Prebiotic effect of glycerol galactoside isolated from color-faded nori in rats

Glycerol galactoside (GG; floridoside: 2-O-glycerol-α-d-galactopyranoside, and isofloridoside: 1-O-glycerol-α-d-galactopyranoside) is known to be a component of edible red seaweed nori. Recently, we have found that low-quality nori (color-faded nori), which has a low protein content, contains a large quantity of GG. From further studies, we have also found that GG has prebiotic characteristics in vitro. In this study, we evaluated the in vivo prebiotic activity of GG in rats. Dietary GG selectively increased the cecal Bifidobacterium count in rats. Other indices of prebiotics, such as pH of cecal content, organic acid concentrations, and fecal weight, also supported the existence of prebiotic activity of GG. The present data will also contribute to the development of a new method of utilizing color-faded nori as a health-promoting foodstuff.     

Identification of currently cultivated Porphyra species by PCR-RFLP analysis

ABSTRACT:   Porphyra yezoensis and P. tenera are the representative species of the marine crop Porphyra (nori) in Japan. Since the two species are extremely similar to each other in morphology, nori breeders have tentatively classified many strains of cultivated Porphyra into the two species without strict species identification. In order to facilitate rapid and reliable identification of the many strains of Porphyra currently cultivated in various Japanese regions, 24 conchocelis strains were examined by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis using the plastid RuBisCo spacer and the nuclear internal transcribed spacer regions. From the results, all the strains were identified as P. yezoensis f.  narawaensis , and P. tenera was not detected. Hence, it was confirmed that most of the Porphyra strains currently cultivated in Japan are P. yezoensis f.  narawaensis , and that intensive selective breeding has led to a reduced genetic diversity in the stock used for nori cultivation.     

Use of <Emphasis Type="Italic">Porphyra</Emphasis> spheroplasts as feed additive for red sea bream

ABSTRACT:   Two test diets with and without 5% Porphyra spheroplasts (PS) were formulated using white fishmeal as the main protein source. Red sea bream Pagrus major (mean body weight 15.4 ± 0.1 g) were maintained in a flow-through system (100 L) of thermo-controlled sea water (salinity 32–34, 25°C, 8 L/min) with ordinary aeration (400–600 mL/min) under laboratory light conditions (light–dark 12 h:12 h). Fish were fed three times a day at 10:00, 14:00 and 18:00 hours by hand for 42 days at 6% body weight on each experimental diet. Studies revealed that growth performance, survival and nutrient retention were significantly ( P  < 0.05) higher in the groups fed a diet containing spheroplasts (PS diet). Further, the fish fed the PS diet showed significantly ( P  < 0.05) lower feed conversion rates. Both groups of the PS and control diets had similar levels of body nutritional profile in terms of proximate compositions and fatty acids without compromising blood serum related parameters. From these experimental results, thus, it is comprehensible that a supplementary diet containing Porphyra spheroplasts can be used for maximizing not only growth of P. major but also for utilization of the feed ingredients.     

Preparation and characterization of fermented seaweed sauce manufactured from low-quality nori (dried and fresh fronds of <Emphasis Type="Italic">Pyropia yezoensis</Emphasis>)

The present study tested processes to manufacture fermented sauce from low-quality nori (dried and fresh fronds of Pyropia yezoensis). The nori sauce was prepared using three tanks with fresh or dried nori cultured in different conditions. In the present study enzymes were not added for the promotion of the degradation of nori, while in a previous study they were. The supernatants of culture mashes obtained from the three tanks were combined, and this low-quality nori sauce (LNS) was characterized and compared with sauces manufactured from high-quality nori, soy, and fish. The LNS showed low concentrations of total nitrogen compounds (0.20 g/100 ml) and free amino acids, and its taste showed a high sourness score as evaluated by a taste-sensing system. On the other hand, the LNS was rich in polysaccharides, which were observed to be readily degraded to lower molecular weight size sugars by heat treatment. The LNS showed little risk for heavy metal or allergen contamination. The obtained sauce product is expected to be commercially utilized as a component of low allergen-risk sauce products after blending with other seasonings without wheat or soy elements.     

Discrimination of excellent-grade ‘nori’, the dried laver Porphyra spp., with analytical methods for volatile compounds

Analytical methods were investigated for the discrimination of ‘nori’, the dried laver Porphyra spp. sheet products, which were organoleptically judged as excellent-grade for commercial distribution. Volatile compounds of nori were analyzed with an electronic nose and a gas chromatography-mass spectrometer (GC/MS) with headspace solid-phase micro-extraction. Each chopped dry nori sample was sealed in a vial and the headspace gas at 40 °C was analyzed. Excellent-grade nori product of ‘Akime’, first autumn shoots, of one season could be discriminated from other products by using principal component analyses (PCA) for the electronic nose response. PCA using a peak area of 32 compounds detected in the GC/MS analysis clearly discriminated all excellent-grade samples from all other samples. Excellent-grade products were considered to be characterized by higher total contents of 6-methyl-5-hepten-2-one, octanal and trimethylamine, and by lower total volatile contents, especially 1-pentanol, 2-pentenal, (E)-2-hexenal, acetoin, 2-methyl-2-butenal, 3-methyl butanal and others. These findings revealed the possibility of analytical discrimination of excellent-grade nori products as a substitution for organoleptic testing.     

Origin identification of dried seaweed product “nori” by PCR–RFLP analysis of Pyropia yezoensis in the internal transcribed spacer ITS-1 region

Nucleotide sequences in internal transcribed spacer (ITS)-1 region derived from dried nori products produced in Japan, China, and the Republic of Korea were compared. Thalli contained in the Japanese products were genetically homogenous, and their nucleotide sequences in ITS-1 were identical to those of the reference strains of Pyropia yezoensis f. narawaensis. In Chinese products, the thalli were related to P. yezoensis strain Minomiasakusa. In contrast, the thalli in the Korean products were genetically heterogeneous, and several different P. yezoensis strains and other Pyropia spp. were used for dried nori products. In some thalli produced in both China and Korea, the DNA sequences of the ITS-1 region were identical with that of Japan, suggesting that the cultivar strains might have been transplanted from Japan to China in recent years. The 432-bp-long nucleotide sequences in the ITS-1 region of thalli derived from Japanese origin were cleaved to two restriction fragments at 154 and 278 bp by cleavage of PCR-amplified products using MspI. Conversely, almost all of the corresponding sequences derived from China and Korea were lacking MspI or other restriction patterns, except for nori products from some areas that cultivate a closely related strain to the Japanese cultivar.     

Genetic characterization of a spontaneous green-type pigmentation mutant of Porphyra yezoensis and the significance of using heterozygous conchocelis in nori farming

ABSTRACT: In order to characterize the spontaneous green-type pigmentation mutant of Porphyra yezoensis , growth and contents of photosynthetic pigments were compared with those of the wild type in gametophytic blades. The growth of the green mutant was slower than that of the wild type. The content of phycoerythrin was markedly lower in the green mutant than in the wild type. For genetic analysis, the green mutant was crossed with the wild type. In the cross, the heterozygous conchocelis (the wild-type color) produced many sectored F ₁ gametophytic blades, which were composed of both parental colors. The segregation ratio by counting the wild-type sectors and the green-type sectors of the F ₁ blades was approximately 1 : 1. This suggests that the green mutant is governed by a single recessive gene. All the monospore germlings from the sectored F ₁ gametophytic blades that originated from the heterozygous conchocelis developed into single-colored blades with either the green color or the wild-type color. The advantages of using heterozygous conchocelis (hybrid conchocelis) and monospores from F ₁ gametophytic blades that originated from the heterozygous conchocelis in commercial farming of Porphyra yezoensis are detailed and discussed.     

Effect of taurine supplemented practical diet on growth performance and taurine contents in whole body and tissues of juvenile Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

ABSTRACT:   The effect of dietary taurine on juvenile Japanese flounder was determined by feeding three taurine-supplemented experimental diets (TAU) and a commercial diet (CD) to evaluate a practical diet for juvenile Japanese flounder. Juvenile Japanese flounder were reared on the three experimental diets supplemented with taurine at 0, 0.5, 1.0% and CD. These diets were fed to juvenile Japanese flounder of an initial mean body weight of 0.2 g for 6 weeks at 20°C and the taurine contents of the whole body and tissues were analyzed. The final average body weight of juvenile Japanese flounder fed the 1.0% TAU was significantly higher than that of the other groups. Taurine contents in the whole body and tissues increased with the increase in dietary taurine level. These results indicate that juvenile Japanese flounder require at least 15 mg/g taurine in the diet, even though a combined mix of fish, krill and squid meal was the main protein source in the experimental diets.     

Supplemental effect of <Emphasis Type="Italic">Porphyra</Emphasis> spheroplasts on the growth and feed utilization of black sea bream

ABSTRACT:   A 56-day feeding trial was conducted to evaluate the effects of Porphyra spheroplasts (PS) as a feed additive on growth, carcass composition and feed utilization of black sea bream. Four experimental diets with or without PS (0, 1, 3, 5% inclusion level) were formulated to determine the proper incorporation level for best growth and utilization using white fishmeal as the principal protein source. Three replicate groups of fish averaging 1.28 ± 0.05 g (mean ± SD) were maintained in flow-through thermo-controlled sea water (32–34 psu, 25°C) aquaria (100 L) under the laboratory conditions (L12 : D12) and fed three times a day at 09:00, 13:00 and 17:00 hours by hand at approximately 3% body weight on each diet. The rearing trial revealed that growth performance (in terms of weight gain, specific growth rate) are almost the same level in all the dietary groups, nevertheless the survival, nutrient utilizations and retentions (feed efficiency, protein efficiency ratio, protein retention rate, lipid retention rate) were significantly higher ( P  < 0.05) in a group fed on the diet containing 3% spheroplasts. Further, the fish fed on the diet containing PS had significantly higher ( P  < 0.05) crude lipid level in their dorsal muscles and viscera. The fish fed a PS-based diet showed higher level of eicosapentaenoic acid and docosahexaenoic acid (DHA) in viscera and DHA in dorsal muscles. The results obtained in this feeding trial suggest that the optimum dietary PS supplementation level up to 3% for black sea bream can be considered as improved consequence on growth performance, nutrient utilization or body composition were noticed.     

条斑紫菜烤制前后特征风味变化研究

为探讨烤制对条斑紫菜(Porphyra yezoensis)主要风味物质的影响,研究烤制前后条斑紫菜挥发性成分的变化。采用电子鼻、FlavourSpec®风味分析仪和固相微萃取–气相色谱–质谱联用(SPME-GC-MS)对比分析条斑紫菜在烤制前后挥发性风味物质的组成变化。电子鼻分析结果显示,条斑紫菜烤制前后的挥发性成分存在一定差异,二者的第一、二主成分相同,均为烃类、含氮类物质,但其对主成分的贡献率不同。风味分析表明,条斑紫菜烤制前后挥发性成分差异显著,烤制后出现吡嗪类特征风味物质。SPME-GC-MS分析表明,醛类、醇类、酮类和烷烃类构成了条斑紫菜的主体风味,烤制后吡嗪、甲基吡嗪、2,5-二甲基-吡嗪、2-乙基-5-甲基-吡嗪、3-乙基-2,5-二甲基-吡嗪和2-乙基-6-甲基-吡嗪等物质含量显著增加。综上所述,经过烤制,构成条斑紫菜的主要风味物质发生了明显变化,其中吡嗪类物质的相对含量显著增加。     

Paralytic shellfish poisoning toxin analysis of the genus <Emphasis Type="Italic">Alexandrium</Emphasis> (Dinophyceae) occurring in Korean coastal waters

ABSTRACT:   Paralytic shellfish poisoning (PSP) toxins produced by Alexandrium isolates from Korea were analyzed by high-pressure liquid chromography. Species designation of the regional isolates was determined by morphological criteria and ribotyping inferred from sequences of the 28S rDNA D1-D2 region. Toxin analysis performed at the exponential growth phase, revealed that the two strains of A. fraterculus were non-toxic, while the strains of A. tamarense and A. catenella were toxic. Toxic isolates DPC7 and DPC8 of A. catenella produced GTX1, 2, 3, 4, 5, dcGTX2, 3, C1, 2, neoSTX and STX with trace or non-detectable levels of C3 and C4, while isolates UL7, KDW981, SJW97043, SJW97046, KJC97111 and KJC97112 of A. tamarense produced GTX1, 2, 3, 4, dcGTX3, C1, 2, neoSTX with trace or non-detectable levels of C3, 4, dcSTX and STX, and no GTX5 and dcGTX2. The major toxins produced by A. catenella were C1 +2, and those of A. tamarense were C1 +2 and GTX4 in most of the isolates. A. tamarense strains other than SJW97046 produced a relatively high proportion of carbamate toxins, reflecting the high toxicity scores of shellfish intoxication in sampled coastal areas. Two representative toxic isolates, A. tamarense SJW97043 and A. catenella DPC7, were cultured for 30 days in batch mode and subjected to toxin analysis at 5-day intervals. Comparison of toxin productivity in terms of total toxin content, toxin components, and their variations with culture age revealed marked differences between the two strains.     

Preparation of nori Pyropia yezoensis enriched with free amino acids by aging the culture with nori koji

Koji is commonly used in manufacturing Japanese fermented products and promotes enzymatic degradation. In recent years, a seaweed koji has been developed by culturing Aspergillus oryzae on nori Pyropia yezoensis. In the present study, we prepared nori koji by culturing A. oryzae on high- and low-quality noris and then mixing this preparation with additional dried nori. Suitable fermentation conditions for increasing the taste-active components of the nori mixed with nori koji were investigated. The mixture of nori and koji prepared from high-quality nori, with added water, cultured for 120 days at 10 °C, provided the greatest increase (7 times) in free amino acids. The changes in taste after culturing the nori and koji mixture were evaluated using a taste-sensing system. The sourness score of the nori and koji mixture increased significantly, but the scores for other attributes such as bitterness and umami richness did not increase after culture. The present study has demonstrated a clear increase in the free amino acid content of nori and a modification in the taste score by aging the culture with nori koji. These results will encourage the development of ‘aged seaweed,’ a novel value-added product with nutritional and taste elements modified using seaweed koji.

     

A partial substitution of microalgae with single cell detritus produced from seaweed (Porphyra haitanensis) for the nursery culture of tropical oyster (Crassostrea belcheri)

Oyster seed production in hatchery and nursery systems has relied on the production of microalgae, which is cost effective, but often unpredictable. The development of a satisfactory substitute diet would greatly reduce production costs of hatchery operations. Single cell detritus (SCD) production from seaweed (Porphyra haitanensis) may have great potential as a partial substitute for microalgae. In this experiment, a technique for producing SCD was developed and the product was used as a partial substitute for microalgae for the nursery culture of juvenile tropical oysters (Crassostrea belcheri) in a hatchery setting. A reverse osmosis technique was used on ground seaweed (particle size <200 μm) immersed in freshwater and placed on a shaker at 100 rpm for 2 h before being returned to seawater. This technique was shown to be highly effective for SCD production with a density of 33.7 ± 7.0 × 10⁴ cell mL^?1 and the percentage of SCD particle diameter <20 μm was 89.2%. A partial replacement of microalgae with SCD was found to be unsuitable for nursing oyster larvae. For juvenile oysters (shell width 1.85 ± 0.03 mm and shell length 1.78 ± 0.06 mm) substituting 75% of microalgae with SCD showed lower absolute shell growth, and lower daily yields and survival rates when compared to rates substituting 50% or lower substitution with SCD, or 100% microalgae (P < 0.05). It was found that substituting 50% of the traditional microalgae with SCD produced from seaweed (P. haitanensis) can be used as a partial microalgae substitute for the nursery culture of the juvenile tropical oyster.     

Effect of dietary taurine and lipid contents on conjugated bile acid composition and growth performance of juvenile Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

ABSTRACT:   The effects of dietary taurine levels and lipid contents on the conjugated bile acid composition and growth performance of juvenile Japanese flounder Paralichthys olivaceus were investigated. Six types of diet (three different levels of taurine at two different levels of lipid) were fed to juveniles (average body weight, 0.04 g). Fishmeal that was washed with 70% ethanol to remove taurine was used as the sole protein source. Feeding experiments were carried out at 20°C for 6 weeks. At the end of the experiments, fish were weighed and analyzed for free amino acids in the body and the composition of the conjugated bile acids. The body weight and percent weight gain of the juveniles were improved by the dietary taurine supplementation. The taurine contents of the whole body and tissues increased with the increase of the dietary taurine contents. The conjugated bile acids in the gall bladder consisted of taurocholic acid and taurochenodeoxycholic acid, which increased with the increase of the dietary taurine level. Taurocholic acid accounted for more than 95% of the total conjugated bile acids. This indicates that taurine is the sole amino acid to conjugate bile acid in Japanese flounder.     

Characterization of the quantitatively major collagen in the mantle of oyster <Emphasis Type="Italic">Crassostrea gigas</Emphasis>

ABSTRACT:   A quantitatively major collagen was isolated from the pepsin-solubilized collagen preparation of the mantle by differential salt precipitation and phosphocellulose column chromatography, and its constituent α components (α1 and α2) were purified by phosphocellulose column chromatography. The subunits were demonstrated to be genetically distinct from each other by peptide mapping and amino acid analysis. The amino acid composition calculated from those of the α1 and α2 components in 2 : 1 ratio coincided well with that of the major collagen from the mantle. These results suggest that the major collagen in the mantle of the oyster may have a heterotrimer structure (α1)₂α2.     

Dietary value of benthic diatoms for post-larval abalone <Emphasis Type="Italic">Haliotis diversicolor</Emphasis> associated with feeding transitions

ABSTRACT:   The feeding behavior and growth of post-larval Haliotis diversicolor with initial shell lengths (SL) of approximately 500 μm (Exp. 1-1 and 1-2), 800 μm (Exp. 2), and 1200 μm (Exp. 3) were studied in a laboratory setting while they fed on four species of benthic diatom Achnanthes longipes , Cocconeis sublittoralis , Cylindrotheca closterium , and Navicula ramosissima . Exp. 1-1 and 1-2 revealed no marked differences in post-larval growth rates (mean 24–39 μm SL/day) among the diatom species. However, marked differences in growth rates among the species were revealed in Exp. 2 and 3. Three species, A. longipes , Co. sublittoralis, and Cy. closterium , produced faster growth (Exp. 2 mean 29–51 μm/day, Exp. 3 mean 36–44 μm/day) than N. ramosissima (Exp. 2 mean 18 μm/day, Exp. 3 mean 23 μm/day). Post-larvae fed N. ramosissima had lower digestion efficiency (42.8%) than those fed other diatom species (90.7–100%). Diatom extracellular substances appeared to be principally used from post-settlement to 800 μm SL, and diatom cell contents were required to produce rapid growth of larger post-larvae (>800 μm SL). It is likely that the availability of each diatom for post-larvae was affected by diatom morphology, attachment strength, frustule strength, and post-larval size.     

草鱼PRL基因多态性与幼鱼生长性状和肌肉成分的关联分析

为了探索草鱼(Ctenopharyngodon idella)PRL(prolactin)基因多态性与草鱼生长性状和肌肉成分的关联性,通过测序法从10尾草鱼的PRL基因中筛选到6个突变率高于30%的变异位点,包括5个单核苷酸变异位点和1个插入型突变(–/CACTCACTA),分别命名为2551GA、2639GC、3247AG、5197TG、5897GA和3391–+。利用AS-PCR(allele-specific PCR)和基因分型技术对192尾4月龄草鱼的PRL基因变异位点进行检测;基于一般线性模型对变异位点多态性与草鱼生长性状和肌肉成分进行相关性分析。研究发现,2639GC、3391–+和5197TG对体长和体重具有显著影响(P0.05),2639GC对肌肉粗蛋白含量具有显著影响(P0.05)。单个位点基因型比较发现,3391–+的突变型(–+和++)个体的体长和体重均显著高于野生型(––)个体(P0.05);2639GC的GC及5197TG的突变型(TG和GG)个体的体长和体重分别显著低于2639GC的GG和5197TG的TT野生型(P0.05);2639GC突变型(CC)个体的粗蛋白含量显著高于2639GC其他基因型(GG和GC)个体(P0.05)。两位点组合比较发现,含3391–+突变型(–+和++)的组合对应体长和体重普遍高于其他组,含2639GC的CC突变型的组合对应粗脂肪含量和粗蛋白含量普遍较高,其中粗蛋白含量显著高于其他组(P0.05)。研究表明,草鱼PRL基因多态性与草鱼生长性状和肌肉成分间存在显著关联,推测相关变异位点可作为草鱼生长和肉质改良的候选辅助标记。     

Changes of proximate compositions and myoglobin content in the dorsal ordinary muscles of the cultured Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis> with growth

ABSTRACT:   Using the dorsal ordinary muscle (DOM) of cultured Pacific bluefin tuna (body length [BL]: 47.5–81.8 cm, body weight [BW]: 2.1–13.5 kg, n  = 15), the changes of proximate compositions and myoglobin (Mb) content with growth were investigated. There was a positive correlation ( r  = 0.9832, P  < 0.05) of BL and BW in cultured tuna. The protein contents of the DOM of cultured tuna decreased ( P  < 0.05) and the lipid contents had a tendency to increase (not significantly) with growth. The meat color changed from pink to red with growth. In addition, the Mb contents of the DOM of cultured tuna increased ( P  < 0.05) from 1.0 mg/g (minimum BW fish) to 3.8 mg/g (maximum BW fish) with growth. These results indicate that the increase of the Mb content in the DOM of cultured tuna is not caused by the restriction of exercise and overfeeding between 2.1 kg and 13.5 kg of BW.     

Monthly assessments of proteins, fatty acids and amino acids in Artemia franciscana cultivated in 'Las Salinas de Hidalgo', state of San Luis Potosí, Mexico

This study presents the biochemical contents of Artemia biomass produced in a pond in 'Las Salinas de Hidalgo', State of San Luis Potosí, Mexico. The culture was realized over a period of 1 year in an 80 × 50 × 0.65 m (200 m³) pond. The feed consisted of a mixture of four micro algae. Samples of 1 kg of Artemia biomass (wet basis) were taken monthly and total protein, total lipid, amino acids and fatty acids were assessed. The contents of total protein and lipids showed a similar tendency from July to December (maintained values of about 300 mg g⁻¹ for protein and 90 mg g⁻¹ for lipids). With the exception of methionine and arginine, other seven indispensable amino acids were detected in the monthly samples, having similar values during the period from July to December. The most common fatty acids determined were the C16, C18, C18:1 and C18:3 n 6. Both, C20:4 n 6 and C20:5 n 3, were observed occasionally, but in high quantities. The use of the four micro algae as food for the Artemia cultured extensively, improved the biochemical composition and allows using this crustacean as feed for several species of aquatic organisms used for ornamental or human consumption.     

Effects of red clover extract on growth performance and body composition of African catfish <Emphasis Type="Italic">Clarias gariepinus</Emphasis>

ABSTRACT:   The present study was conducted to investigate the effects of the red clover extract on growth, body composition and survival of African catfish Clarias gariepinus . Three concentrations (25, 50 and 75 mg/kg) of red clover at dietary were used for 120 days. The final weights of red clover-treated groups were significantly different from each other and the control group. The best growth was observed in the group receiving the 75 mg/red clover kg diet. Fish fed with all levels of red clover had higher weight gains than the control. The highest values of the specific growth rate and the food conversion rate were 1.14 ± 0.01 and 2.26 ± 0.04, respectively, for the 75 mg/red clover kg diet group. During the red clover administration period, the survival ranged from 97.78% for the 50 p.p.m. group to 95.56% for the 25 and 75 p.p.m. groups. Protein contents of the dosage groups were significantly different from control ( P  < 0.05). The highest value of protein content (19.97%) was observed for the 75 mg/ red clover kg diet. Lipid and ash contents were significantly affected by the red clover levels in the diets. The highest lipid contents were in the 75 mg/red clover kg diet (4.67%), and the highest ash content was 1.39% for the 25 mg/red clover kg diet.