Neutral Lipase Activity Research Articles

An Investigation of Volatile Flavor Compounds and Lipolysis-Oxidation in Coppa as Affected by the Inoculation of Coagulase-Negative Staphylococcus during the Air-Drying Stage.

This study aimed to explore the effects of coagulase-negative Staphylococcus inoculation on flavor generation and lipolysis-oxidation in Coppa. Acid lipase, neutral lipase, phospholipase, and lipoxygenase (LOX) activities, as well as free fatty acids, volatile compounds, and sensory evaluation, were determined during the fermentation and air-drying processes of Coppa over 40 days. Staphylococcus carnosus and Staphylococcus xylosus or a combination of both strains were selected for this study, and natural fermentation was treated as a control. The results showed that Staphylococcus inoculation significantly enhanced lipase and LOX activities, and mixed strains had a superior effect. Palmitic acid, stearic acid, linoleic acid, and oleic acid were identified as the predominant free fatty acids in Coppa, with the mixed fermentation group exhibiting the highest contents. Acids, aldehydes, alcohols, ketones, esters, and phenols were found for the volatile compounds in Coppa. These findings thus suggested a positive role of Staphylococcus inoculation in activating lipolysis-oxidation and contributing to the flavor formation of Coppa during the air-drying stage.

Effects of low salt on lipid oxidation and hydrolysis, fatty acids composition and volatiles flavor compounds of dry-cured ham during ripening

In order to study the effect of low salt on lipid oxidation and volatile flavor of dry-cured ham, a formula containing 18% potassium lactate, 12% lysine and 70% NaCl was used as an alternative salt for curing ham. The control group using 100% NaCl as pickled formulation dry-cured ham.The results showed that low salt significantly increased peroxide value (POV) and thiobarbituric acid value (TBARS) (P < 0.05). Acid lipase, neutral lipase, and phospholipase enzyme activity, as well as the amount of free fatty acids (FFAs), were all considerably higher in the low salt group than in the full salt group (P < 0.05). The volatile flavor compounds of dry-cured ham were determined by GC-MS, and 14 differential metabolites were screened out by using OPLS-DA analysis based on P < 0.05 and VIP >1. The enrichment analysis showed that low salt mainly affected low molecules fatty acids (palmitic acid, stearic acid, linoleic acid and myristic acid). Meanwhile, low salt treatment also influenced biosynthesis of unsaturated fatty acids, linoleic acid metabolism, fatty acid biosynthesis, fatty acid elongation and fatty acid degradation. This study demonstrates that low salt promotes the formation of ham flavor quality by affecting lipid oxidation and hydrolysis.

Metabolic changes and propensity for inflammation, fibrosis, and cancer in livers of mice lacking lysosomal acid lipase

Lysosomal acid lipase (LAL) is the sole lysosomal enzyme responsible for the degradation of cholesteryl esters and triacylglycerols at acidic pH. Impaired LAL activity leads to LAL deficiency (LAL-D), a severe and fatal disease characterized by ectopic lysosomal lipid accumulation. Reduced LAL activity also contributes to the development and progression of non-alcoholic fatty liver disease (NAFLD). To advance our understanding of LAL-related liver pathologies, we performed comprehensive proteomic profiling of livers from mice with systemic genetic loss of LAL (Lal−/−) and from mice with hepatocyte-specific LAL-D (hepLal−/−). Lal−/− mice exhibited drastic proteome alterations, including dysregulation of multiple proteins related to metabolism, inflammation, liver fibrosis, and cancer. Global loss of LAL activity impaired both acidic and neutral lipase activities and resulted in hepatic lipid accumulation, indicating a complete metabolic shift in Lal−/− livers. Hepatic inflammation and immune cell infiltration were evident, with numerous upregulated inflammation-related gene ontology biological process terms. In contrast, both young and mature hepLal−/− mice displayed only minor changes in the liver proteome, suggesting that loss of LAL solely in hepatocytes does not phenocopy metabolic alterations observed in mice globally lacking LAL. These findings provide valuable insights into the mechanisms underlying liver dysfunction in LAL-D and may help in understanding why decreased LAL activity contributes to NAFLD. Our study highlights the importance of LAL in maintaining liver homeostasis and demonstrates the drastic consequences of its global deficiency on the liver proteome and liver function.

Effect of sodium replacement on the quality characteristics of pastırma (a dry-cured meat product)

This study aims to investigate the effect of sodium replacement on the quality characteristics of pastırma. For this purpose, pastırma production with four different salt mixtures (I. 100 % NaCl; II. 50 % NaCl + 50 % KCl; III. 40 % NaCl + 40 % KCl + 20 % CaCl2; IV. 30 % NaCl + 40 % KCl + 20 % CaCl2 + 10 % MgCl2) were carried out using traditional method. The use of different salt mixtures for pastırma had no statistically significant effect on the microbial counts and residual nitrite of the final product. The a* and b* values were affected by this treatment. The salt mixture containing CaCl2 or CaCl2 + MgCl2 significantly decreased the pH values and sensory scores. The eighteen volatile compounds were affected by the salt mixtures. Na+, K+, Ca2+, and Mg2+ had a certain increase depending on their ratio in the salt mixtures. The highest Cathepsin activity in all pastırma samples was observed in Cathepsin B + L. The salt mixture with NaCl + KCl + CaCl2 + MgCl2 increased acid lipase activity. However, this mixture had no significant effect on neutral lipase activity.

Effects of the addition of exogenous lipase on lipolysis and lipid oxidation during wet‐curing and dry‐ripening of silver carp inoculated with mixed starter cultures

SummaryLipid degradation caused by lipolysis and oxidation plays an important role in the evolution of final product quality of cured silver carp. This study aimed to determine the impact of exogenous lipase (ExL) on lipolysis and lipid oxidation during the wet‐curing and dry‐ripening of silver carp inoculated with mixed starter cultures. The addition of ExL to silver carp increased the hydrolysis of total lipids and phospholipids. The free fatty acids (FFAs) content during wet‐curing was significantly higher in the ExL‐treated group compared with the control. Increased FFA accumulation contributed to a high level of conjugated dienes, peroxides and thiobarbituric acid‐reactive substances in the ExL‐treated group, indicating that the lipid oxidation was improved by the addition of ExL. Increased neutral lipase, acid lipase and phospholipase activities during the wet‐curing stage might explain the more extensive release of FFAs in the presence of ExL. The addition of ExL promotes the hydrolysis and oxidation of lipids in cured silver carp.

Hormone-sensitive lipase: sixty years later

Hormone-sensitive lipase (HSL) was initially characterized as the hormonally regulated neutral lipase activity responsible for the breakdown of triacylglycerols into fatty acids in adipose tissue. This review aims at providing up-to-date information on structural properties, regulation of expression, activity and function as well as therapeutic potential. The lipase is expressed as different isoforms produced from tissue-specific alternative promoters. All isoforms are composed of an N-terminal domain and a C-terminal catalytic domain within which a regulatory domain containing the phosphorylation sites is embedded. Some isoforms possess additional N-terminal regions. The catalytic domain shares similarities with bacteria, fungus and vascular plant proteins but not with other mammalian lipases. HSL singularity is provided by regulatory and N-terminal domains sharing no homology with other proteins. HSL has a broad substrate specificity compared to other neutral lipases. It hydrolyzes acylglycerols, cholesteryl and retinyl esters among other substrates. A novel role of HSL, independent of its enzymatic function, has recently been described in adipocytes. Clinical studies revealed dysregulations of HSL expression and activity in disorders, such as lipodystrophy, obesity, type 2 diabetes and cancer-associated cachexia. Development of specific inhibitors positions HSL as a pharmacological target for the treatment of metabolic complications.

Regulation of triglyceride metabolism in medaka (Oryzias latipes) hepatocytes by Neu3a sialidase.

Fish store triglycerides (TGs) in the liver, muscle, and adipose tissue and TGs constitute an energy source upon metabolic demand. The liver generally plays important roles in lipid metabolism. Recent studies have suggested the possibility of hepatic lipidmetabolic regulation by ganglioside in mammals; however, ganglioside-mediated regulation of lipid metabolism is unclear in fish. This study aimed to clarify the role of ganglioside in fish TG metabolism, with particular reference to Neu3a, a ganglioside-specific sialidase expressed in the fish liver. Under fasting conditions, there was a decrease in hepatic TG contents, and neu3a mRNA level was significantly up-regulated in the medaka liver. To determine the role of Neu3a in hepatic lipid metabolism, Neu3a stable transfectants were generated using fish liver Hepa-T1 cells. After treating Neu3a cells with oleic acid, reduction of TG was detected in comparison with the mock cells. Furthermore, lipase activity was greater in Neu3a cells than in mock cells. To examine which ganglioside regulates these events, alterations of ganglioside composition in Neu3a cells were analyzed. Neu3a cells exhibited increased level of lactosylceramide (LacCer), a Neu3 enzymatic product originating from GM3. In addition, exposure of LacCer toward Hepa-T1 cells resulted in an increase of neutral lipase activity. The present results suggest that Neu3a up-regulation in medaka under fasting condition accelerates hepatic TG degradation for energy production via GM3 desialylation.

Changes in Lipase and Antioxidant Enzyme Activities during Processing of Cantonese Sausage with D-Sodium Erythorbate

Pork was used as raw material to produce Cantonese sausage, with additions of 0.05% or 0.1% D-sodium erythorbate. The oxidation indices (peroxide value, TBARS value, carbonyl value, and conjugated dienes value) and enzyme activity (total phospholipase, acid lipase, neutral lipase, superoxide dismutase, and glutathione peroxidase) were measured in the sausages at different processing periods. The results showed slowed lipid oxidation in the presence of D-sodium erythorbate, inhibition of total phospholipase, acid lipase, and neutral lipase activities, and increased superoxide dismutase activity, with little change in glutathione peroxidase activities. When increasing D-sodium erythorbate, the superoxide dismutase activity was negatively correlated with the peroxide value at 5 h (P&lt;0.01), the neutral lipase activity was positively correlated with the conjugated dienes value at 15 h (P&lt;0.01), and the total phospholipase activity was positively correlated with the peroxide value at 30 h (P&lt;0.01). This study explored the antioxidant effect of D-sodium erythorbate and provides a theoretical foundation to improve the quality of Cantonese sausage.

Effects of high pressure treatment on lipolysis-oxidation and volatiles of marinated pork meat in soy sauce

To investigate the effect of high pressure (HP) treatment (150 and 300 MPa for 15 min at 20 °C) on lipolysis-oxidation and volatile profile of marinated pork meat in soy sauce, the changes of lipase, phospholipase and lipoxygenase (LOX) activities, TBARS, free fatty acids and volatiles composition in control and HP treated samples were analyzed. Acid and neutral lipase activities and free fatty acids content decreased, while LOX activity and TBARS increased after HP treatment. Phospholipase had well stability under HP. The levels of volatile compounds from lipid oxidation and brine increased under HP and then contributed 73.16–78.25% of the typical aroma, while volatile compounds from carbohydrate fermentation, especially acetic acid, decreased with the pressure increasing. The decrease of free fatty acids during pressurization was probably attributed to the decline of lipase activity and the increase of LOX activity. These findings indicated that HP (150–300 MPa/15 min) promoted lipid oxidation and the permeation of brine, but inhibited carbohydrate fermentation.

Activities of Endogenous Lipase and Lipolysis Oxidation of Low-Salt Lactic Acid-Fermented Fish (&lt;i&gt;Decapterus maruadsi&lt;/i&gt;)

There is increasing demand for low-salt meat products that retain traditional flavors. In this study, dry-salted fish (Decapterus maruadsi) were processed by 2 methods to obtain traditional salted fish (HS) and low-salt lactic acid-fermented fish (LAF). The relationship between lipolysis and lipid oxidation was investigated by evaluating changes in endogenous lipase (lipolytic enzymes; lipoxygenase, LOX), free fatty acid composition, thiobarbituric acid reactive substances (TBARS), and peroxide value (POV) during processing. Lipolytic enzyme activity showed a decreasing trend, in general. LOX activity initially increased and eventually decreased. Phospholipase, acid lipase, and neutral lipase activity was 0.33, 0.17, 0.57 (in HS) and 0.39, 0.25, 0.67 (in LAF) times in the final product than the activity levels observed in fresh fish. A principal component analysis indicated that phospholipase and neutral lipase play major roles in promoting lipid hydrolysis (in HS and LAF), the correlation between lipolytic activity and lipid oxidation in HS is greater than the correlation in LAF, and the contribution of LOX to lipid oxidation was minor in salted fish.

Effects of increasing protein level on the performance, enzyme activity and body composition of the Brazilian sardine, Sardinella brasiliensis (Steindachner, 1879)

A six-week growth trial was performed to estimate the dietary protein requirements for maximum growth of juvenile Brazilian sardine (Sardinella brasiliensis) based on growth performance, feed utilization, body composition and digestive enzyme activity. Six isoenergetic diets were formulated to contain protein levels that increased from 250 to 500 g/kg. Each diet was randomly assigned to triplicate groups of 160 fish with mean initial body weight of 0.93 ± 0.13 g, which were fed four times a day to apparent satiation. Growth tended to increase with the increase in the dietary protein level up to 400 g/kg. Total protein intake was indirectly correlated to apparent protein utilization. No significant differences in whole-body composition were found between fish fed the different protein levels. Acid protease and neutral lipase activities did not show significant differences among the different protein dietary groups. Alkaline protease activity increased in fish fed up to 350 g/kg of protein and amylase activity in fish fed up to 400 g/kg. Using polynomial regression, 367 g/kg was estimated to be the optimum dietary protein requirement for maximum weight gain of juvenile Brazilian sardines.

Incorporation of pig back fat in restructured dry cured ham to facilitate the release of unsaturated fatty acids and generation of volatile compounds

The aim of the present study was to evaluate the effects of incorporating pig back fat in restructured dry cured ham (RDH) on its free fatty acid profile (FFA) and the volatile compounds released. Fresh raw hams were skinned, boned, and cut into meat cubes (4–6 × 4–6 × 4–6 cm). The meat cubes were restructured with 0, 2, and 4% pig back fat paste into raw restructured ham. After 30 days of ripening, the FFA and volatiles in the RDH were identified using gas chromatography and gas chromatography mass spectrometry, respectively. The results showed that exogenous pig back fat incorporation from 2 to 4% gave rise to increased neutral lipase activity (p &lt; 0.05) and to enhanced lipid degradation and unsaturated fatty acid release in the RDH sample. A total of 63 volatile compounds were isolated from RDH. The most abundant volatiles were alcohols, followed by esters and aldehydes. The chromatographic areas of the total volatile amount, short chain esters, 3‐hydroxy‐2‐butanone, 2‐nonanone, long chain hydrocarbons, and pyrazines increased with pig back fat incorporation, suggesting that exogenous pig back fat incorporation could improve the sensorial quality of restructured dry cured ham.Practical application: Hams produced from genotypes with high intramuscular fat have more intense and persistent aroma, because intramuscular triacylglycerols are a good trap for most aroma compounds and also a source of volatile (aromatic) compounds. Nowadays, mixed diet feed systems or other specific feeding strategies could improve the fat content and composition of raw ham, but led to lower nutritional and sensory quality of hams. Perhaps, the major problem for the relatively poor quality of dry cured ham may be the leanness of modern genotypes, and the pigs from these genotypes are not suitable for dry cured ham production. Thus, thinking from another perspective, through incorporating exogenous pig back fat directly into raw ham, the present work have successfully improved the sensorial properties of dry cured hams.Restructured dry cured hams (RDH) with different pig back fat levels were successfully manufactured. This work shown that large differences in the free unsaturated fatty acid and volatile compounds of RDH can be caused by the exogenous pig back fat incorporation. An increase in pig back fat level from 2 to 4% in RDH significantly enhanced the release of unsaturated fatty acid, and facilitated the generation of volatile compounds including esters, ketones, aliphatic hydrocarbons, and aromatic hydrocarbons.

Incorporation of pig back fat in restructured dry cured ham to enhance the lipase and lipoxygenase activities

The aim of the present study was to evaluate the effect of incorporating pig back fat in restructured dry cured ham (RDH) on the lipase and lipoxygenase activities. Fresh raw hams were skinned, boned, cut into meat cubes (4–6 × 4–6 × 4–6 cm). The meat cubes were restructured respectively with 0, 2, and 4% pig back fat paste into raw restructured ham. After 30 days of ripening, lipase activity in RDH was determined using a fluorescence spectrometer (λex = 350 nm, λem = 445 nm), the result was expressed as µmol of released 4‐methylumbelliferone per hour per gram protein. Lipoxygenase (LOX) activity in RDH was assayed in a 96‐Well Plate Reader M200, one unit of LOX activity was defined as an absorbance increment per minute per milligram protein at 234 nm. Results showed that exogenous pig back fat incorporation from 2 to 4% gave rise to the increased neutral lipase and LOX activities (p &lt; 0.05), and the enhanced hydrolysis of neutral lipids and phospholipids, and production of free fatty acids, suggesting that exogenous pig back fat incorporation could improve the quality of RDH.Practical applications: Hams produced from genotypes with high intramuscular fat have more intense and persistent aroma, because intramuscular triacylglycerols are a good trap for most aroma compounds. However, traditional extensive feeding regime give rise to massive consumption of natural resource and this strategy is not always feasible because availability of natural resource is largely influenced by environment. The present work has provided a successful strategy to improve dry cured hams’ quality that incorporating exogenous pig back fat directly into raw ham from general confinement feeding, not through traditional extensive feeding, could increase the content of lipid, and enhance the neutral lipase and LOX activities in dry cured meat.Restructured dry cured hams (RDH) with different pig back fat levels were successfully manufactured. This work shown that large differences in the neutral lipase and LOX (Lipoxygenase) activities of RDH can be caused by the exogenous pig back fat incorporation. An increase in pig back fat level from 2 to 4% in RDH significantly enhanced the neutral lipase and LOX activities during ripening.

Effects of increasing the dietary lipid levels on the growth performance, body composition and digestive enzyme activities of the teleost pejerrey (Odontesthes bonariensis)

The present study aimed at determining the growth performance, body composition and digestive enzyme activities of pejerrey (Odontesthes bonariensis) juveniles fed with graded levels of dietary lipids: 6% (L6), 10% (L10) and 25% (L25). Following a 14-week growth trial, weight increase decreased in group L6. The protein productive value increased in groups L10 and L25, whereas group L10 showed the highest lipid productive value. Hepatosomatic and mesenteric fat indexes decreased in group L6. Body protein content decreased with the increase in dietary lipids (L6>L10>L25); whereas body lipid content, and nitrogen and energy retentions were the lowest in group L6. The muscle fatty acid composition was differentially regulated by the diets except EPA, DHA and n-3 PUFA contents. The total n-6 PUFA decreased in group L6. The n-3 PUFA tended to accumulate in the muscle of the fish; group L10 exhibiting the lowest accumulation rate. The total activity of neutral lipase was stimulated in group L25 whereas the specific activity of pancreatic lipase decreased in this same group. While group L6 showed the lowest total activity of alkaline proteases, group L10 showed the highest total activity of trypsin. A decrease in the specific activity of amylase in group L25 followed the decrease in dietary starch. In summary, 25% of dietary lipids did not have additional stimulatory effects on the digestive proteases activity compared to 10%, but negatively affected pancreatic lipase and trypsin activities. Moreover, the decrease of the latter in group L25 suggests that approximately 10% of dietary lipids might support the growth of pejerrey juveniles reared in captivity.

Digestion of lipids and carbohydrates from microalgae (Chaetoceros muelleri Lemmermann and Isochrysis aff. galbana clone T-ISO) in juvenile scallops (Pecten maximus L.)

The digestion of laminaran and neutral lipids from the microalgae Chaetoceros muelleri or mixtures of C. muelleri and Isochrysis galbana clone T-ISO in 4-mm scallops Pecten maximus were studied. The microalgae were cultivated at fixed low and high growth rate (5% and 60% of μmax). The cultivation method clearly affected the lipid and carbohydrate contents, as well as their enzyme activity. Chaetoceros muelleri and T-ISO grown at low growth rate exhibited a considerably higher content of lipids and carbohydrates than those algae grown at high growth rate. The specific activity of laminaranase and neutral lipase was the highest in C. muelleri grown at the low growth rate. Growth rate of scallops was best when they were fed a mono-species diet of C. muelleri grown at low growth rate. The growth rate of the scallops was positively correlated to the dietary carbohydrate content as well as to the specific activity of neutral lipase and laminaranase in the diet. The capacity to digest carbohydrates (laminaran) might be limiting for the young scallops, and the content of carbohydrates and enzymatic activities of laminaran in the diet should be considered when formulating an optimal diet, both when the diet consist of live microalgae and formulated diets.

Characterization and expression of digestive neutral lipases during ontogeny of Atlantic cod ( Gadus morhua)

The major neutral lipase excreted by the pancreas in fish, is bile activated lipase (BAL). Here we present evidence that cod have a functional BAL and a non-functional pancreatic lipase related protein (PLRP). The Atlantic cod genome does not seem to contain colipase which is essential for pancreatic lipase activity. During the larval stages, the gene expression of BAL was low until the point when pyloric caeca started to differentiate and develop (~ 20 mm standard length (SL)). Then the expression increased until ~ 50 mm SL. The PLRP gene was expressed but showed very little regulation. The activity of neutral lipase did not increase in parallel to gene expression. The mismatch between activity and gene expression measurements may be partly explained by the unspecific analytical method, when analysing lipase activity in larva whole body. There is neutral lipase activity in numerous tissues in the fish larvae and the lipase activity in the gut, relatively to activity in the whole body, decreased with age. Furthermore, neutral lipase activity in rotifers was ten times higher than in whole cod larvae with full guts. Activity originating from the live prey may therefore explain the high whole body lipase activity from 3 to 20 dph. The results also indicate that “adult type” digestion of neutral lipid develops late in the larval period (from 20 mm SL), while other mechanisms of lipid uptake are active at the early larval stage.

Effect of prefreezing hams on endogenous enzyme activity during the processing of Iberian dry-cured hams

The use of frozen/thawed raw material in the processing of Iberian dry-cured ham has been studied to determine its effect on the sensory quality of the final product. The proteolysis and lipolysis processes were measured by the proteolytic and lipolytic enzyme activities and free amino acids and free fatty acids. The thawed Iberian hams had lower salt contents throughout the process. The use of thawing raw material did not affect the proteolytic enzymes, cathepsins, aminopeptidases and dipeptidylpeptidases, only the activity of dipeptidylpeptidase III was reduced due to thawing. Moreover, there were no differences in the content of free amino acids between fresh and thawed hams during the whole process. However, the use of thawing hams affected the lipolytic activity. The activity of phospholipase and neutral lipase were significantly higher in the thawed hams and also the content of free fatty acids, at all the stages analyzed. Consumer sensory analysis showed thawed Iberian hams had the lowest hardness, probably due to an intense proteolysis. The acceptability of the Iberian hams was similar between fresh and thawed hams.

Physical activity-induced alterations on tissue lipid composition and lipid metabolism in fattening pigs

In a first experiment one group of pigs was maintained in free-range conditions according to the traditional way in a Mediterranean forest (exercised-1) and another group was housed individually and received acorns (sedentary-1). In a second experiment two groups of pigs were fed a mixed diet for the whole experimental period. One of these groups was housed individually in 8 m 2 pens (sedentary-2). The other group was housed in a corridor and forced to walk daily (exercised-2). The subcutaneous fat and neutral lipids of muscle from the exercised pigs fed acorns had higher C18:1 n-9, MUFA, C18:1/C18:0, MUFA/SAT and lower C16:0 and SAT when compared with the fat from the pigs fed acorns in confinement. Those exercised animals fed the mixed diet had also lower C16:0 and SAT in subcutaneous fat and lower SAT and higher C18:2, C18:3, PUFA and MUFA/SAT in neutral lipids when compared with the sedentary pigs, which may indicate that delta-9-desaturase activity was higher in exercised than in sedentary pigs. Exercised pigs had higher acid and neutral esterases and lower neutral lipase activity than sedentary pigs. No differences in the α-tocopherol concentration and TBARS values of meat samples among the pigs that received a mixed diet either exercised or sedentary were observed. The moderate exercise reduced the postprandrial concentrations of triglycerides in plasma, but did not reduce other plasma levels.

Phospholipids vs. neutral lipids: Effects on digestive enzymes in Atlantic cod (Gadus morhua) larvae

The aim of this study was to evaluate the effect of dietary lipid classes (phospholipid vs. neutral lipid) and level of n-3 highly unsaturated fatty acids (HUFAs) on growth, survival and digestive enzymatic activity in Atlantic cod (Gadus morhua) larvae. Larvae were fed enriched rotifers from mouth opening and were weaned to formulated diets during a co-feeding period lasting from 17 days post hatch (dph) to 24 dph. Larvae were fed exclusively compound diets from 24 dph until the end of the experiment. Three isoproteic and isolipidic compound diets with gradually decreasing levels of DHA and EPA in the dietary phospholipid fraction (diet PL3>PL1>NL1) and increasing levels of total dietary neutral lipids (PL3<PL1<NL1) were used. Larvae fed the PL3 or PL1 had a significant higher dry weight than larvae fed the NL1 diet at the end of the experiment (45 dph). Survival did not differ significantly between treatments. A gut maturation index based on the relation between the amount of the brush border enzyme alkaline phosphatase and the cytosolic enzyme leucine-alanine aminopeptidase showed that the enterocyte maturation on 35 and 45 dph was better in larvae fed the PL3 and PL1 diet than larvae fed the NL1 diet. Dietary composition did not significantly affect the activity of α-amylase, but an age specific decrease in activity was observed. The dietary composition did affect the specific activity of trypsin, although showing variation in pattern between different larval ages at sampling. The activity of neutral lipase showed high variability between dietary treatments, but at the end of the experiment the specific activity of neutral lipase was positively connected to the dietary neutral lipid levels. The results from this study showed that cod larvae use DHA and EPA in the phospholipid fraction more efficiently compared to those in the neutral lipid fraction.

Neutral lipase and phospholipase activities in scallop juveniles (Pecten maximus) and dietary algae

Activities of the digestive enzymes neutral lipase and phospholipase A2 were present in 2-mm scallop juveniles, indicating an endogenous ability to digest lipids. When determined in the dietary microalgae, lipolytic activities of both enzymes differed significantly, being highest in Isochrysis galbana and Tetraselmis sp. and lowest in Chaetoceros mülleri. Compared with the activities found in scallop juveniles, enzyme activities from the microalgae were rather low and did not seem to contribute considerably to their digestive process. However, ingested algae seemed to have a regulating effect on the phospholipase activity in scallops, as juveniles fed I. galbana had a significantly lower activity than juveniles of the other treatments. No such effect was evident for neutral lipase, indicating different regulation mechanisms for both enzymes. Dietary effects on digestive enzymes in scallop juveniles should be considered when choosing new potential algal species as feed or for future formulation of artificial diets.