Nile Tilapia Skin Research Articles

Isolation and characterisation of acid-solubilised collagen from the skin of Nile tilapia (Oreochromis niloticus)

Acid-solubilised collagen (ASC) was extracted from the skin of Nile tilapia (Oreochromis niloticus) and characterisation was studied. The results indicated that the yield of ASC was 39.4% on the basis of dry weight. This ASC was rich in glycine (35.6%). The amount of imino acids, proline and hydroxyproline, in ASC was 210 residues per 1000 residues. The ultraviolet (UV) absorption spectrum of ASC showed that the distinct absorption was at 220 nm. ASC showed transition curve at maximum temperature (Tmax) of 32.0 °C in 0.05 M acetic acid, about 12 °C lower than that of calf skin collagen. Maximum solubility (0.75 mg/ml) in 0.5 M acetic acid was observed at pH 3. Solubility reached the minimum at pH 7. A sharp decrease in solubility was observed in 2% (w/v) NaCl or above. Biochemical studies indicated that ASC was composed of the α1α2α3 heterotrimers.

Functional Properties of Grass Carp (Ctenopharyngodon Idella), Nile Perch (Lates Niloticus) and Nile Tilapia (Oreochromis Niloticus) Skin Hydrolysates

The influence of using an endo-peptidase (alcalase) on the functional properties of hydrolysis products from Nile perch, Grass carp, and Nile tilapia skin was studied. Reaction conditions were controlled at pH 8.25, 60°C, and the enzyme was added on the basis of standard activity units at an enzyme to substrate ratio of 1.7 g/100 g protein. The reaction was allowed to proceed for 85 min and enzyme was inactivated by heat. The soluble protein fractions were recovered and lyophilized. All freeze-dried fish skin hydrolysates powders had a light yellow color and contained up to 90% protein. Nitrogen solubility varied from 95.93 to 98.72% and was not significantly different at 5% probability level. The water and oil holding capacities of the skin hydrolysates were good in the range of 2.8 to 3.2 mL/g and 3.4 to 3.8 mL/g, respectively. Emulsification capacity varied from 11.3 to 21 mL/0.5 g with Nile perch skin hydrolysate having the highest score while Nile tilapia skin hydrolysate was the lowest. Grass carp skin hydrolysate was not able to form stable foam, unlike the Nile perch and Nile tilapia skin hydrolysate. Alcalase treated freshwater fish skin exhibited satisfactory functional properties hence may play an important role as an ingredient in the food and pharmaceutical industry.

Acute toxicity, behavioral changes, and histopathological effects of deltamethrin on tissues (gills, liver, brain, spleen, kidney, muscle, skin) of Nile tilapia (Oreochromis niloticus L.) fingerlings

Deltamethrin, a synthetic pyrethroid contaminating aquatic ecosystems as a potential toxic pollutant, was investigated in the present study for acute toxicity. The purpose of this study was to evaluate LC(50) values of deltamethrin on Nile tilapia (Oreochromis niloticus L.) fingerlings and investigate histopathological responses of fish exposed to deltamethrin. The 48 h LC(50) value for Nile tilapia fingerlings was estimated as 4.85 microg/L using static test system. In addition, behavioral changes at each deltamethrin concentration were observed closely. All fish, exposed to 5 microg/L deltamethrin revealed severe morphological alterations in the gills and liver. In the gills hyperemia, fusion of secondary lamellae and telangiectasis were observed; whereas hydropic degenerations in liver were observed in all examined fish. The results are significant for reporting acute deltamethrin toxicity in terms of behavioral and histopathological changes: Deltamethrin is highly toxic to fingerlings.

Avaliação da resistência da pele de tilápia do Nilo (Oreochrmis niloticus) nos sentidos longitudinal, transversal e diagonal, depois de submetida ao curtimento com sais de cromo e recurtimento com diferentes agentes curtentes

The objective of this experiment was to evaluate the resistance of the Nile tilapia (Oreochromis niloticus) skin in longitudinal, transversal and diagonal sections after tanning with chromium salts and re-tanning with different tanning substances. Skins were distributed in a totally randomized design, 3 by 3, with three re-tanning techniques (T1 = with 4% chromium salts; T2 = 6% vegetal tannins; T3 = with 6% synthetic tannins) coupled with three removal positions (P1 = longitudinal position; P2 = transversal position and P3 = diagonal position), with 6 replications per treatment in triplicate. Hide was considered the experimental unit. The EMIC dynamometer was used for traction, lengthening and progressive tearing resistance. Hide thickness ranged from 1.00 to 1.20 mm with no difference in re-tanning techniques. Although no significant difference in traction existed with regard to re-tanning techniques, there was a higher significant difference with regard to transversal position removal of proofs (11.92 N/mm2). Re-tanning technique and position did not affect progressive tearing, which ranged from 24.47 to 29.12 N/mm. Hide in the transversal position had greater elongation of technique, albeit no difference occurred in T2 technique for longitudinal position. Greater resistance to traction and elongation occurred in re-tanned hide with chromium salts, while re-tanning and position did not affect progressive tearing

Comparative study of iodothyronine outer ring and inner ring deiodinase activities in five teleostean fishes

The presence of outer ring deiodinating (ORD) and inner ring deiodinating (IRD) activities was investigated in different tissues of Oreochromis niloticus (Nile tilapia), Clarias gariepinus (African catfish), Oncorhynchus mykiss (rainbow trout) and halmus maximus (turbot). High-Km rT3 ORD is present in the kidney of most of the fishes studied, except in catfish. In turbot, besides the kidney, rT3 ORD is also present in liver, heart and ovary. Low-Km T4 ORD is found in the liver and low-Km T3 IR the brain of all the fishes studied. In addition, low levels of low-Km T3 IRD were demonstrated in gill and skin of Nile tilapia, liver of rainbow trout and gill and kidney of turbot. For the different teleosts, the biochemical properties of the different rT3-deiodinating enzymes mentioned, T4 ORD in liver and T3 IRD in brain and tilapia gill were compared to those of the deiodinases formerly characterized in Oreochromis aureus (blue tilapia). In general, the different deiodinases demonstrate analogous sensitivities to iodothyronines and inhibitors, although minor differences occur. The various deiodinating enzymes all depend on addition of dithiothreitol and demonstrate maximal activity pH between 6.5 and 7. The optimal incubation temperature of rT3 ORD and T4 ORD in tilapia and catfish is 37 °C, in trout and turbot it varies, depending on the tissue, between 25 ° and 37 °C. For the different T3 IRD activities the optimal temperature is 37 °C in warmwater as well as in coldwater species. The apparent Km values for rT3 ORD lay in the μM range, for T4 ORD and T3 IRD they lay in the nM range. Vmax values are usually higher in tilapia as compared to the other teleosts studied. Based on the similarities in susceptibility to inhibition by different iodothyronines and inhibitors and the agreement of the apparent Km values, we conclude that the deiodinating enzymes in teleosts are more similar to mammalian deiodinases than is generally accepted.