Extraction and Characterization of Litopenaeus vannamei’s Shell as Potential Sources of Chitosan Biopolymers

Chitin is the second most abundant polysaccharide,produced mainly as an industrial waste stream during crustacean processing.Chitin can be derived into chitosan through the deacetylation process.Conversion of shrimp waste into chitosan via the deacetylation process could be considered a practical approach for shell waste remediation.In this study,chitosan’s physicochemical characteristics extracted from two types of Pacific white leg shrimp,L.vannamei’s shell(i.e.,rough and smooth),were compared with commercial chitosan.The yield,moisture,ash,solubility,water and fat binding capacity were measured.The degree of deacetylation(DDA)was calculated using FTIR,and their chemical Structure was confirmed using XRD and SEM-EDS.Both extracted chitosan showed no significant difference in yield,moisture,ash,solubility and water binding capacity but showed a significant difference with commercial chitosan.Moreover,the fat binding capacity of commercial chitosan showed the lowest percentage(408.34±0.83%)as compared to extracted chitosan(smooth shell 549.59±12.48%;rough shell 500.55±12.10%).The DDA indicated that extracted chitosan from the smooth and rough shell was considered good chitosan as compared to commercial chitosan with 84.08±1.27%,80.78±0.79%and 74.99±1.48%,respectively.Additionally,the presence of hydroxyl and amino groups from FTIR and a good crystallinity index was recorded using XRD of extracted chitosan.Based on observed characteristics,shrimp shell waste from L.vannamei can achieve chitosan standard quality as a biopolymer and highly potential to be applied in various industrial applications.

Heterosis and heritability estimates for the survival of the Pacific white shrimp(Litopenaeus vannamei) under the commercial scale ponds

The aim of the present study is to detect the potential of the base population from diallel crosses of eight introduced strains of the Pacific white shrimp（Litopenaeus vannamei） for improving the yield. Heterosis and heritability were estimated for pond survival at commercial farm conditions for the base population that included 207 full-sib families from a nested mating design by artificial insemination. Among all the hybrids,the heterosis ranged from –11.37%（UA1×UA2） to 20.53%（UA3×SIN） with an average of 0.953%. The results showed that more than half of the hybrids（51.85%） have negative heterosis for survival rate, but most of the hybrids with positive heterosis have high estimates. The high proportion of negative heterosis for survival rate reminders us that the survival trait also should be considered in the crossbreeding program to avoid yield decrease. However, high positive heterosis manifested in most of the hybrids for survival indicates the usefulness of these hybrids for improving the survival to obtain higher yield by crossbreeding in this breeding program. The heritability estimate for pond survival was 0.092±0.043 when genetic groups were included in the pedigree, and it was significantly different from zero（P〈0.05）. The results from this study also indicated that significant improvement for survival is possible through selection in L. vannamei.

EST-derived SNP discovery and selective pressure analysis in Pacific white shrimp(Litopenaeus vannamei)

Pacific white shrimp has become a major aquaculture and fishery species worldwide.Although a large scale EST resource has been publicly available since 2008,the data have not yet been widely used for SNP discovery or transcriptome-wide assessment of selective pressure.In this study,a set of 155 411 expressed sequence tags(ESTs) from the NCBI database were computationally analyzed and 17 225 single nucleotide polymorphisms(SNPs) were predicted,including 9 546 transitions,5 124 transversions and 2 481 indels.Among the 7 298 SNP substitutions located in functionally annotated contigs,58.4%(4 262) are non-synonymous SNPs capable of introducing amino acid mutations.Two hundred and fifty nonsynonymous SNPs in genes associated with economic traits have been identified as candidates for markers in selective breeding.Diversity estimates among the synonymous nucleotides were on average 3.49 times greater than those in non-synonymous,suggesting negative selection.Distribution of non-synonymous to synonymous substitutions(Ka/Ks) ratio ranges from 0 to 4.01,(average 0.42,median 0.26),suggesting that the majority of the affected genes are under purifying selection.Enrichment analysis identified multiple gene ontology categories under positive or negative selection.Categories involved in innate immune response and male gamete generation are rich in positively selected genes,which is similar to reports in Drosophila and primates.This work is the first transcriptome-wide assessment of selective pressure in a Penaeid shrimp species.The functionally annotated SNPs provide a valuable resource of potential molecular markers for selective breeding.

TAT Improves in vitro Transportation of Fortilin Through Midgut and into Hemocytes of White Shrimp Litopenaeus vannamei

Fortilin is a multifunctional protein implicated in many important cellular processes. Since injection of Pm-fortilin reduces shrimp mortality caused by white spot syndrome virus (WSSV), there is potential application of fortilin in shrimp culture. In the present study, in order to improve trans-membrane transportation efficiency, the protein transduction domain of the transactivator of transcription (TAT) peptide was fused to fortilin. The Pichia pastoris yeast expression system, which is widely accepted in animal feeds, was used for production of recombinant fusion protein. Green fluorescence protein (GFP) was selected as a reporter because of its intrinsic visible fluorescence. The fortilin, TAT and GFP fusion protein were constructed. Their trans-membrane transportation efficiency and effects on immune response of shrimp were analyzed in vitro. Results showed that TAT peptide improved in vitro uptake of fortilin into the hemocytes and midgut of Litopenaeus vannamei. The phenoloxidase (PO) activity of hemocytes incubated with GFP-Fortilin or GFP-Fortilin-TAT was significantly increased compared with that in the control without expressed fortilin. The PO activity of hemocytes incubated with 200 μg mL-1 GFP-Fortilin-TAT was significantly higher than that in the group with the same concentration of GFP-Fortilin. Hemocytes incubated with GFP-Fortilin-TAT at all concentrations showed significantly higher nitric oxide synthase (NOS) activity than those in the control or in the GFP-Fortilin treatment. The present in vitro study indicated that TAT fusion protein improved the immune effect of fortilin.

Effect of Shrimp(Litopenaeus vannamei) Farming Waste on the Growth, Digestion, Ammonium-Nitrogen Excretion of Sea Cucumber(Stichopus monotuberculatus)

In this study, specific growth rate(SGR), ingestion rate(IR), food conversion ratio(FCR), apparent digestion ratio(ADR) and ammonium-nitrogen excretion were determined for sea cucumber(Stichopus monotuberculatus) reared in plastic containers(70 L; 4 containers each diet treatment). Sea cucumbers were fed with five diets containing different amounts of farming waste from shrimp(Litopenaeus vannamei)(100%, 75%, 50%, 25% and 0) and a formulated compound(20% sea mud and 80% powdered algae). Sea cucumbers grew faster when they were fed with diet D(25% shrimp waste and 75% formulated compound) than those fed with other diets. Although IR value of sea cucumber fed with diet A(shrimp waste) was higher than those fed with other diets, both the lowest SGR and the highest FCR occurred in this diet group. The highest and the lowest ADR occurred in diet E(formulated compound) and diet A group, respectively, and the same to ammonium-nitrogen excretion. The contents of crude protein, crude lipid and total organic matter(TOM) in feces decreased in comparison with corresponding diets. In the feces from different diet treatments, the contents of crude protein and TOM increased gradually as the contents of crude protein and TOM in diets increased, while crude lipid content decreased gradually as the crude lipid content in diets increased.

Optimal content and ratio of lysine to arginine in the diet of Pacific white shrimp, Litopenaeus vannamei

The optimal quantity of dietary lysine (Lys) and arginine (Arg), and the optimal ratio of dietary Lys to Arg for Pacific white shrimp Litopenaeus vannamei were investigated. Coated Lys and Arg were added to a basal diet (37.99% crude protein and 7.28% crude lipid) to provide graded levels of Lys and Arg. The experimental diets contained three Lys levels (2.51%, 2.11%, and 1.70% of total diet), and three Arg levels (1.41%, 1.80%, and 2.21% of total diet) and all combinations of these levels were tested. Pacific white shrimp, with a mean weight of 3.62±0.1 g, were randomly distributed in 36 fiberglass tanks with 30 shrimp per tank and reared on the experimental diets for 50 days. After the feeding trial, the growth performance, survival, feed conversion rate (FCR), body composition and protease and lipase activities in the hepatopancreases of the experimental shrimps were determined. The results show that weight gain (WG), specific growth rate (SGR), FCR, body protein, body Lys and Arg content were significantly affected by dietary Lys and Arg (P<0.05) and improved when dietary Lys and Arg levels were 2.11% 2.51% and 1.80% 2.21%, respectively. Protease and lipase activities in the hepatopancreases of the shrimps appeared higher when dietary Lys and Arg quantities were 2.11% 2.51% and 1.80% 2.21%, although the difference was not statistically significant (P>0.05). Therefore, according to our results, the optimal Lys and Arg quantities in the diet of Pacific white shrimp, L. vannamei, were considered to be 2.11%-2.51% and 1.80%- 2.21%, respectively, and the optimal ratio to be 1:0.88-1:1.05.

Application of Wet Waste from Shrimp(Litopenaeus vannamei) with or Without Sea Mud to Feeding Sea Cucumber(Stichopus monotuberculatus)

In the present study, the applicability of the wet waste collected from shrimp(Litopenaeus vannamei) to the culture of sea cucumber(Stichopus monotuberculatus) was determined. The effects of dietary wet shrimp waste on the survival, specific growth rate(SGR), fecal production rate(FPR), ammonia- and nitrite-nitrogen productions of sea cucumber were studied. The total organic matter(TOM) level in the feces of sea cucumber was compared with that in corresponding feeds. Diet C(50% wet shrimp waste and 50% sea mud mash) made sea cucumber grow faster than other diets. Sea cucumber fed with either diet D(25% wet shrimp waste and 75% sea mud mash) or sole sea mud exhibited negative growth. The average lowest total FPR of sea cucumber occurred in diet A(wet shrimp waste), and there was no significant difference in total FPR between diet C and diet E(sea mud mash)(P > 0.05). The average ammonia-nitrogen production of sea cucumber in different diet treatments decreased gradually with the decrease of crude protein content in different diets. The average highest nitrite-nitrogen production occurred in diet E treatment, and there was no significant difference in nitrite-nitrogen production among diet A, diet B(75% wet shrimp waste and 25% sea mud mash) and diet C treatments(P > 0.05). In each diet treatment, the total organic matter(TOM) level in feces decreased to different extent compared with that in corresponding feeds.

Inheritance of AFLP markers and genetic linkage analysis in two full-sib families of the marine shrimp Litopenaeus vannamei(Crustacea,Decapoda)

The cultivation of the marine species of shrimp Litopenaeus vannamei has emerged as one of the segments that best develop in the Brazilian aquaculture, representing the agribusiness that grew the most in recent years. Regarding the economic importance of the farming of this species in Brazil, further studies on genetic improvement were conducted. A F2 segregating population consisting of 192 samples for each G1 and G2 families, from crossing inbred lines was used for the studies performed in the present work. The genetic linkage analysis was based on polymorphic markers derived from nine AFLP (Amplified Fragment Length Polymorphism) primers. Fourteen genetic linkage groups including 103 segregating polymorphic markers were constructed covering350 cMfor G1 and four genetic linkage groups including 59 markers were constructed covering300 cMfor G2. Simple marker analyses were performed among individuals evaluated phenotypically, finding markers linked to genes that may be potentially important and useful to assess characteristics of economic importance for traits related to weight and the disease IMN (idiopathic muscle necrosis). The statistical model including markers explained major proportion of phenotypic characteristic weight in relation to disease incidence IMN.

凡纳滨对虾(Litopenaeus vannamei)感染白斑症病毒(WSSV)后大颗粒血细胞的变化

采用抗凡纳滨对虾大颗粒细胞的单克隆抗体,应用免疫细胞化学方法,分析了凡纳滨对虾人工感染白斑症病毒(WSSV)后血细胞中大颗粒细胞的变化。研究表明,凡纳滨对虾感染WSSV后,大颗粒细胞的细胞质较正常细胞的多;从WSSV感染凡纳滨对虾的第1天至第3天,大颗粒细胞的数量增加幅度较大。同时,大颗粒细胞占血细胞总数的比例也增加较大第1天为15.2%,第2天为18%,第3天增大到45.9%,而后大颗粒细胞的比例稍有下降,到第8天下降到43.3%,但仍明显高于对照组(健康虾的大颗粒细胞比例为15.2%)。

凡纳滨对虾(Litopenaeus vannamei)不同世代养殖群体的遗传多样性分析

采用微卫星位点对凡纳滨对虾的海南群体(进口亲虾繁育的第1世代:G1)、山东和饶平群体(G2)、湛江2和湛江3群体(G3)、湛江1和上海群体(G4)共4个世代7个养殖群体的遗传多样性进行了分析。从21对微卫星引物中筛选出12对有效扩增引物,对7个群体共280个个体进行扩增,得到10个多态位点,共获得等位基因数63个。各位点的等位基因数在2—15个之间,各群体的平均等位基因数在4.70—5.80之间。平均观测(期望)杂合度在0.36—0.43(0.53—0.65)之间。杂合子偏离指数(D)为负值,表明存在杂合子缺失现象。对7个群体、10个多态位点进行Hardy-Weinberng平衡检测,共有54个偏离平衡。对7个群体间的遗传分化水平进行检测,得到近交系数FIS在9个多态位点均为正值,两两群体间的固定指数FST值在0.149—0.375之间。FST显著性检验表明,各群体之间的遗传分化极显著(P<0.01)。分子方差分析结果显示,大部分遗传变异(72.17%)来自于群体内,来自于群体间的遗传变异(27.83%)较小。凡纳滨对虾不同世代间遗传变异大,随着繁育世代的增加,遗传多样性降低。

Inactivation Kinetics of β-N-Acetyl-D-Glucosaminidase from Prawn (Penaeus vannamei) by Formaldehyde

β-N-Acetyl-D-glucosaminidase （NAGase, EC.3.2.1.52） is chitinolytic enzymes and disintegrate dimmer and trimer a composition of oligomers of N-acetyl-β-D-glucosamine （NAG） into monomer. Prawn （P. vannamei） NAGase is involved in digestion and molting processes. Some pollutants in seawater affect the enzyme activity causing loss of the biological function of the enzyme, which affects the exuviating shell and threatens the survival of the animal. The effect of formaldehyde on prawn （P. vannamei） β-N-acetyl-D-glucosaminidase activity for the hydrolysis of pNP-NAG has been studied. The results show that formaldehyde, at appropriate concentrations, can lead to reversible inactivation of the enzyme, and the IC50 is estimated to be 1.05mol· L^-1. The inactivation mechanism obtained from Lineweaver-Burk plots shows that the inactivation of the enzyme by formaldehyde belongs to the competitive type. The inactivation kinetics of the enzyme by formaldehyde has been studied using the progress-of-substrate-reaction method described by Tsou, and the rate constants have been determined. The results show that k＋0 is much larger than k-0, indicating the free enzyme molecule is fragile in the formaldehyde solution.

不同条件下凡纳滨对虾(Litopenaeusvannamei)能量代谢研究

通过设置不同温度、盐度、pH值和摄食状态的方法,研究凡纳滨对虾在不同条件下的无机磷、亚硝酸氮、硝酸氮、氨氮的释放率。结果表明,温度、体重、盐度、pH值和摄食状态对其代谢存在影响。无机磷、亚硝酸氮、硝酸氮、氨氮的释放率与体重呈负相关;在20—30℃的温度范围内,随着温度的上升,凡纳滨对虾磷、亚硝酸氮、氨氮的释放率均上升,硝酸氮的释放率在25℃时最高;在10—31的盐度范围内,随着盐度的升高,凡纳滨对虾[(5.341±0.041)g]磷的释放率升高,亚硝酸氮、硝酸氮、氨氮的释放率均降低;在7.5—9.0的pH值范围内,随着pH值的升高,凡纳滨对虾[(5.355±0.021)g]磷的释放率明显下降,亚硝酸氮的释放率上升,氨氮的释放率在pH值为8.5时达到最大值,硝酸氮的释放率在pH值为8.5时达到最小值;凡纳滨对虾[(0.344±0.063)g]摄食配合饲料,饱食状态下磷、亚硝酸氮、硝酸氮、氨氮的释放率比饥饿状态下分别提高了38.5%、131.3%、93.4%、93.3%。表明摄食时蛋白质代谢增加显著。

苏鲁-大别超高压岩石中锆石SHRIMP U-Pb定年研究——综述和最新进展

如何建立苏鲁-大别超高压岩石深俯冲-超高压-快速折返过程连续而完整的P-T-t轨迹及精细的年代谱系,是目前地学界研究的热点。而变质锆石是否记录深俯冲石英榴辉岩相进变质阶段的年代学信息和超高压峰期变质时代的准确归属,是目前苏鲁-大别超高压变质带需要深入研究的核心问题。本文在对前人同位素年代学方面所取得的成果进行系统总结的基础上。采用锆石中矿物包体激光拉曼和电子探针测试、锆石阴极发光图像成因分析以及SHRIMP U-Pb定年等综合研究手段,确定苏鲁-大别地体榴辉岩及其强退变质围岩在深俯冲-构造折返过程中主要经历了四个阶段的变质演化:深俯冲石英榴辉岩相进变质(Ⅰ)、超高压峰期变质(Ⅱ)、构造折返初期石英榴辉岩相退变质(Ⅲ)和构造折返晚期角闪岩相退变质(Ⅳ)。研究发现,扬子板块(中)新元古代巨量的陆壳物质在早三叠纪(246～244Ma)俯冲到华北板块之下约65km的深处。发生了石英榴辉岩相进变质,相应的变质温压条件为T=542～693℃,P=1.7～2.02GPa。这些高压石英榴辉岩相岩石在中-新三叠纪继续向下俯冲,在235～225Ma期间,俯冲的深度至少达到了170km的地幔深处,并发生了峰期柯石英榴辉岩相超高压变质,相应的变质温压条件为T=722～866℃,P>5.5GPa。苏鲁-大别超高压地体自石英榴辉岩相进变质阶段到超高压峰期变质阶段的俯冲速率为7.0km/Myr。这些超高压岩石在219～216Ma期间,发生了第一次构造抬升至75km的深处,并经历了石英榴辉岩相退变质作用的改造,退变质温压条件为T=730～780℃,P=1.7～2.6GPa。这些退变质岩石在212～205Ma期间,又经历了第二次抬升至25km中-下地壳深处,并叠加了角闪岩相退变质作用,该阶段变质温压条件为T=610～710℃,P=0.7～1.2GPa。苏鲁-大别超高压地体两次构造抬升的速率大致相同,为5.6km/Myr。该项成果不仅确定了苏鲁-大别榴辉岩及其强退变质岩石深俯冲过程石英榴辉岩相进变质-超高压峰期变质、构造折返过程石英榴辉岩相-角闪岩相退变质连续而完整的变质演化P-T-t轨迹及精细的年代谱系,而且对于重新建立苏鲁-大别巨量陆壳物质快速超深俯冲-快速折返的动力学模式有着重要的科学意义。

凡纳滨对虾(Litopenaeus vannamei)池塘生物膜低碳养殖技术研究

采用水体中设置生物膜净水栅对比实验的方法,在6口土池开展生物膜原位修复技术对土池半咸水养殖凡纳滨对虾的节能减排、养殖效益及机理的研究。结果表明,在135d的养殖期间,处理组水质的pH、TAN、NO2-N、无机氮和无机磷浓度分别显著低于对照组7.5%、78.8%、76.2%、53.2%和66.1%(P<0.05),DO浓度极显著高于对照组13.5%(P<0.01);弧菌数极显著低于对照组66%(P<0.01),细菌总数、硅藻相对密度、藻类生物多样性指数分别极显著高于对照组206%、173%、25.6%(P<0.01),藻类密度、蓝藻相对密度分别显著低于对照组64.7%、70%(P<0.05);生物膜上的细菌总数高达5.8×109 CFU/g,而弧菌数为零;虾养殖成活率、虾起捕规格、虾产量分别极显著高于对照组62.5%、53.9%、150%(P<0.01),饲料系数极显著低于对照组26.8%(P<0.01),处理组每公顷池塘养虾增加利润约22.1万元。池塘生物膜低碳养殖技术具有成本低、节能减排、增产增收、操作简便与易推广等优点,具有广阔的应用前景。

Effects of dietary supplementation with tropical microfungi Mucor circinelloides and Trichoderma harzianum powder on growth performance,bacterial communities,and the biomass nutritional profile of white shrimp grow-out culture(Litopenaeus vannamei)

Microfungi have been explored further as supplement constituents in shrimp culture due to their rich protein,lipid,essential amino acids,fatty acids,and various bioactive compounds.The researchers have evaluated the effects of two microfungi powders(Mucor circinelloides and Trichoderma harzianum)as feed supplements on growth performance,bacterial communities,and the biomass nutritional profile of white shrimp(Litopenaeus vannamei).The results showed that commercial/artificial feed(Feng-Li)with supplementation microfungi powder had a different effect on white shrimp growth performance than control after 62 days of the grow-out period.Supplementation with 1.5%M.circinelloides powder(M-2)could improve the growth performance of white shrimp,especially the survival rate(81.33%),final body weight(5.21 g),and shrimp biomass(211.35 g).In contrast,supplementation with 1.5%T.harzianum powder(T-2)did not improve the growth performance of white shrimp compared to control(p>0.05).Furthermore,it also affected the profile of the bacterial community in culture water as well as in shrimp intestines.Supplementation with both microfungi could reduce the total number of bacteria in culture water at the end of the experiment,where the lowest number was obtained in treatment T-2(3.9×10^(5)CFU/mL),followed by M-2(9.9×10^(5)CFU/mL)and control(4.4×10^(6)CFU/mL).In the culture water,20 isolates of culturable bacteria were found during the trial,with the dominant bacteria in M-2:Bacillus cereus,Bacillus velezensis,Gordonia polyisoprenivorans,T-2:Acinetobacter sp.,Gordonia polyisoprenivorans,Micrococcus luteus.Based on average well colour development(AWCD),the highest bacterial activity was in the M-2(0.297-0.707),followed by T-2(0.226-0.717)and control(0.094-0.694).The highest substrate group utilised in M-2 and T-2 were polymers(0.896 and 1.348)and control:amines(0.100).The highest Shannon diversity index was obtained in the M-2(2.508),followed by control(2.286)and the T-2(2.157).As many as 11 isolates of culturable bacteria were found in the shrimp intestine,with dominant bacteria in M-2:Bacillus velezensis,Micrococcus luteus,Bacillus cereus,T-2:Bacillus velezensis,Micrococcus sp.2,Demequina activiva.The highest bacterial activity was in M-2(2.259),followed by control(2.020)and T-2(0.050).The highest substrate group utilisation was in M-2:polymers(2.564),T-2:carbohydrates(0.094),and control:polymers(2.185).The highest Shannon diversity index was in the M-2(3.234),followed by control(3.230)and the T-2(0.751).In addition,1.5%M.circinelloides and T.harzianum supplementation increased white shrimp muscle protein content up to 79.21%and 80.40%,respectively,compared to control(76.73%).In conclusion,using Mucor circinelloides powder as a feed supplement can improve the growth performance of white shrimp,increase the functional/probiotic bacteria:B.cereus and B.velezensis in cultur and shrimp’s intestine,and increase the protein content in shrimp muscle tissue.However,more in-depth research is needed,especially on anti-nutritional compounds from fungi that affect shrimp growth.

Brackish Shrimp Farming in Northeastern Brazil: The Environmental and Socio-Economic Impacts and Sustainability

Despite the economic importance of farmed shrimp, a number of technical, environmental, economic and social problems have been widely reported in the international literature. This paper focuses on the environmental and socio-economic impacts of semi-intensive and intensive shrimp farming in the coastal region of Northeastern Brazil and the identification of options for sustainable production. In this Region, the total area dedicated to shrimp farming is approximately 18,500 ha, of which 5750 ha are located in Ceará State. The estuary of Jaguaribe river has the largest number of shrimp farms in the state of Ceará. Currently, the industry has 64 participating farms with a total area dedicated to shrimp farming of 2411.3 ha. In 2011, the total production was 13,110 tons of shrimp with an average yield of 6330 kg ha1.year-1 in a pond area of 2071.2 ha. This industry employs 2350 people that represent 23.2% of jobs generated in the two municipalities where the Jaguaribe river estuary is inserted. Compared with other countries, Brazil has reduced its exports due to high cost inputs for shrimp farming. However, the Brazilian shrimp industry has benefited from high domestic prices, despite the decreases in international price of shrimp. In 2011, the prices for size category ranged between U$ 4.67 - 6.04 for 80/100 (count of head-on shrimp), U$ 4.95 - 6.60 for 70/80 and U$ 5.

一株虾源假交替单胞菌(Pseudoalteromonas sp.)的分离鉴定及口服后对对虾体内弧菌的影响

为探讨对虾细菌性病原的微生物防控技术,采用牛津杯打孔法对分离自对虾育苗池的一株编号为2021041402-14的细菌(简称“02HN”)进行了抗菌测试,分析其对欧文氏弧菌(Vibrio owensii)、哈维氏弧菌(V.harveyi)、坎贝氏弧菌(V.campbellii)、溶藻弧菌(V.alginolyticus)、副溶血弧菌(V.parahaemolyticus)和美人鱼发光杆菌(Photobacterium damselae)等6株虾病原菌的抑菌效果及最低抑菌浓度,通过浸泡感染测试了菌株02HN对凡纳滨对虾(Litopenaeus vannamei)的生物毒性,采用16S rRNA、gyrB-rpoD串联基因序列比对法及生理生化方法对该菌进行了鉴定,并将该菌添加到饲料中投喂对虾,评价该菌对对虾体内弧菌数量的影响。结果表明:菌株02HN对欧文氏弧菌、哈维氏弧菌、坎贝氏弧菌、溶藻弧菌、副溶血弧菌和美人鱼发光杆菌均具有抑菌效果,其最低抑菌浓度分别为2.32×10~4、2.32×10~3、2.32×10~6、2.32×10~6、2.32×10~3、2.32×10~6 CFU/mL;采用02HN浓度为1×10~7 CFU/mL以下的菌液浸泡凡纳滨对虾,生物毒性不明显;分子鉴定显示,该菌与杀鱼假交替单胞菌(Pseudoalteromonas piscicida)及金丽假交替单胞菌(P.flavipulchra)最为接近,为一株假交替单胞菌(Pseudoalteromonas sp.);对虾摄食菌含量分别为1×10~5、1×10~7cells/g的饵料后,其存活及生长无显著性变化,但能显著降低对虾肝胰腺中的弧菌数量(P<0.05)。研究表明,菌株02HN在对虾养殖中具有开发应用潜能,本研究结果可为对虾细菌性病原的生物防控提供生物材料及技术思路。

虾类休闲食品的科研及产业概述

随着人们生活水平的提高,以虾类为代表的水产类休闲食品市场呈现出一片生机勃勃的景象,虾类休闲食品是以海水虾、淡水虾等高蛋白低脂肪虾类为原料加工制成的快速消费品,通过贮藏技术、预处理技术、蒸煮技术、干燥技术、保鲜技术、副产物利用、加工工艺等技术研究虾类营养型、功能型和健康型休闲食品,发展前景广阔。虾类休闲食品产业需要在基础性研发与科技创新、生产工艺及技术装备、市场革新及需求定向等方面寻求发展,品牌化、生活化、方便化、个性化是虾类休闲食品生存和发展的关键。

虾活性肽微胶囊复合可食膜的制备及其保鲜作用

针对南美白对虾易腐败和黑变问题,以羟丙甲基纤维素(HPMC)、虾活性肽微胶囊为成膜原料,研发具有保鲜功能的复合可食膜。采用单因素实验,以膜的机械性能、水蒸气透过率等为指标,考察羟丙甲基纤维素添加量、甘油添加量及虾活性肽微胶囊添加量对复合可食膜的成膜效果及膜性能的影响,并进一步研究虾活性肽微胶囊添加量对复合可食膜的红外光谱和自由基清除能力的影响,优化复合可食膜制备工艺;开展覆膜包装贮藏实验,以感官评分、pH、挥发性盐基氮含量、菌落总数等为指标,探究复合可食膜对南美白对虾的保鲜作用。结果表明,经单因素实验优化,复合可食膜的最佳膜材添加量为:羟丙甲基纤维素12%、甘油0.4%、微胶囊3%,此条件下,膜的综合性能佳。由膜抗氧化性能测定实验可得,当微胶囊添加量为3%及以上时,膜的抗氧化性能较好。傅里叶红外光谱显示,微胶囊添加量为3%~4%时,微胶囊与膜组分的交联作用较强。贮藏实验证实,复合可食膜可抑制虾体腐败,改善虾体感官,减缓机体pH上升、挥发性盐基氮激增和菌落总数增加等腐败现象,其贮藏期较无保护组可延长3~4 d,且总体保鲜效果优于HPMC空白膜甚至保鲜(PE)膜,展现出对南美白对虾的良好保鲜作用。

超高压结合真空低温烹饪技术制备即食虾及其品质特性

以南美白对虾为研究对象,对超高压联合真空低温烹饪冻干虾(sous-vide combined with high pressure cooked and freeze-dried shrimp,SPF)与传统热加工技术制备的高温熟制风干虾(boiled and hot air dried shrimp,BH)的品质进行研究。结果表明,与BH相比,SPF的硬度较低,颜色较饱满,感官评分较高,更受消费者喜爱。检测挥发性香味物质发现,SPF中的苯甲醛含量显著高于BH,SPF更具有海鲜风味。在脂肪酸含量上,SPF中多不饱和脂肪酸含量高于BH。同时,通过货架期动力学模型建立得到SPF氧化稳定性较高。因此,超高压联合真空低温烹饪技术制备即食虾可以更好地改善即食虾的品质和风味,实验结果为规模化生产高品质、风味独特且方便食用的即食虾提供了理论基础。