acervulina, as a surrogate. This parasite was analyzed in chickens. Oysters were found to concentrate coccidial oocysts within 6 h of exposure in a seawater tank. After 24 h, oysters still contained viable oocysts, but by 48 h, few oysters contained viable oocysts. No oysters were found to harbor oocysts 72 or 96 h after exposure to oocysts. After oysters had been exposed to oocysts for 24 h in one saltwater tank and then transferred to a clean saltwater tank for 48 h, their feces tested positive for viable oocysts. We conclude that coccidial parasites are not pathogenic to oysters, but move through oysters in just 1 day. Unless contaminated waters continuously carry oocysts, raw oysters are unlikely to pose a threat to human health through the carriage of coccidial parasites.     

Geographical,temporal, and species variation of the polyether toxins,azaspiracids, in shellfish

Azaspiracid Poisoning (AZP) is a new toxic syndrome that has caused human intoxications throughout Europe following the consumption of mussels (Mytilus edulis), harvested in Ireland. Shellfish intoxication is a consequence of toxin-bearing microalgae in the shellfish food chain, and these studies demonstrated a wide geographic distribution of toxic mussels along the entire western coastal region of Ireland. The first identification of azaspiracids in other bivalve mollusks including oysters (Crassostrea gigas), scallops (Pecten maximus), clams (Tapes phillipinarium), and cockles (Cardium edule) is reported. Importantly, oysters were the only shellfish that accumulated azaspiracids at levels that were comparable with mussels. The highest levels of total azaspiracids (microg/g) recorded to-date were mussels (4.2), oysters (2.45), scallops (0.40), cockles (0.20), and clams (0.61). An examination of the temporal variation of azaspiracid contamination of mussels in a major shellfish production area revealed that, although maximum toxin levels were recorded during the late summer period, significant intoxications were observed at periods when marine dinoflagellate populations were low. Although human intoxications have so far only been associated with mussel consumption, the discovery of significant azaspiracid accumulation in other bivalve mollusks could pose a threat to human health.