光照、温度、碳源及接种密度对微绿球藻生长的影响

运用正交设计法开展了碳源和接种密度,光照、温度和接种密度对微绿球藻生长影响的试验。结果表明,在碳源和接种密度的试验中,NaHCO_3浓度、接种密度及其交互作用存在显著性差异,最优水平为NaHCO_32.5g/L、接种密度300×10~4个/mL。在光照、温度和接种密度试验中,各因子以及其一级交互作用均存在着显著性差异,最优水平是培养温度30±1℃、光强7000LX、接种密度100×10~～150×10~4个/mL。     

光合细菌培养基配方的优化研究

光合细菌培养基的组分是由乙酸钠、氯化铵、磷酸二氢钾、硫酸镁、酵母膏等5种原料构成。采用L16(45)正交表,将5种原料作为光合细菌生长有影响的因素,通过试验数理统计的直观和理论分析,对其配方进行优化。试验结果表明,当培养基的配方为乙酸钠3.3 g/L、氯化铵0.6 g/L、磷酸二氢钾0.9 g/L、硫酸镁0.5 g/L、酵母膏1.5 g/L、光照3 000 lx和温度(32±2)℃时,培养72 h即可达到生长峰值,细菌总数可以从起初的1.75×109cfu/mL提高到3.19×109cfu/mL。优化的培养基条件能有效促进光合细菌生长。     

产木聚糖酶菌株YS1069的产酶条件优化

为获得较高的木聚糖酶产量,采用单因素实验和响应面实验方法,筛选氮源、碳源、无机盐、接种量、装液量、Na2CO3、发酵温度、发酵时间多个单因素,对产木聚糖酶的芽孢杆菌YS1069的发酵培养基和发酵条件进行了优化.结果显示,豆饼粉25 g/L、麸皮40g/L、NaNO3 0.9 g/L、K2HPO43g/L、MgSO4·7H2O 0.6 g/L、接种量4％、装液量30 ml/250 ml(v/v)、Na2CO3添加量18 g/L、培养温度30℃、培养时间96 h时,酶活性达到最高.再通过Plackett-Burman设计对影响木聚糖酶产量的8个主要因素进行评价,确定Na2CO3浓度、麸皮浓度和MgSO4·7H2O浓度是影响产酶量的3个主要因素.利用中心组合设计及Design-Expert 8.05软件分析,获得了主要因素的最优条件,即Na2CO3浓度21.86g/L、麸皮浓度51.41 g/L、MgSO4·7H2O浓度0.59 g/L,实验最终酶活性比发酵优化前提高了5倍.     

产虾青素海洋酵母菌YS-185的鉴定及发酵条件优化

以26S rDNA法将实验室保藏的1株产虾青素的海洋酵母菌YS-185鉴定为粘红酵母。以海洋酵母菌YS-185为试验菌株,运用摇瓶发酵优化的方式,探索培养基组分和发酵工艺条件对该菌发酵的影响。实验结果表明,该菌生长最适培养基组分为葡萄糖8 g/L、蛋白胨8 g/L,最适生长起始pH值为5.5、转速220 r/min、接种量8%、温度20℃;虾青素合成的最佳培养基组分葡萄糖8 g/L、蛋白胨8 g/L,最佳虾青素合成条件:pH 5.5,转速220 r/min,接种量8%,培养温度25℃。发酵优化后的虾青素产量2.670μg/ml,较优化前的1.572μg/ml提高了69.8%。温度对酵母菌的生长和虾青素的合成都有显著影响。海洋酵母菌YS-185优化后的发酵条件有规模化生产虾青素的应用潜力。     

高原湖泊光合细菌处理水产养殖污水的初步研究

从星云湖中分离并挑选出4株光合细菌,用于水产养殖污水的处理。实验表明:使用混合菌株和固定化混合菌株对污水的净化效果要比使用单一菌株好;且在不同环境条件下处理效果也不同,光照优于黑暗,接种量控制在1~5 mg/L时,处理效果较好;当温度低于15℃、NaC l投加量超过2 g/L、CuSO4的投加量高于0.4 mg/L时,处理效果明显下降。     

海洋芽孢杆菌N11-8产蛋白酶的发酵条件优化

本研究采用响应面法(RSM)对南极海洋芽孢杆菌(Bacillus sp.)N11-8液体发酵产蛋白酶PBN11-8的发酵条件进行快速优化。通过单因素实验初步确定南极海洋芽孢杆菌N11-8产蛋白酶的最佳碳源和氮源分别为可溶性淀粉和蛋白胨；并通过Plackett-Burman(PB)设计对影响其产酶相关因素进行评估，筛选出具有显著效应的3个因素：温度、氮源和碳源；以最陡爬坡实验逼近至上述因子最大响应区域，进而采用RSM法对其最佳水平范围进行研究，确定最优发酵条件为：可溶性淀粉3 g/L，蛋白胨13.1 g/L，酵母浸粉2.9 g/L，NaCl 5 g/L，KH2PO4 1 g/L，FeCl3·6H2O 2 mmol/L，初始pH值为7.0，温度为34.0℃，转速为200 r/min，装液量为50 ml/250 ml，接种量为4%，培养时间为60 h。最终优化后的酶活达到90.5 U/ml，比初始酶活提高了23.6%。     

海洋红酵母RH1菌株发酵培养条件的研究

该研究比较了不同碳源、氮源、无机盐对海洋红酵母菌（Rhodotorula sp.）RH1菌株发酵产量的影响,通过葡萄糖、蛋白胨、酵母膏和硫酸镁（MgSO4）4因素3水平的正交试验,确定了RH1菌株的最优培养基为蛋白胨10 g.L-1,酵母膏15 g.L-1,葡萄糖20 g.L-1,MgSO40.25 g.L-1,磷酸二氢钾（KH2PO4）0.25 g.L-1,氯化钠（NaCl）10 g.L-1。结果显示,该菌株最佳摇瓶发酵条件为接种量10%,初始pH 5.0,摇瓶装液量80 mL/500 mL三角瓶,培养温度28℃,经48 h培养,菌量可达10.46×108cfu.mL-1,比优化条件前提高23.9%。还进行了RH1菌株25 L发酵罐扩大培养试验,在接种量为8%、初始pH 5.0、搅拌速率350～400 r.min-1、通气量9 L.min-1、温度28℃的条件下,经28 h的培养,菌量可达33.6×108cfu.mL-1。预计通过连续补料的方式进行培养,有望进一步提高菌量。     

室外培养参数对光合细菌生长的影响

本试验选择5L无色透明聚乙烯塑料瓶作为培养容器,接种后置于室外自然光源下进行光照培养。采用单因子优化试验探讨不同的光照度、初始pH值、初始接种浓度、氧需求程度、摇动次数等对光合细菌生长的影响。结果表明:其最适光照度6 000~8 000lx、初始pH值为7.0~7.5、最佳接种量为30%、厌氧培养、每天摇动1~2次,一般培养6d可使光合细菌活菌数≥4×109个/mL,杂菌率≤10%。     

光合细菌对多刺裸腹溞培养的影响

在实验室条件下,采用静止培养法对多刺裸腹溞进行培养实验,研究在以酵母和小球藻为饵料的多刺裸腹溞培养中,添加不同浓度光合细菌对其生长繁殖的影响。结果表明:光合细菌(菌液浓度为48×108cell/ml)添加量为1 mg/L(组2)、2mg/L(组3)、64 mg/L(组8)、130 mg/L(组9)和260 mg/L(组10)时,实验组中多刺裸腹溞的生殖量与空白对照(组1)相比均无差异(P>0.05);光合细菌添加量分别为4 mg/L(组4)和8 mg/L(组5)时,实验组中多刺裸腹溞的生殖量明显多于对照组,差异较明显(P<0.05),其对多刺裸腹溞的增长具有明显的促进作用;在16 mg/L(组6)和32 mg/L(组7)时,实验组中多刺裸腹溞的生殖量达到最高峰,分别为对照组的1.54倍和1.40倍,差异十分显著(P<0.05);而当添加量过高,在520~800 mg/L(组11~组14)浓度范围内,实验组中多刺裸腹生殖量呈现急剧下降趋势,显著低于对照组(P<0.05);在本实验设计范围内,浓度等于或高于900 mg/L(组15)时,幼溞在12 d后仍没有达到性成熟,光合细菌对多刺裸腹溞的繁殖明显起抑制作用。以上结果显示,在以酵母与小球藻为饵料的多刺裸腹溞培养中,16~32 mg/L的光合细菌添加量最为适宜,该浓度范围的光合细菌对多刺裸腹溞的生长繁殖具有显著的促进效果。     

抗弧菌光合细菌的分离鉴定及对氨氮和亚硝态氮的降解特性

该研究采用双层平板涂布法和划线法,从不同地区的海洋环境样品中分离纯化光合细菌,以副溶血弧菌(Vibrio parahemolyticus)、创伤弧菌(V.vulnificus)、鳗弧菌(V.anguillarum)为指示菌,采用牛津杯法测定海洋光合细菌菌株的抑菌作用,采用靛酚蓝分光光度法和盐酸萘乙二胺分光光度法测定不同菌株对氨氮(NH_4~+-N)和亚硝态氮(NO_2~--N)的降解作用,筛选出具有抗弧菌并高效降解NH_4~+-N和NO_2~--N复合功能的优良菌株。结果显示,从30个海水、海泥等样品中分离得到3株光合细菌,分离自连云港车牛山岛海水样品的菌株P-3,对3种弧菌均具有较强的抑制作用,其中对鳗弧菌的作用最强,抑菌圈直径为5.3 mm。3株光合细菌均具有一定的降解NH_4~+-N和NO_2~--N作用,菌株P-3的降解作用最强,在含有50 mg·L~(-1) NH_4~+-N和NO_2~--N的培养基中培养4 d,降解率分别为89.68%和94.98%。经形态学观察、生理生化试验和16S rDNA序列分析,确定P-3为沼泽红假单胞菌(Rhodopseudomonas palustris)。     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。     

Effects of Spirulina platensis as a feed additive on growth and coloration of blue dolphin cichlids (Cyrtocara moorii Boulunger, 1902)

This study was carried out to investigate the effects of replacing fish meal with dietary Spirulina as a feed supplement on the growth performance and coloration of blue dolphin cichlids (Cyrtocara moorii). Five isonitrogenous (47% crude protein) and isocaloric (17.36 kJ/g digestible energy) diets were for formulated to replace FM with 0, 5, 10, 15 and 20% Spirulina (designated as Control, SP5, SP10, SP15 and SP20 respectively) and fed to the fish (initial body weight, 3.15 ± 0.01 g). Fish were randomly distributed into fifteen 120 L aquariums (26.5 ± 1.00°C), 15 fish per aquarium. The diets were tested in triplicate for 12 weeks. Experimental groups were fed twice daily (09:00 and 17:00) by hand to satiation. At the end of the feeding trial, significantly (p < 0.05) higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and lower feed conversion ratio (FCR) were observed in fish fed the SP10 diet when compared to the SP20 diet. There was no significant difference in these parameters between the other groups. The skin coloration of blue dolphin cichlid fed a diet containing Spirulina meal was enhanced. The best coloration was observed in the SP15 group. These impressions were objectively validated by chemical determinations of carotenoids extracted from fish skins and passed statistical tests of significance. The study findings show that Spirulina meal does not diminish growth rates except at very high levels.     

A Minchinia mercenariae‐like parasite infects cockles Cerastoderma edule in Galicia (NW Spain)

The cockle Cerastoderma edule fishery has traditionally been the most important shellfish species in terms of biomass in Galicia (NW Spain). In the course of a survey of the histopathological conditions affecting this species in the Ria of Arousa, a haplosporidan parasite that had not been observed in Galicia was detected in one of the most productive cockle beds of Galicia. Uni‐ and binucleate cells and multinucleate plasmodia were observed in the connective tissue mainly in the digestive area, gills and gonad. The parasite showed low prevalence, and it was not associated with abnormal cockle mortality. Molecular identification showed that this parasite was closely related to the haplosporidan Minchinia mercenariae that had been reported infecting hard clams Mercenaria mercenaria from the Atlantic coast of the United States. The molecular characterization of its SSU rDNA region allowed obtaining a fragment of 1,796 bp showing 98% homology with M. mercenariae parasite. Phylogenetic analysis supported this identification as this parasite was clustered in the same clade as M. mercenariae from the United States and other M. mercenariae‐like sequences from the UK, with bootstrap value of 99%. The occurrence of M. mercenariae‐like parasites infecting molluscs outside the United States is confirmed.     

Dietary thiamin and pyridoxine requirements of fingerling Indian major carp,Cirrhinus mrigala (Hamilton)

Two experiments were conducted to quantify the dietary thiamin (experiment I) and pyridoxine (experiment II) requirements of fingerling Cirrhinus mrigala for 16 weeks. In experiment I, dietary thiamin requirement was determined by feeding seven casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) with graded levels of thiamin (0, 0.5, 1, 2, 4, 8 and 16 mg kg^?1 diet) to triplicate groups of fish (6.15 ± 0.37 cm; 1.89 ± 0.12 g). Fish fed diet with 2 mg kg^?1 thiamin had highest specific growth rate (SGR), protein retention (PR), RNA/DNA ratio, haemoglobin (Hb), haematocrit (Hct), RBCs and best feed conversion ratio (FCR). However, highest liver thiamin concentration was recorded in fish fed 4 mg thiamin kg^?1 diet. Broken‐line analysis of SGR, PR and liver thiamin concentrations exhibited the thiamin requirement in the range of 1.79–3.34 mg kg^?1 diet (0.096–0.179 μg thiamin kJ^?1 gross energy). In experiment II, six casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) containing graded levels of pyridoxine (0, 2, 4, 6, 8 and 10 mg kg^?1 diet) were fed to triplicate groups of fish (6.35 ± 0.37 cm; 1.97 ± 0.12 g). Fish fed diet containing 6 mg kg^?1 pyridoxine showed best SGR, FCR, PR, RNA/DNA ratio, Hb, Hct and RBCs, whereas maximum liver pyridoxine concentration was recorded in fish fed 8 mg kg^?1 dietary pyridoxine. Broken‐line analysis of SGR, PR and liver pyridoxine concentrations reflected the pyridoxine requirement from 5.63 to 8.61 mg kg^?1 diet. Data generated during this study would be useful in formulating thiamin‐ and pyridoxine‐balanced feeds for the intensive culture of this fish.     

Sea bream culture in Egypt; status, constraints and potential

Marine fish farming in Egypt began in 1976 with the culture of gilthead sea bream, (Sparus aurata) as this fish was notably adaptable to brackish and marine pond conditions. Today, marine fish and shrimp farms amount to about 19,000 ha, out of which 42% is already in production while the rest, i.e., 58% is still under construction. In 1997, cultured gilthead sea bream production of 2,250 tons made up 3% of the 75,000 tons total aquaculture catch. In polyculture, usually with the grey mullet and sea bass, gilthead sea bream contributed 440 kg ha^–1 to the total yield of 1,700 kg ha^–1 (26%) over a period of 16 months. For the same period, the yield of monoculture ponds averaged 100 kg ha^–1, while in marine cages, yields ranged from 4–10 kg m³. In 1996–1997, fry of 0.25–1 g and fingerlings 1–10 g with a total of 3 million, were collected from the wild and 1 million fry were produced in the three marine hatcheries out of the four existing ones. The development of sea bream culture in Egypt is now severely inhibited by the shortage of seeds and adequate feeds. Exports of both sea bream and sea bass, during 1994–1996 averaged 1,300 tons per year.     

Fertilization by refrigerator stored sperm of the Indian major carp, Labeo calbasu (Hamilton, 1822)

This study reports on the spermatological properties, and on the development of a protocol for refrigerator storage (4°C) of Labeo calbasu (Hamilton, 1822) sperm for artificial breeding. Volume, motility, concentration and pH of the freshly collected sperm were 2.21 ± 0.53 (μL g^?1 of fish weight) (mean ± SD), 95 ± 1 (%), 1.93 ± 0.44 × 10⁹ (cells mL^?1) and 7.56 ± 0.17 respectively. Sperm activation was evaluated at different osmolalities of NaCl solution, and motility ceased completely when osmolality of the extender was ≥287 mOsmol kg^?1. Sperm retained motility for 24, 72 and 108 h, after refrigerator storage when sperm were undiluted, suspended in Alsever's solution and suspended in Alsever's solution containing 5% methanol respectively. Fertilization rate of fresh eggs with sperm stored at 4°C in Alsever's solution and Alsever's solution containing 5% methanol was 77% and 60% with a hatching rate of 60% and 43% respectively. The fertilization and hatching success of the stored sperm suggests potential to use refrigeration for transporting genetic material to hatcheries for artificial breeding of L. calbasu in Bangladesh.     

A novel approach to denitrification processes in a zero-discharge recirculating system for small-scale urban aquaculture

This paper presents an innovative process to solve the nitrate build-up problem in recirculating aquaculture systems (RAS). The novel aspects of the process lie in a denitrification bioreactor system that uses solid cotton wool as the primary carbon source and a unique degassing chamber. In the latter, the water is physically stripped of dissolved gaseous O₂ (by means of a Venturi vacuum tube), and the subsequent denitrification becomes more efficient due to elimination of the problems of oxygen inhibition of denitrification and aerobic consumption of cotton wool. The cotton wool medium also serves as a physical barrier that traps organic particles, which, in turn, act as an additional carbon source for denitrification. Operation in the proposed system gives an extremely low C/N ratio of 0.82 g of cotton wool/g of nitrate N, which contributes to a significant reduction of biofilter volume. The additional advantage of using solid cotton wool as the carbon source is that it does not release organic residuals into the liquid to be recycled. Operation of the system over a long period consistently produced effluents with low nitrate levels (below 10 mg N/l), and there was only a very small need to replace system water. The overall treatment scheme, also incorporating an aerobic nitrification biofilter and a granular filtration device, produced water of excellent quality, i.e., with near-zero levels of nitrite and ammonia, a sufficiently high pH for aquaculture, and low turbidity. The proposed system thus provides a solution for sustainable small-scale, urban aquaculture operation with a very high recovery of water (over 99%) and minimal waste disposal.