Lipid composition of the liver oil of the ray, Himantura bleekeri

Comparative oil extraction from mutt (Myliobatis goodei) liver by enzymatic hydrolysis: free versus immobilized biocatalyst

BACKGROUND

The development and fine-tuning of biotechnological processes for fish oil extraction constitute a very important focus to contribute to the development of a food industry based on fish consumption. This work lies in a comparative analysis of the oil extraction yield of Myliobatis goodei livers using free and immobilized enzymes.

RESULTS

An immobilized biocatalyst was designed from the cell-free extract of a Bacillus sp. Mcn4. A complete factorial design was used to study the components of the bacterial culture medium and select the condition with the highest titers of extracellular enzymatic activities. Wheat bran had a significant effect on the culture medium composition for enzymatic production. The immobilized biocatalyst was designed by covalent binding of the proteins present in the cocktail retaining a percentage of different types of enzymatic activities (Mult.Enz@MgFe2 O4 ). Among the biocatalyst used, Alcalase® 2.4 L and Purazyme® AS 60 L (free commercial proteases) showed extraction yields of 87.39% and 84.25%, respectively, while Mult.Enz@MgFe2 O4 achieved a better one of 89.97%. The oils obtained did not show significant differences in their physical-chemical properties while regarding the fatty acid content, the oil extracted with Purazyme® AS 60 L showed a comparatively lower proportion of polyunsaturated fatty acids.

CONCLUSIONS

Our results suggest that the use of by-products of M. goodei is a valid alternative and encourages the use of immobilized multienzyme biocatalysts for the treatment of complex substrates in the fishing industry. © 2023 Society of Chemical Industry.

The smooth-hound lipolytic system: Biochemical characterization of a purified digestive lipase, lipid profile and in vitro oil digestibility

In order to identify fish enzymes displaying novel biochemical properties, we choose the common smooth-hound (Mustelus mustelus) as a starting biological material to characterize the digestive lipid hydrolyzing enzyme. A smooth-hound digestive lipase (SmDL) was purified from a delipidated pancreatic powder. The SmDL molecular weight was around 50kDa. Specific activities of 2200 and 500U/mg were measured at pH 9 and 40°C using tributyrin and olive oil emulsion as substrates, respectively. Unlike known mammal pancreatic lipases, the SmDL was stable at 50°C and it retained 90% of its initial activity after 15min of incubation at 60°C. Interestingly, bile salts act as an activator of the SmDL. It's worth to notice that the SmDL was also salt-tolerant since it was active in the presence of high salt concentrations reaching 0.8M. Fatty acid (FA) analysis of oil from the smooth-hound viscera showed a dominance of unsaturated ones (UFAs). Interestingly, the major n-3 fatty acids were DHA and EPA with contents of 18.07% and 6.14%, respectively. In vitro digestibility model showed that the smooth hound oil was efficiently hydrolyzed by pancreatic lipases, which suggests the higher assimilation of fish oils by consumers.

Lipid content and fatty acid profile of Senegalese sole (Solea senegalensis Kaup, 1858) juveniles as affected by feed containing different amounts of plant protein sources

A growth trial with Senegalese Sole (Solea senegalensis Kaup, 1858) juveniles fed with diets containing increasing replacement levels of fishmeal by mixtures of plant protein sources was conducted over 12 weeks. Total fat contents of muscle, liver, viscera, skin, fins and head tissues were determined, as well as fatty acid profiles of muscle and liver (GC-FID analysis). Liver was the preferential local for fat deposition (5.5-10.8% of fat) followed by fins (3.4-6.7% fat). Increasing levels of plant protein in the diets seems to be related to increased levels of total lipids in the liver. Sole muscle is lean (2.4-4.0% fat), with total lipids being similar among treatments. Liver fatty acid profile varied significantly among treatments. Plant protein diets induced increased levels of C16:1 and C18:2 n-6 and a decrease in ARA and EPA levels. Muscle fatty acid profile also evidenced increasing levels of C18:2 n-6, while ARA and DHA remained similar among treatments. Substitution of fishmeal by plant protein is hence possible without major differences on the lipid content and fatty acid profile of the main edible portion of the fish - the muscle.

Lipid classes and fatty acid profile of selected Indian fresh water fishes

Lipid extracts from meat, head and viscera of Indian fresh water fishes, viz., catla, rohu, mrigal, common carp and tilapia were analyzed for lipid class distribution and fatty acid profile. The yield of meat ranged from 66.0-79.5% and total lipid content in meat was 0.8-3.8%. The total lipid content was higher (>4.0%) in head and viscera. Neutral lipids constituted 71.5-93.3% of the total lipid extract. Higher glycolipid content of 25.2% was observed in lipid extract from meat of common carp and higher phospholipid content (13.7%) was observed in lipid extract from meat of mrigal. Hydrocarbons, sterolesters and triacylglycerol were the major fractions of neutral lipids. Unsaturated fatty acids dominated in all the samples. Palmitic and oleic acids were the major fatty acids found in all the lipid extracts. Docosahexaenoic acid content was higher than 3% in lipid extract from meat of all the fishes. However, in most of the fishes, the content of eicosapentaenoic acid and docosahexaenoic acid were higher in visceral lipids.

Variation in fat content and fatty-acid composition of the Baltic herring Clupea harengus membras

The fat content and fatty-acid profiles of herring, Clupea harengus membras, from the southern Baltic Sea varied depending on when (fishing season) and where (fishing grounds) the fish were caught as well as on their size and sex. The fat, protein and dry matter content and the fatty-acid profiles were assayed in C. h. membras muscle tissue. The changes observed in fatty-acid profiles were determined by factors such as specimen mass and fat content, which, in turn, depended on fishing season. This is explained by dietary differences between juvenile and older fish. Gonad maturation and spawning in the latter are also factors. The study results provide confirmation of the hypothesis that polyunsaturated fatty acids (PUFA), in particular docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), play vital roles in the sexual maturation of C. h. membras.