Structural and Rheological Characteristics of Alginate from Sargassum cristaefolium Extracted by Twin Screw Extruder

This study aimed to investigate the effects of process extrusion on the characteristics of Sargassum cristaefolium sodium alginate (SCSA) extracted using twin-screw extruder. Box-Behnken Design (BBD) from response surface methodology (RSM) was established to understand the effects of temperature, screw speed, and pH on the multiple-responses of alginate characteristics including intrinsic viscosity, yield, and molecular weight. The results revealed that temperature, screw speed, and pH significantly affected (P < .05) all responses. The optimum extraction condition was found at temperature of 58.18°C, screw speed of 77.99 rpm, and pH 10.11. At this condition, the response of residence time distribution was 7.07 ± 0.029 min, yield of 34.01 ± 0.12%, intrinsic viscosity of 460.13 ± 14.75 mL/g, and molecular weight of 217.94 ± 7.14 × 10³ g/mol. This alginate had mannuronic acid to guluronic acid (M/G) ratio of 0.28, and the L-guluronic acid block was 0.78, which was higher than the D-mannuronic acid block. Rheological characterization of SCSA in aqueous solution was shear-thinning pseudoplastic, and alginate gel in 1 M CaCl₂ was more elastic than liquid.     

珠江口海域双胞旋沟藻赤潮对卤虫幼体、鱼苗和虾苗的急性毒性

为研究2009年10月下旬在广东珠海海域爆发的双胞旋沟藻赤潮对养殖鱼类及水体中其它生物的影响,实验以卤虫幼体、金鼓鱼苗和凡纳滨对虾苗作为受试生物,在赤潮现场测试双胞旋沟藻对卤虫幼体、鱼苗和虾苗的急性毒性效应。结果显示,24 h双胞旋沟藻对卤虫幼体的LC₅₀(半致死浓度)为9.55×10⁴/mL,藻密度为2.5×10³/mL的双胞旋沟藻对卤虫幼体的LT₅₀(半致死时间)为48.5 h。60 h内该赤潮水体对鱼苗和虾苗的存活无不利影响,卤虫幼体和金鼓鱼苗均可摄食双胞旋沟藻,卤虫幼体对双胞旋沟藻的摄食率低。研究表明,双胞旋沟藻赤潮水体对卤虫幼体有一定的毒性作用,但在低藻密度条件下,卤虫幼体能以该藻为食并维持其生命,双胞旋沟藻对金鼓鱼苗和凡纳滨对虾苗无急性毒性作用。     

Protein Dispersions and Hydrolysates from Shark (Isurus oxyrinchus)

Manually-deboned muscles of shark (Isurus oxyrinchus) were ground and then washed sequentially with water, 0.5% NaCl and 0.5% NaHC0₃ solutions. Washed myofibrillar proteins were dispersed in water and then acidified. Dispersions so obtained were stable to heat treatment at 100°C followed by centrifugation at 5000 x g, as approximately 90% of proteins remained in solution. The acidified dispersions had low solubility in the pH range of 5 to 8, but were highly soluble under other pH conditions. Apparent viscosity of dispersions was dependent on temperature, pH and protein concentration. The amino acid composition and calculated protein efficiency ratio (PER) of washed proteins were similar to that of the original meat; howevcr, over 85% of free amino acids were removed upon aqueous washings of the meat. Hydrolysates obtained via an Alcalase-assisted process from the original shark muscles or washed myofibrillar proteins exhibited unique functional characteristics with respect to their water-holding capacity and emulsifying properties.     

High water-temperature tolerance in photosynthetic activity of <Emphasis Type="Italic">Zostera marina</Emphasis> seedlings from Ise Bay,Mie Prefecture,central Japan

Photosynthetic activities of seedlings of Zostera marina were successively measured using a gas volumeter for 6 days at seven light (0–400 μmol photons/m² per s) and 11 water temperature conditions (5–35°C). The seedlings were collected from mature plants (Ise Bay, central Japan), and stored and cultured in incubators accurately controlled at each test temperature. The maximum gross photosynthesis (P _maxg) was recorded at an optimal water temperature of 29°C after 0 days. After 6 days, P _maxg appeared at 25°C and most plants cultured at 29–30°C bleached and withered after the drastic increase of light compensation point (I _c). On the contrary, at 5–28°C, the photosynthetic activities either changed little (5–25°C) or recovered after a temporal reduction (26–28°C); seedlings survived and looked healthy after being cultured for 6 days. The recovery was thought to be an acclimation to tolerate higher water temperature. As a result, the critical upper water temperature for Z. marina seedlings was proposed as 28°C. The temperature was consistent with the previously reported maximum water temperature in habitats around the southern boundary of Z. marina in the northern hemisphere.     

Development,Characterization, and Antimicrobial Activity of Gelatin/Chitosan/ZnO Nanoparticle Composite Films

ABSTRACT

In order to enhance antimicrobial activity of the film, zinc oxide (ZnO) nanoparticles were incorporated in gelatin/chitosan composite film, and the physical-mechanical properties were investigated. The film-forming solution of gelatin/chitosan/ZnO films showed increased gel strength (GS), elastic modulus (G’), and viscous modulus (G’’) compared to that of the Control. Fish gelatin/chitosan/ZnO films showed lower water vapor permeability (WVP), higher glass transition temperatures (T_g), and antibacterial activities against Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Vibrio parahemolyticus. Fourier transform infrared spectra (FTIR) and microstructure studies indicated gelatin, chitosan, and ZnO interactions determined the properties of the composite film.     

Atlantic halibut (Hippoglossus hippoglossus) vitellogenin: induction,isolation and partial characterization

Vitellogenin (VTG) synthesis was induced by repeated injections of estradiol-17 in juvenile Atlantic halibut (Hippoglossus hippoglossus). VTG eluted as a large, phosphoprotein containing peak on DEAE-Sephacel chromatography of plasma from estradiol-17 treated juvenile and mature female, but not mature male halibut. A purification procedure for Atlantic halibut VTG was developed, where VTG was precipitated with MgCl₂, EDTA and distilled water, and the precipitated protein submitted to anion exchange chromatography on DEAE-Sephacel. Precipitated VTG eluted as a broad, partly dissociated peak on DEAE-Sephacel, when chromatography was run at 4°C, but the protein appeared intact when analysed both by SDS PAGE and native PAGE. DEAE-Sephacel chromatography at room temperature resulted in an irregular elution pattern and a dissociated protein fraction, as analysed by SDS PAGE. Biochemical characterization of VTG showed that the molecular mass of the monomer was ca 160 kDa, as estimated by SDS-PAGE. The total lipid content was 19.8% w/w, with 64%, or 12.7% of the total weight, as phospholipid. Protein bound phosphorus constituted 0.62% w/w of halibut VTG. Plasma dilution curves from mature and maturing female halibut were parallel with a dilution curve from halibut egg yolk homogenate in an homologous RIA. Plasma from mature male, but not juvenile halibut crossreacted with the VTG antiserum.     

Determination of 3,5,3′-triiodo-L-thyronine (T3) levels in tissues of rainbow trout (Salmo gairdneri) and the effect of low ambient pH and aluminum

Tissue T₃ (3,5,3′-triiodo-L-thyronine) concentrations were measured in rainbow trout, Salmo gairdneri, after digestion by Pronase or collagenase and extraction with ethanolic ammonia (99:1, v/v) followed by 2N NH₄OH and chloroform. Recoveries of [¹²⁵I]T₃ administered in vivo or in vitro were high and consistent and there was close parallelism between sample dilutions and the radioimmunoassay curve, but recoveries of unlabeled T₃ administered in vitro were low and variable. Alternatively, trout were brought to isotopic equilibrium by [¹²⁵I]T₃ infusion for 96 h, the extracted [¹²⁵I]T₃ determined by gel filtration and the tissue T₃ content calculated from the specific activity of plasma [¹²⁵I]T₃. By the latter method, tissue T₃ concentrations were: intestine (4.2 ng/g), kidney (2.5), liver (2.8), stomach (1.5), heart (1.0), muscle (0.7), gill (0.6) and skin (0.3). Muscle (67% of body weight) comprised the largest tissue T₃ pool (82% of all tissues examined). Seven days exposure of trout to water acidified with H₂SO₄ (pH 4.8) or acidified water containing aluminum (21.6 mM), decreased tissue T₃ content generally and particularly in muscle (14% of controls). In conclusion, skeletal muscle is the largest T₃ tissue pool and seems highly responsive to altered physiologic state.     

凡纳滨对虾养殖塘叶绿素a与水质因子的多元回归分析

2009年4-9月期间,对上海市奉贤区某凡纳滨对虾养殖场22个养殖池塘水体叶绿素a、水温、pH、溶解氧、透明度、悬浮物(SS)、总有机碳(TOC)、五日生化需氧量(BOD₅)、高锰酸盐指数(COD_Mn)等15项水质因子进行测定。取164组测定数据,进行描述性统计,分析叶绿素a与各项因子的相关性系数。分析结果显示,与叶绿素a呈极显著线性正相关的水质因子为SS、TOC、BOD₅、COD_Mn、TN、TP;呈显著正相关的为DO;而叶绿素a与透明度呈极显著线性负相关,与PO^3-₄-P呈显著线性负相关;与水温、pH、NO^-₂-N、 NO^-₃-N、NH₃-N则未呈现显著相关性。根据多元线性回归选择自变量的原则,选择了TOC、TN、PO^3-₄-P和TP₄项水质因子,建立了叶绿素a与4项水质因子的逐步回归模型:Chl.a =-0.054 5+0.0034 9 TOC+0.015 3 TN-0.418 PO^3-₄-P+0.276 TP(r=0.715 5)。利用偏回归系数检验各水质因子对叶绿素a的影响,结果表明,对叶绿素a影响从大到小依次是TP、TOC、PO^3-₄-P和TN。研究结果对进一步探讨养殖池塘生态系统的变化规律及水环境质量保护提供了依据。     

Environmental factors affecting the susceptibility of barramundi to Streptococcus iniae

A long-term environmental study was conducted to evaluate the significance of water temperature, pH and salinity on the prevalence of Streptococcus iniae mortalities in barramundi sea-cage facilities. It was determined that there is a strong association between temperature and increased mortality, specifically between 25 and 28 °C. Temperatures outside of that range result in decreased mortalities attributed to S. iniae. There was no statistical significance between pH or salinity and S. iniae induced mortality (p > 0.05), although acidic conditions (< pH 6) occurring due to anthropogenic disturbances did result in acute mortalities and S. iniae was recovered from approximately 70% these fish. Laboratory challenge studies confirmed the temperature dependence of S. iniae infections as well as the increased susceptibility of barramundi to S. iniae during acid water conditions.     

Effect of Temperature and Alkaline pH on the Physicochemical Properties of the Protein Isolates Extracted from the Whole Ungutted Lanternfish (Benthosema pterotum)

The aim of this study was to evaluate functional properties of the protein extracted from lanternfish (Benthosema pterotum). Extraction of the fish protein was performed in alkaline pHs (10 and 12) followed by precipitation at its isoelectric pH. The effects of different extraction temperatures (0, 4, 11, 25, and 30°C) were also studied. The results showed that the protein recovery yield was higher when extracted at pH 12 compared to pH 10. Furthermore, some functional properties including water holding capacity, oil holding capacity, emulsifying capacity, foaming capacity, and solubility of the protein isolated at pH 12 were higher than that isolated at pH 10 (p < 0.05). The color evaluation (L*, a*, and b*) of the samples showed protein isolated at pH 12 was lighter (higher L*) than protein isolated at pH 10, but redness (a* value) declined in both samples. Evaluation of different extraction temperatures showed that protein recovery yield and functional properties were improved with increasing temperature. Fish protein isolate can be used in the formulation of value-added products because of their distinctive functional properties.     

龙须菜苯丙烷类抑藻活性物质的分离纯化及其对6种赤潮微藻的抑藻活性

采用溶剂浸提、液液萃取、硅胶柱层析和硅胶薄层层析等分离方法以及红外光谱、质谱和核磁共振谱等光谱技术,初次从龙须菜中纯化得到4种苯丙烷类化合物:邻苯二丙酸、gossonorol、7,10-epoxy-ar-bisabol-11-ol和对羟基苯乙醇,并进一步分析了此4种苯丙烷类化合物对强壮前沟藻、赤潮异弯藻、米氏凯伦藻、球形棕囊藻、东海原甲藻和中肋骨条藻生长的影响。结果表明,它们对以上6种赤潮微藻的生长表现出明显的选择性抑制作用。其中,邻苯二丙酸、gossonorol和对羟基苯乙醇表现出更为广泛的抑藻活性。比较此4种苯丙烷类化合物和重铬酸钾对赤潮微藻生长的半抑制效应浓度EC50-96 h,发现邻苯二丙酸对强壮前沟藻、赤潮异弯藻和球形棕囊藻,gossonorol和羟基苯乙醇对赤潮异弯藻和球形棕囊藻,7,10-epoxy-ar-bisabol-11-ol对赤潮异弯藻和米氏凯伦藻在生长抑制方面比重铬酸钾更具有优势。     

三十烷醇对铜藻生长及岩藻黄素含量的影响

为探讨三十烷醇对铜藻生长的影响,本研究采用不同浓度(0、0.1、 0.5、1.0 和2.0 mg/L)的三十烷醇连续施用20 d,或用三十烷醇浸泡处理24 h后,再恢复正常条件培养20 d,分别测定了铜藻的生长、生理生化指标(光合色素、可溶性蛋白、可溶性糖)以及岩藻黄素含量的变化情况。结果显示,连续施用5 d时,各组藻体的比生长速率(RGR)、叶绿素a(Chl.a)、类胡罗卜素(Car)、可溶性蛋白、可溶性糖的含量均显著高于对照组;15 d时,2.0 mg/L浓度组的铜藻生长受到抑制,各项生理指标均显著下降;20 d时,除了0.1 mg/L浓度组的铜藻生长仍有促进外,其他3个较高浓度的施用组均受到不同程度的抑制,且三十烷醇的浓度越高,抑制作用越明显。经三十烷醇浸泡处理的藻体恢复正常条件培养5 d时,各组藻体的RGR、Chl-a、Car、可溶性蛋白和可溶性糖的含量均显著上升;10 d时,0.5和1.0 mg/L浓度组的铜藻生长速率仍显著高于对照组,但15 d时已与对照组无显著差异,且综合各项生理生化指标,1.0 mg/L组的促进作用最为明显,这种促生长的作用能持续到处理后10 d左右。岩藻黄素的含量除连续施用2.0 mg/L组在实验20 d时低于对照组外,其余各实验组在培养20 d内均显著高于对照组,其中1.0 mg/L三十烷醇浸泡处理24 h恢复培养10 d,可使岩藻黄素的含量提高79.5%。研究表明,连续施用低浓度的三十烷醇(0.1 mg/L) 20 d或以1.0 mg/L三十烷醇每10 d浸泡处理24 h,对铜藻的生长和岩藻黄素的积累有显著的促进作用。     

鲢鳙混养对三角帆蚌生长和养殖水质影响的围隔实验

2008年4月23日—9月21日通过围隔实验,研究了不同鲢鳙混养比例对三角帆蚌生长及水化学指标的影响。实验中鲢鳙混养比例设置了6个水平,分别为0/0(对照组),100/0,70/30,50/50,30/70和0/100。实验开始和结束时测量三角帆蚌湿重,壳长和壳宽。每个月上下旬测量围隔水化学指标包括NO3N、NO2N、NH3N、TN、TP、PO4P和COD。实验结果表明,鲢鳙混养比例100/0的围隔蚌壳长相对生长率显著低于混养比例0/0,50/50和0/100的围隔(P<0.05),而不同混养比例下蚌的成活率、蚌壳宽及蚌重增长均无显著差异(P>0.05)。从水质来看,混养比例30/70围隔TP显著低于100/0(P<0.05),COD显著低于100/0及70/30(P<0.05),NH3N显著低于100/0(P<0.05)以及PO4P显著低于70/30(P<0.05)。因此,综合蚌生长及水质指标,混养比例30/70围隔对三角帆蚌养殖最有利。     

江蓠琼胶的研究Ⅰ.琼胶的提取与处理

琼胶(Agar),又称琼脂、冻粉,是由某些红藻(石花菜、江蓠、伊谷草等)加水煮沸提取出的一种极有经济价值的多糖。它在80℃以上时形成溶胶,而在30—40℃时则转变成凝胶。琼胶分子主要是由D-半乳糖和3,6-内醚-L-半乳糖交替地通过C1,3和C1,4相结合成的长链;另外尚含有一定量的SO_4、Ca、糖醛酸等。琼胶由于具有特殊的物理化学性质,因而在食品工业、医药卫生以及其他科学研究方面有广泛的用途。解放前,我国的琼胶产量非常少,国内消耗大量依靠进口;解放后,琼胶工业得到了较迅速的发展。我国琼胶工业一向是用石花菜作原料,当前石花菜还是完全依靠天然生长的,产量比较有限,加之藻体生     

Annual variation of potential predation impacts on larval and juvenile marbled sole <Emphasis Type="Italic">Pseudopleuronectes yokohamae</Emphasis> by sand shrimp <Emphasis Type="Italic">Crangon uritai</Emphasis> in Hakodate Bay,Hokkaido

An investigation was conducted to evaluate the annual variation in potential predation impact (PPI) on larval and juvenile Pseudopleuronectes yokohamae by Crangon uritai in Hakodate Bay using predator-prey size relationships. Laboratory experiments were designed to estimate the favorable prey size of C. uritai through back-calculation of body length (BL) of P. yokohamae from sagittal otolith diameter observed in the stomachs of C. uritai. The most favorable prey-predator size ratio (BL of P. yokohamae-total length (TL) of C. uritai) class was 0.15–0.19, and ranged from 0.12–0.31. There was a significant positive correlation between the BL increase of P. yokohamae and the bottom water temperature in the field, such that BLs stagnated during the cold year of 1999 from April to June, and increased during the warm year of 2002. In contrast, no significant correlation was found between the TL increase of C. uritai and the bottom water temperature. Moreover, there were no significant differences in the mean TL of C. uritai between months (April–June) or years (1998–2002). Variation of PPI depended on the relationships between the growth rates of P. yokohamae and bottom water temperature. Therefore, the warm year of 2002 resulted in higher potential predation impact (PPI≥20), and it was at least 20 days shorter than that of the cold year of 1999. These results suggest that increased bottom water temperature in the nursery area was one of the most important factors for cumulative predation loss.     

Probabilities of Low Nighttime Temperatures during Stocking and Harvest Seasons for Inland Shrimp Culture

Litopenaeus vannamei is cultured in earthen ponds at southern US inland sites when water temperatures permit shrimp survival and growth. The probability of a minimum air temperature ≤14 C for one, three, or five consecutive days at one coastal and eight inland sites where L. vannamei is or could be grown in ponds is high (50%) from late March through late April at all sites except Arcadia, Florida, and Harlingen, Texas. Probabilities are 10% by early May to early June. In the autumn, the 10 and 50% probability levels are reached in early‐ to mid‐September and by late September to mid‐October, respectively. Arcadia, Florida, and Harlingen, Texas, have the longest periods with low probabilities and Pecos, Texas, has the shortest periods. The maximum pond water temperature from the previous afternoon and the minimum air temperature from that night predicted the minimum pond water temperature the following morning for Pine Bluff, Arkansas: (R² = 0.886): T_min = 1.464 + 0.169A_min + 0.727T_max, where T_min = minimum daily pond water temperature (C), A_min = minimum air temperature (C) for the same day, and T_max = maximum pond water temperature (C) from the previous day. Pond stock out and harvest decisions can be guided by minimum air temperature probabilities and predicted water temperature.     

黄芪多糖和当归多糖对维氏气单胞菌诱导鲫细胞凋亡的影响

为研究黄芪多糖(APS)和当归多糖(ASP)对维氏气单胞菌诱导鲫细胞凋亡的影响,实验设阴性对照组、阳性对照组,黄芪多糖组和当归多糖组,通过对鲫用维氏气单胞菌攻毒处理,用流式细胞仪测定血细胞的凋亡比例和细胞周期变化,并用荧光显微镜和透射电镜观察凋亡细胞的形态。结果显示,维氏气单胞菌攻毒后阳性对照组鲫血细胞的细胞凋亡率均极显著高于多糖组和阴性对照组;多糖组能显著降低鲫的细胞凋亡率且黄芪多糖组效果更显著;攻毒后鲫肝细胞和肾脏淋巴细胞出现染色质凝集、细胞核固缩边集和细胞空泡化及凋亡小体;同阴性对照组相比;维氏气单胞菌攻毒可以引起鲫血细胞周期中S/G2+M期细胞比例极显著下降,sub-G1极显著升高,抑制细胞分裂诱发凋亡;多糖组则G0/G1期细胞极显著降低,S/G2+M期细胞极显著升高,sub-G1极显著降低,促进细胞分裂抑制凋亡。黄芪多糖和当归多糖添加量在1%时能抑制维氏气单胞菌攻毒引起的细胞凋亡。     

模拟探究凡纳滨对虾磷脂在贮藏过程中的水解机理

为探究凡纳滨对虾磷脂(PL)在贮藏过程中的水解机理,本研究建立了磷脂相关酶与磷脂酰胆碱(PC)的体外模型,模拟凡纳滨对虾磷脂水解反应。实验分别从凡纳滨对虾体内分离纯化得到磷脂相关酶与PC,进行体外反应,并采用"鸟枪"脂质组学法及气相色谱—质谱法分析水解反应前后PC、溶血磷脂(LPL)及游离脂肪酸(FFA)的组成和含量变化,进而推断磷脂的水解机理。结果显示,凡纳滨对虾体内磷脂水解酶包括脂肪酶、磷脂酶A_1(PLA_1)、磷脂酶A_2(PLA_2)、磷脂酶C(PLC)及磷脂酶D(PLD),其中PLA2活力最高,可达177.87 U。体外模拟反应中,凡纳滨对虾PC含量由516.45显著降至146.14 mg/g,总FFA含量由36.42上升至568.57 mg/g,其中多不饱和脂肪酸(PUFA)显著增加了280.5 mg/g。通过相关性分析水解前后磷脂水解酶活力变化与PC含量变化,发现PC的变化与PLA2显著相关(R=0.91)。研究表明水产品中PC变化是磷脂相关酶催化的水解反应,其水解产物主要为FFA与LPC,且PLA_2对水产品贮藏过程中磷脂的水解影响最大。本实验建立了新型的体外水解模型,并初步探究了磷脂的水解机理,为水产品贮藏及磷脂酶的研究及应用奠定了理论基础。     

Hot-water solubility of mantle collagens in several cephalopod molluscs

The mantle muscles of five cephalopod species, Todarodes pacificus, Photololigo edulis, Sepioteuthis lessoniana, Sepia esculenta, and Sepia longipes, were extracted with 0.1 M NaOH to prepare crude collagen fiber, called ‘residue after alkali extraction’ (RS-AL). Solubility of the collagens in water was examined in the temperature range 20–90°C. The collagens showed a similar tendency in solubility, which gradually increased depending on the treating temperature, and the values at 40–90°C were constantly less than 47.0% for all the species examined. In addition, the collagens were estimated to denature in the approximate temperature range of 37.5–42.5°C. These results suggest that the collagens in RS-AL from these species may have relatively high resistance to hot-water extraction even after their denaturation.