The influence of nitrogen and phosphorus on the growth of a diatom Skeletonema costatum (Greville) Cleve

Nitrogen and phosphorus requirements of a chain-forming diatom, Skeletonema costatum (Greville) Cleve, collected from Yatsushiro Sea, Japan, were investigated in a laboratory culture experiment. Sodium nitrate and sodium glycerophosphate were used as nitrogen and phosphorus sources, respectively. Cultures were grown in modified Provasoli's ASP2NTA medium (Provasoli et al. 1957) at 25±1°C, light intensity 60 µE mˉ² secˉ¹ and photoperiod 12:12-h, L:D cycle. Optimum growth was observed at nitrate concentrations of 3-10 mglˉ¹ and phosphate concentrations of 1.5-15 mglˉ¹. Adequate growth was also found at the nitrate concentration of up to as high as 300 mglˉ¹. Significantly poorer growth was found at lower nitrate (<3.0 mglˉ¹) and higher phosphate (>15 mglˉ¹) concentrations. From the present study, it is concluded that S. costatum can grow well at wide ranges of nitrate concentrations but is sensitive to higher phosphate concentrations.

Observations on changes in the major protein nitrogen fraction of prawns and sardines during ice storage

Changes in the major protein nitrogen fractions (sarcoplasmic, myofibrillar, stroma) have been studied in two species of prawns and in oil sardine held in ice storage. Myofibrillar proteins were observed to get denatured at a rapid rate as determined by salt extractability method. The sarcoplasmic proteins were not denatured to any considerable extent. With sardine however, the extraction of myofibrillar proteins was inhibited rather in the uniced condition itself presumably owing to the presence of free fatty acids.

Effects of physiological doses of vitamin D sub(3) (Cholecalciferol) on induced molting and growth in giant freshwater prawn, Macrobrachium rosenbergii (de Man)

Effects of three different doses of vitamin D sub(3) on molting, growth, and calcium and phosphate composition of tissue and molt during the grow-out of the giant freshwater prawn Macrobrachium rosenbergii (average weight 10.56 ± 0.20 g), obtained from a grow-out pond, were studied. Intramuscular doses of vitamin D sub(3) (100, 500 and 2000 IU/kg body weight) were given on the 1st, 3rd, 5th, 7th, 9th, 11th, 13th, 15th, 20th, 25th and 30th days. All the experimental animals were fed with a basal diet containing fish meal, shrimp meal, wheat flour, groundnut de-oiled cake, soybean meal and wheat bran at 3% of the body weight. The numbers of molts were recorded as 20±0.50, 29±1.16, 51±1.87, and 30±1.60 in control, 100, 500 and 2000 IU/kg body weight physiological doses, respectively. Maximum growth was recorded in prawns given 500 IU/ kg dose. Survival was between 58.33 ± 9.13 and 77.77 ± 8.61%. The ash content and calcium level increased significantly (p<0.05) and recorded the highest values in 500 IU/kg physiological dose. However, the inorganic phosphate (P sub(i)) content recorded the highest values in tissue in 2000 IU/kg dose (p<0.05, F = 50.60613). There is no significant difference in calcium contents (p>0.05) in both tissue and molt at 500 and 2000 IU/kg doses. It was found that a higher physiological dose (2000 IU/kg) of vitamin D sub(3) increased the rate of mortality. Results have shown that vitamin D sub(3) has a positive impact on the growth and survival of M. rosenbergii and it interferes with the metabolism of Ca and P sub(i), in tissue, and alters molting frequency. Results on physiological dose suggest an alternative and effective dietary supplementation method of vitamin D sub(3) in the grow-out phase of M. rosenbergii.

Effects of gamma radiation on nutritional and microbial quality of Pampus chinensis (Euphrasen 1788)

To evaluate the efficiency of gamma radiation in combination with low temperature Chinese pomfret, Pampus chinensis were preserved by the treatment of different doses of gamma radiation (3, 5 and 8 KGy) at freezing temperature (-20°C) during 90 days of storage period. Quality assessments for fish were carried out at an interval of 15 days during the storage period. Quality assessments were done by organoleptic, chemical (Total Volatile Nitrogen, TVN and Trimethylamine, TMA) and microbiological (Total Bacterial Count, TBC and Total Mould Count, TMC) evaluation. From the analysis of all parameters, maximum shelf-life was observed for irradiated (8 KGy) sample. It remained acceptable up to 75 days and that was the highest duration among 4 types of samples.

Effect of carp PG doses on induced breeding of Shing, Heteropneustes fossilis (Bloch)

Five hormone doses viz. 25, 50, 75, 100, and 125 mg of carp PG/kg of body weight of the recipient fish were tested and they were designated as T1 T2, T3, T4, and T5 respectively. Significantly higher fertilization (98%) and hatching rates (38%) were obtained from T3 (75 mg of carp PG extract/kg body weight). While T4 (100 mg of carp PG extract/kg body weight) and T5 (125 mg of carp PG extract/kg body weight) gave the highest (90%) ovulation rate. In June and July the highest fertilization rate of 96 and 96.4% respectively and hatching rate 42.5 and 48.7% respectively were obtained. In over all consideration carp PG extract at a dose of 75 mg/kg body weight appears to be the suitable dose for induced breeding of H. fossilis and June and July are the suitable time for its induced breeding.

Influence of nitrogen salts on growth and physiological responses of Rhizophora apiculata Blume in non-aerated water culture

Influence of two different forms of nitrogen on growth and physiological aspects of water-cultured seedlings of Rhizophora apiculata was studied. Of the two forms of nitrogen supplied to the growth medium, ammonium nitrogen was better than nitrate nitrogen by exhibiting increased dry matter production, shoot length, leaf area and also enhanced the contents of carotenoids, chlorophylls and their presence in photosystems and light harvesting protein complex.

Nitrogen-fixing aerobic bacteria and their nitrogenase activity in north Mumbai coastal waters

The effect of the physicochemical parameters of water and soil on the distribution of nitrogen-fixing bacteria and their nitrogen-fixing capacity was studied. Four species of nitrogen-fixing bacteria, e. g. Azotobacter chroococcum, A. vinelandii, A. beijerinckii and A. armeniacus, were recorded from water and soil samples of Mumbai coast. A higher number of bacterial populations were observed in sediment than in water samples. A positive correlation was observed between the dissolved organic matter and nitrogen fixing bacterial populations of water as well as between available phosphorus and the nitrogen-fixing bacteria of sediment. The nitrogen-fixing capacity of A. chroococcum was found to be 1.076 nmol C sub(2) H sub(4)/l/d and that of A. vinelandii was 0.965 nmol C sub(2) H sub(4)/l/d. Station 1 showed higher level of nitrogenase activity in comparison to other four stations.

The free alpha amino acid nitrogen contents of some common food fishes of Kakinada region, Andhra Pradesh

The moisture and free alpha amino nitrogen contents of some important food fishes and shell fishes of Kakinada region have been studied. Crustaceans and molluscs contain free alpha amino acids in quantities several times higher than all other aquatic animals examined in this study. Their probable role in the physiological activities of these animals has been discussed.

Advantages of liquid nitrogen freezing of Penaeus monodon over conventional plate freezing

Liquid nitrogen frozen products are biochemically and organoleptically superior to conventional plate frozen products but beneficial effect of liquid nitrogen freezing over conventional plate freezing can exist only up to 59 days at a commercial storage temperature of -18°C.

Nitrogen fixing bacteria, Azotobacter sp. in aquatic sediment

Non-symbiotic, free living, nitrogen fixing bacteria, Azotobacter sp. was estimated in sediments of estuarine, marine, backwater and mangrove environments of Portonovo. Number of colony forming units (CFU) of Azotobacter sp. was less (5 to 27 cells/g of dry sediment). CFU of total heterotrophic bacteria (THB), actinomycetes and fungi were between 4.1x10 super(6) and 4.5x10 super (7), 0.8x10 super(5) and 4.9x10 super(5), 1.1x10 super(5) and 3.8x10 super(5)/g respectively. Mangrove sediments contained more CFU of the above microbial groups.

Effect of liquid nitrogen freezing and subsequent storage on survival of Staphylococcus aureus and Streptococcus pyogenes in treated prawn meat

Prawn meat treated with Streptococcus pyogenes B-49-2 culture and Staphylococcus aureus ATCC-12598 culture were frozen in conventional plate freezer at -40°C and by spray type liquid nitrogen freezer. The frozen products were stored at -18°C. Streptococcus pyogenes B-49-2 showed low sensitivity to cold injury during freezing and frozen storage. Staphylococcus aureus ATCC-12598 survived during the entire storage period of 240 days. Total bacterial count of untreated prawn meat was found to be always lesser in liquid nitrogen frozen products than that in plate frozen products.

Influences of dietary lipid and phosphorus levels on retention and excretion of phosphorus and nitrogen in fingerlings red sea bream, Pagrus major

A laboratory based 2x3 factorial experiment was conducted for 12 weeks to investigate the influences of dietary lipid and phosphorus (P) levels on retention and excretion of phosphorus and nitrogen (N) in fingerling red sea bream. Two levels of lipid (210 and 260 g/kg) and three levels of phosphorus (17, 14 and 12 g/kgˉ¹) in the dry diets were tested. Duplicate groups of 25 red sea bream (average weight 3.74±0.07 g) per 60L glass tank were fed experimental diets three times a day near to satiation level at 22 to 28°C water temperature. A reduction in dietary fish meal from 500 to 300 g/kg dry diet, corresponding to a supplementation in both dietary lipid and P resulted in significant increase in both P and N retention which resulted in the reduction of their excretion by red sea bream. The overall results of the present study demonstrated that both lipid and phosphorus supplementation are necessary for developing less-polluting feed which in turn, reduce fish meal level in the diet of fingerling red sea bream. Further studies in this regard with different size and age groups of red sea bream are warranted.

Effects of gamma radiation and -20°C temperatures on the shelf life of Hilsa, Tenualosa ilisha (ham.-Buch. 1822)

The combined effect of radiation and refrigeration on the shelf life of hilsa, Tanualosa ilisha was studied by monitoring the microbiological, chemical and sensory changes of unirradiated and irradiated fish samples using low dose irradiation, doses of 300 krad, 600 krad and 900 krad. Irradiation (900 krad) dramatically reduced population of bacteria, namely total viable counts 48.850cfu per gm for unirradiated, 31.850cfu per gm and 19.600cfu per gm of 300 krad and 600 krad, respectively. The effect was more pronounced at the higher dose (900 krad), total viable count were 14.100cfu per gm. Another microbial indicator total mould counts (TMC) was 8.750cfu per gm, 6.350cfu per gm, and 19.600cfu per gm for 300 krad and 600 krad, respectively. The effect was more pronounced at the higher dose (900 krad) where total viable counts were 14,100cfu per gm. Total volatile nitrogen values increased slowly attaining a value of 101.02mgN per 100gm for unirradiated T. ilisha during refrigerated storage, whereas for irradiated fish, lower values of 71.13, 59.33 and 47.03mgN per 100gm muscle were recorded. Sensory evaluation showed a good correlation with bacterial populations on the basis of overall acceptability scores.

Application of combined effect of sodium acetate and nisin on reduction of contamination by Listeria monocytogenes in vacuum packaged grass carp (Ctenopharyngodon idella) fillets kept at 4°C

In this study microbiological , chemical quality and fatty acid composition of grass carp (Ctenopharyngodon idella) fillets treated by dipping in sodium acetate (%1 and %3), nisin (% 0.1 and % 0.2) and combination of sodium acetate and nisin was evaluated during 16 days of refrigerated of 4°C Antilisterial effect of nisin was enhanced with the increased concentration of sodium acetate. At day 12 post storage, Listeria monocytogenese count was higher in the control group than the recommended value, however in sodium acetate and nisin treated samples, the count was lower (5.17-5.91 log cfu/g). With increasing the concentrations of sodium acetate, mesophilic counts were lower. Regarding nisin, better results was obtained by applying %0.1 nisin. Greater inhibition of mesophile bacteria was observed when combination treatment was used. The number of lactobacillus was lower when higher concentrations of sodium acetate and nisin were used. Total Volatile Nitrogen values at the end of the experiment were lower in the samples treated with both nisin and sodium acetate and the better results were obtained in combination treatments. Peroxide (PV) at the end of the experiment was 1.9 meq/kg in control, and the lowest values were observed for the treatments 3(%0 sodium acetate +% 0.2 nisin) and 9(%3 sodium acetate +% 0.2 nisin) between 1.08 and 1.62 meq/kg without significant difference. Thiobarbituric acid (TBA) levels at the end of experiment have been shown to be 0.46 mg malonaldehyde per kg in the control. On the other hand treatments 9 had the TBA values of 0.19 mg malonaldehyde per kg which was significantly lower than that of control. Polyunsaturated fatty acids increased by increasing the sodium acetate doses and instead saturated fatty acids and n-6/n-3 ratio decreased. The ratio of UFA/SFA and also C22:6/C16:0 increased when a higher concentration of sodium acetate has been used. The best result obtained by using 3% of sodium acetate but no such relation with nisin was observed.