Study on the Technologic Optimization for Hydrolysis of Silver carp By-products

The hydrolysis process for Silver carp by-products was studied. Protein hydrolysate was prepared with proteolytic enzyme, Alcalase. Hydrolysis conditions were optimized by the regression model of three factors five levels quadratic rotation perpendicular regressive design. The optimum hydrolysis conditions of hydrolyzing the protein of Silver carp by-products were determined to be concentration of enzyme (E/S) 3.33%, pH 8.54, hydrolyzing temperature 58 ℃, reaction time 90 min, concentration of substrate 8%. Nitrogen recovery was more than 75%.

Effect of filter-feeding fish silver carp on phytoplankton species and size distribution in surface water:A field study in water works

Silver carp were introduced into the pre-sedimentation pond to control excessive phytoplankton in raw water. The effectiveness of the filter-feeding silver carp on phytoplankton control and the effect of silver carp on phytoplankton community were investigated. The results showed that Microcystis could be effectively removed by silver carp stocked in the pre-sedimentation pond, and simultaneously, the concentration of single-cell phytoplankton increased obviously. The difference in phytoplankton species and single- cell phytoplankton size between in the water and in the gut of silver carp indicated that phytoplankton smaller than 5 μm, such as Chamydomonas and Platymonas, were almost not be filtered by silver carp, phytoplankton with the size between 5 and 20μm could be partly filtered, and large size phytoplankton, mainly colony-forming Microcystis could be filtered almost completely. These filter- feeding characteristics directly caused the phytoplankton size distribution biased toward miniaturization. Therefore, this biological treatment using silver carp could be applied only to deal with groups of Microcystis-dominated eutrophic water, and was not appropriate in water bodies where single-cell micro phytoplankton were dominant. Especially when silver carp are used in water treatment, a cautious attitude should be taken based on the evaluation of phytoplankton biomass and species structure features in raw water.

Screen for stage-specific expression genes between tail bud stage and heartbeat beginning stage in embryogenesis of gynogenetic silver crucian carp

A systemic study was initiated to identify stage-specific expression genes in fish embryogenesis by using suppression subtractive hybridization (SSH) technique. In this study, we presented a preliminary result on screen for stage-specific expression genes between tail bud stage (TBS) and heartbeat beginning stage (HBS) in gynogenetic silver crucian carp (Carassius auratus gibelio). Two SSH plasmid libraries specific for TBS embryos and HBS embryos were constructed, and stage-specific expression genes were screened between the two stages. 1963 TBS positive clones and 2466 HBS positive clones were sampled to PCR amplification, and 1373 TBS and 1809 HBS PCR positive clones were selected to carry out dot blots. 169TBS dot blot positive clones and 272 HBS dot blot positive clones were sequenced. Searching GenBank by using these nucleotide sequences indicated that most of the TBS dot blot positive clones could not be found homologous sequences in the database, while known genes were mainly detected from HBS dot blot positive clones. Of the 79 known genes, 20 were enzymes or kinases involved in important metabolism of embryonic development. Moreover, specific expressions of partial genes were further confirmed by virtual northern blots. This study is the first step for making a large attempt to study temporal and spatial control f gene expression in the gynogenetic fish embryogenesis.

Distribution of persistent organochlorine pesticides in tissue/organ of silver carp (Hypophthalmichthys molitrix) from Guanting Reservoir, China

The concentration of organochlorine pesticides（OCPs） in tissues and organs of silver carp（Hypophthalmichthys mofitrix） from Guanting Reservoir were investigated to evaluate the pollution potential and distribution of OCPs. A total of 16 OCPs were measured and the concentrations were in the range of 1.61-69.01 ng/g wet weight（ww） for total OCPs, 0.16- 0.75 ng/g ww for HCB. 0.75 -26.80 ng/g ww for SHCH（sum of α-,β-, γ- and δ-HCH） and 0.68-35.94 ng/g ww for SDDT（ sum of p, p＇-DDE, p, p＇-DDD, o, p＇-DDT and p, p＇- DDT）. The mean concentrations of total OCPs, HCB, ∑HCH, and ∑DDT were 18.04, 0.96, 7.14 and 9.28 ng/g ww, respectively. Among the organochlorine pesticides, β-HCH and p, p＇-DDE were the most dominant compounds in tissue and organ with the average concentrations of 4.42 and 8.14 ng/g, respectively. The results obtained in this study show that the levels of 16 OCP residues found in silver carps are low and pose no threat to human health and wildlife fed upon them on the basis of existing related quality guidelines. However, recent input of lindane and DDT might still exist in the area investigated and further investigation should be carried on.

COMPARATIVE STUDIES ON THE FEEDING CAPACITY OF SILVER CARP AND BIGHEAD CARP

Study of the feeding capacity of silver carp and bighead carp by means of experimental ecologyshowed that the filtering frequency of silver carp was slightly greater than that of bighead carp,but thatthe latter’s suction volume was much greater than the former’s so the filtering rate(filtering frequency mul-tiplied by the suction volume)of silver carp was smaller than that of bighead carp.The filtering efficien-cy of silver carp for phytoplankton was greater than that of bighead carp for them.The removal ratesof silver carp for phytoplankton were greater than those of bighead carp,but for zooplankton the formerwere smaller than the latter.For food particles about 70 μm both removal rates were almost equal.The feeding habits of the two species in natural waters is also discussed in the paper.

Influence of total dissolved gas-supersaturated water on silver carp(Hypophthalmichthys molitrix)

Dam discharges over spillways are the main reason for the gas-supersaturated water generated in rivers.Local aquatic organisms,especially fish,readily develop gas bubble disease(GBD) in a river with total dissolved gas supersaturation(TDGS).Sometimes,fish will die after a specific exposure period,which negatively affects the biological equilibrium.In this study,the influence of TDGS on silver carp was explored.Silver carp were exposed to gas-supersaturated water with TDGS levels of 140%,135%,130%,125%,120%,and 110%to test the impact of TDGS.Some silver carp died when the TDGS level was 120%or higher,and all the silver carp exposed to a TDGS level of 140%died within10 h.In comparison with the Chinese sucker,Prenant's schizothoracin,and rock carp,silver carp seem less sensitive to TDGS.In addition,we tested the catalase(CAT) activity in the muscles and gills of silver carp after they were exposed to gas-supersaturated water with a TDGS level of140%.The CAT activity changed with time;it increased first and then decreased until it was lower than the initial CAT activity.The results of this study can provide basic data for developing a standard for environmental evaluation.

Effect of Water Chestnut Powder on Gel Properties of Silver Carp Surimi

[Objectives]The effects of water chestnut powder on the gel properties and quality of silver carp surimi were investigated.[Methods]The surimi gel was prepared by adding 0%,1%,2%,3%,4%and 5%of water chestnut powder to the surimi of silver carp.The gel properties,water-holding capacity,cooking loss,whiteness value,puncture and texture profile analysis(TPA)indexes of surimi products were determined to assess the effects of adding different amounts of water chestnut powder on surimi gel.[Results]The results showed that the gel strength,breaking force and depression distance of surimi products increased first and then decreased with the increase of the addition of water chestnut powder.Compared with the control group,the hardness and chewiness of surimi gel in TPA could be significantly improved by adding water chestnut powder.When the addition of water chestnut powder was 2%,the maximum water-holding capacity was 83.68%;the cooking loss rate was the lowest;and the whiteness value was the highest.Adding 2%of water chestnut powder could significantly improve the gel properties of silver carp surimi and obtain a good gel product.[Conclusions]This study provides a scientific basis for the effective utilization of water chestnut resources and the development of new fish surimi products.

Genetic discrimination for three gynogenetic clones of silver carp Hypophthalmichthys molitrix, based on restriction endonuclease analysis of Nd5-Nd6 region of mitochondrial DNA

Three artificial gynogenetic clones of silver carp were produced for the analysis of restriction enzyme digestion patterns of ND5-ND6 region from mtDNA of the clones. It is revealed that all intraclonal individuals shared completely the same digestion patterns but among interclonal individuals did not. The three clones were mixed and cultured in a pond together for two years, and restriction endonuclease digestion patterns of ND5-ND6 were used as genetic markers to assess the growth performance of each clone.

Effect of Nitrobenzene on the Embryo Development of Bighead and Silver Carp

The effect of various concentrations of nitrobenzene on the mortality and abnormality rate of bighead and silver carp embryos were studied to provide reference for the evaluation of the effect of nitrobenzene to aquatic organisms and aquatic environment. The results showed that the development of bighead and silver carp embryos was delayed, the mortality and abnormality rates were raised when the embryos were treated with ≥0.010 mg·L^-1 nitrobenzene, and with ≥0.085 mg· L^-1 nitrobenzene, the mortality rates showed 100%

The Effect of Washing and Inhibitor on Cathepsin Activity of Silver Carp

The effect of washing and temperature on the activity of cathepsins of Silver carp was studied.The result showed that the activity of cathepsin L was higher than those of cathepsin B and H.The total catalysis activity of these three enzymes was the highest at 55℃ after washing.The inhibiting effect of soybean protein and potato starch on cathepsin L also had been studied,the results showed that soybean protein and potato starch could decrease activity of cathepsins L significantly.

AGE-0 SILVER CARP AND GIZZARD SHAD DAILY GROWTH AND HATCH TIMING IN THE MIDDLE MISSISSIPPI RIVER

The establishment of a highly efficient planktivore, Silver carp(Hypophthalmichthys molitrix), in the Mississippi River Basin has been documented as having negative impacts on native planktivore populations. Silver carp have the potential, to alter the trophic food web through negative interactions with native planktivores in large river systems. Due to increasing Silver carp ranges, interactions between Silver carp and other native planktivores is likely to increase. One abundant native planktivore that is often found in similar habitats as Silver carp is Gizzard shad(Dorosoma cepedianum). Potential competition for resources exists because of overlapping habitat use and forage. Given the similarities between these two planktivores, we sought to evaluate daily growth rates and determine hatch dates of age-0 Silver carp and Gizzard shad in the Middle Mississippi River. Silver carp and Gizzard shad were collected from the Middle Mississippi River using an electrified surface trawl from June through September with sizes ranging from 21—65 mm total length for Gizzard shad and 24—85 mm total length for Silver carp. A sample of age-0 fish(n=697) was collected at the end of the growing season including 292 Gizzard shad and 405 Silver carp. Size structure(total length in mm) of Silver carp(49.05±0.41; ± SE) was significantly greater(T= –16.43, df=695, P<0.001) than Gizzard shad(38.95 ± 0.45). Hatch dates were similar between Silver carp(July 26 th to August 18 th) and Gizzard shad(July 28 th to August 19 th). Growth of Silver carp(2.24 mm per day) was significantly greater(P<0.001,T= –11.1, df=82) than Gizzard shad(1.72 mm per day). Mortality was similar between Silver carp(28.1%)and Gizzard shad(25.1%) at this early life stage. The faster growth rates in Silver carp result in Silver carp entering the winter season larger in size with likely an increased capacity to consume plankton and decreased predation ultimately leading to higher recruitment. Knowing that there exists an overlap between Silver carp and Gizzard shad diets and habitat could alone call cause for concern. Adding that spawning occurs at a similar time and Silver carp have the ability to outgrow Gizzard shad early in life leads to major concerns about food web balance. Knowing that invasive planktivores have already shown to alter food webs in aquatic systems in North America, extra caution should be taken.

Silver Carp (<i>Hypophthalmichthys molitrix</i>, Val. 1844) Stocking in Lake Kinneret (Israel)

Silver Carp (SC) (Hypophthalmichthys molitrix, Valenciennes, 1844) is a worldwide common fish for aquaculture and stocking in lakes and reservoirs. The fish is distributed through rivers, aquaculture and stocking in about 90 countries around the world. SC was first introduced into Lake Kinneret in 1969 and continues onwards. Total number of stocked fingerlings (1969-2013) was 18.5 × 106 (average: 441 × 103 per year). The total catch (tons) of SC in Lake Kinneret was 3218 tons, average: 75 t/year. Studies on SC in East Lake, China, revealed that the fish was a phytoplanktivorous and percentage of consumed phytoplankton varied between 83% - 91% where Microcystis was the major item. In Lake Kinneret, the effects of SC and the Cichlid, Galilee St. Peters Fish (S. galilaeus) on Plankton resources are not independent and potentially competitors. SC is also known as efficient consumer of Microcystis. It was found that environmental conditions in Lake Kinneret were optimal for reasonable growth and recruitment of this fish to commercial fishery. The SC did not reproduce in Lake Kinneret and we recommended introducing annually 600 - 1000 × 103 fingerlings for the benefit of water quality protection and fishermen income.

The reports of lesions in kidney and intestine of apparently normal cultured silver carp (<i>Hypophtalmictys molitrix</i>)

Among fresh water fishes, silver carp because of fast growth rate and desired meat quality, is a dominant species in polyculture systems in Iran. This fish mainly feed on phytoplankton. In present survey kidney and intestine of 120 silver carp (Hypophtalmictys molitrix) from 4 regions in Khuzestan province-Iran have been studied. Tissue samples were provided from kidney and intestine and sectioned by routine method after paraffin embedding and finally stained with hematoxilin and eosin (H & E). The microscopic results were analyzed qualitatively and quantitatively. Microscopical analysis showed that kidney tissue had lesions including: edema, necrosis, uroliths, hemorrhage and degeneration. In different regions, fishes showed different prevalence of lesions. Edema and urolith were the most prevalent lesions (30 and 25 percent respectively). In histometric analysis the diameter of layers of intestine in some of the fish farms were significantly higher than the other regions. This increase was because of increase in muscular layer. The intensity of all lesions was estimated as light according to distribution of lesions. The probable cause of these lesions may be the high stocking density, intoxication, water quality problem such as excessive carbon dioxide. The only lesion in intestine was the excessive proliferation of mucus cells that this lesion may be created due to the improper plankton diet.

Effects of Supplemental Amount of Tuanfeng Lotus Seed Powder on Quality of Silver Carp Surimi Products

[Objectives]This study was conducted to improve the gel properties of freshwater surimi and its products. [Methods] Tuanfeng lotus seed powder was added to frozen silver carp, and the relationship between the addiamount of Tuanfeng lotus seed powder(1%, 2%, 3%, 4% and 5%) and the quality of surimi products was studied, so as to improve the quality of surimi products. [Results] The water holding capacity(86.71%±0.36%), hardness(3 566.64±51.15) g, chewiness(2 697.16±15.81) g and gel strength(692.54±23.19) of surimi products increased to the maximums when the addition amount of lotus seed powder was 3%. Meanwhile, the cooking loss rate was reduced to the minimum(13.00%±0.17%), and the sensory quality was the best, although the whiteness of surimi products decreased slightly with the increase of Tuanfeng lotus seed powder. Therefore, the quality of silver carp surimi products could be improved obviously when the dosage of Tuanfeng lotus seed powder was 3%. [Conclusions] This study provides more new ideas for improving the quality of silver carp surimi products, and simultaneously makes the development of lotus seed food more diversified.

Characterization of dominant and cellulolytic bacterial communities along the gut of silver carp Hypophthalmichthys molitrix during cyanobacterial blooms

Silver carp is one of the most important planktivorous fish in Chinese aquaculture and plays a significant role controlling cyanobacterial blooms. A balanced gut microbiota is crucial for growth and health of the host because of its important roles in immune defense, digestion of complex carbohydrates, and production of enterocytes. In our study, the dominant bacterial and cellulolytic bacterial( Clostridium I, Clostridium III, Clostridium XIVab, and Fibrobacter) communities in the contents and mucus of the silver carp gut(foregut, midgut, and hindgut) were analyzed by denaturing gradient gel electrophoresis and quantitative polymerase chain reaction(q PCR) analyses. The results revealed that the dominant and cellulolytic bacterial communities were significantly different among gut regions as well as in contents and mucus. Bacterial diversity and richness in contents and mucus increased along the gut and were higher in contents than those in local mucus. A sequence analysis of gut samples exhibited the conservative phylotypes of Proteobacteria, Actinobacteria, and Firmicutes. The gut of silver carp harbored an abundance of cellulolytic bacteria, particularly Clostridium XIV ab. The foregut segment had the highest proportions of the four cellulolytic bacteria, followed by the midgut and hindgut. However, the proportions of cellulolytic species in the silver carp gut was much lower than those in the terrestrial vertebrate gastrointestinal tract. We conclude that gut bacteria could help silver carp obtain energy from cyanobacteria, which may be why silver carp can maintain high growth rates during cyanobacterial blooms.

Fish Sauce Fermentation with Silver Carp or Offal of Surimi Processing

Fish sauce is a kind of condiments processed from fish. The L9（34） orthogonal tests have been carried out to inspect the effects of technological conditions for fermentation on the comprehensive quality of fish sauce. The conditions of the orthogonal tests are following: the fermentation temperature takes values of 35℃, 40℃ and 45℃, the percentage of Koji values of 40%, 20% and 10% and the percentage of salt values of 10%, 14% and 18%. The obtained experimental results indicate that fermentation temperature plays an important role in the improvement of sauce quality. The optimal technological conditions for sauce fermentation are of 10% salt, 45℃ and 40% koji mixed. The composition of fish sauce processed from offal of silver carp-surimi processing under the above-mentioned conditions and two commercial products have been analyzed. The results show that fish sauce processed from fish offal is nutritious and delicious. It is suggested that the fermentation of fish sauce is a potential and promising pathway to make full use of freshwater fish resources and offal in fish processing. In this study, fuzzy theory and analytic hierarchy process have been applied and the quality evaluation has been established by the combination of physico-chemical indices and sensory evaluation. The comprehensive evaluation has been taken to reflect the optimal factors for the process of sauce fermentation. The quality indexes for fish sauce contain sensory evaluation, amino nitrogen, total nitrogen, specific gravity, volatile basic nitrogen, salt concentration, brown index and acidity, represented by y1, y2, y3, y4, y5, y6, y7, y8, and y9, respectively. They form a group U= {y1, y2, y3, y4, y5, y6, y7, y8, y9,}. Using the fuzzy functions, the values of all these factors are transformed into fuzzy degrees of single factor, i.e. numerical values between 0 and 1. The fuzzy degrees of single factor in several samples are made up a matrix R. Following that, a weight of each index can be determined in the comprehensive evaluation. In the analytic hierarchy process, the weight can be obtained by the cross comparison between two different factors. The results show that the weights （W） of sensory evaluation, amino nitrogen, total nitrogen, specific gravity, volatile basic nitrogen, salt concentration, brown index and acidity are 0.356, 0.189, 0.107, 0.054, 0.097, 0.063, 0.061 and 0.073 respectively. Finally the aggregated fuzzy degree （B） of different samples is computed by B=W·R, which can be taken as the final result of comprehensive evaluation. The larger this value is, the higher the quality of sauce product would be.

两条鲢鱼小清蛋白源抗冻肽的活性及作用机制比较

目的:探讨鲢鱼小清蛋白源抗冻肽的作用机制和构效关系。方法:采用差示扫描量热和分子动力学模拟方法对比分析了两条鲢鱼小清蛋白源抗冻肽的活性、结构及其作用模式。结果:Pv-AFP 1(KAADSFNHKAFFAKVG)呈稳定的α-螺旋结构,而Pv-AFP 2(KAADSFNHKAF)倾向于呈无规卷曲;Pv-AFP 1的热滞值为0.87℃,总平均亲水性为-0.21,热滞活性和两亲性均优于Pv-AFP 2(0.74℃,-0.71);分子动力学模拟显示Pv-AFP 1能结合53个水分子,可形成16个氢键吸附至冰晶表面,结合能为-1514 kJ/mol,均大于Pv-AFP 2(能结合50个水分子,通过形成11个氢键吸附至冰面,结合能为-805 kJ/mol);尽管两条肽序列相似,但其与水分子和冰晶相互作用的主要位点和模式也有一定差异。此外,两条肽均能与冰水界面相互作用,改变了冰面的曲率从而抑制了水的结冰,但Pv-AFP 1抑制冰面生长的效果优于Pv-AFP 2,与热滞活性结果一致。结论:鲢鱼小清蛋白源抗冻肽的活性可能与构象、两亲性及其与水分子和冰晶相互作用的亲和力、位点和模式有关。

鲢滤食不同藻类的磷吸收及排泄过程研究

为探究滤食性鱼类对水体营养元素地球化学循环过程的影响开展了室内实验,研究了鲢(Hypophthalmichthys molitrix)对藻类的滤食效率,测定了滤食过程中鲢对磷的吸收和排泄,并分析了排泄对水体中氮、磷的影响。结果表明:(1)鲢通过滤食作用降低了藻类密度,且对不同藻类的滤食效率无显著差异;(2)在水体中,鲢滤食藻摄入磷并排泄溶解性磷(SRP),在食物充足时可维持水体总磷(TP)相对稳定,在食物不充足时,鲢消耗自身营养并持续排泄SRP,成为新磷源;(3)鲢摄入食物后以高氮磷比(N﹕P)向环境再供应无机营养,食物中大部分氮和少部分磷以无机营养形式排泄,使滤食组水环境N﹕P显著高于control组,其中滤食蓝藻组水环境N﹕P显著高于硅藻、绿藻组,提示鲢对藻的滤食促进水体营养向磷限制转换,尤其是滤食蓝藻可能加强这种趋势。总之,鲢不仅可通过摄食压力降低藻密度,同时能以高N﹕P排泄再分配营养影响藻生长,其对水体营养循环的作用值得关注。

不同鲢鳙配比对池塘浮游植物群落结构特征及水质的影响

为探究不同鲢鳙配比的多品种混养池塘对水体浮游植物群落结构和水质的影响,设置鲢、鳙配比为1∶1(A组)、3∶7(B组)和1∶9(C组)3个试验组,每组设2个重复(A1、A2,B1、B2,C1、C2),同时配养相同密度的青、鲫、鲤、鲮鱼和胡子鲇,养殖周期194 d。结果表明:3组试验塘7次采样共鉴定出浮游植物6门53属,其中绿藻门最多,占总种类数的40.3%;浮游植物总密度在(30.07~123.83)×10^(4)个·L^(-1)之间,生物量在0.49~2.51 mg·L^(-1)之间。多样性指数H显示,B组为轻污染,A、C组为β-中污染;均匀度指数J显示,A组为重污染,B、C组为α-中污染;丰富度指数D显示,A、B、C组均为轻污染。在3组养殖水体中,B组CODMn和TN含量较低,水质达标率最高。综上,鲢鳙配比为3∶7的多品种鱼类混养淡水池塘有利于浮游植物群落的多样性和水体生态健康。

发酵鲢鱼鱼糜香肠加工工艺优化及品质分析

以混合菌种(清酒乳杆菌、木糖葡萄球菌)作为发酵剂,以感官评分和pH为指标,采用正交实验优化发酵鲢鱼鱼糜香肠的加工工艺,并对产品进行指标测定。结果表明,当发酵剂接种量为3%,在30℃下发酵18 h时,所得产品香味浓郁,组织紧密,色泽均匀,口感良好,无异味。与未发酵香肠对比,在此条件下制得的发酵香肠的pH显著降低,氨基酸态氮含量升高,产品的色泽和质地得到明显改善,风味物质增加,尤其是芳香化合物和醇类化合物。该研究为发酵鱼糜制品的深入研究提供了一定的理论基础,为工业化生产提供了参考。