Concentration of docosahexaenoic acid in glyceride by hydrolysis of fish oil withcandida cylindracea lipase

In an attempt to concentrate the content of DHA (docosahexaenoic acid) in a glyceride mixture containing triglyceride, diglyceride and monoglyceride, fish oil was hydrolyzed with six kinds of microbial lipase. After the hydrolysis, free fatty acid was removed and fatty acid components of the glyceride mixtures were analyzed. When the hydrolysis withCandida cylindracea lipase was 70% complete, the DHA content in the glyceride mixture was three times more than that in the original fish oil. The EPA (eicosapentaenoic acid) content became almost 70% of the original fish oil. Hydrolysis with other lipases did not result in an increase in the DHA content in the glyceride mixtures. Hydrolysis of DHA-rich tuna oil (DHA content is about 25%) withCandida cylindracea lipase resulted in 53% DHA in the glyceride mixture. The EPA content, however, remained close to that of the original tuna oil. In this report, the acyl chain specificity of lipases is evaluated in terms of hydrolysis resistant value (HRV). HRV is the ratio between the DHA contents in the glyceride mixture of hydrolyzed oil and original oil. HRV clearly indicates differences in hydrolysis between DHA and other fatty acids (e.g., saturated and monoenoic acids).     

DHA油脂在精炼过程中氧化稳定性的变化

分析了DHA毛油依次经历脱胶、碱炼、脱色、脱臭等环节后,油脂的微组成及氧化稳定性变化。结果显示,在整个精炼过程中各微组分的含量整体呈下降趋势。DHA油脂对光稳定性:精油>脱色油>毛油/脱胶>碱炼油;DHA油脂对热稳定性(Rancimat法):脱色油>精油>脱胶油>毛油>碱炼油。DHA油脂在脱色环节之前,氧化稳定性差归因于其中促进氧化的微组分过多。在脱色环节之后油脂对热稳定性变差,归因于内源性的抗氧化组分在脱臭环节中大量损失。      

化学添加剂对裂壶藻突变株发酵产DHA的影响

为了研究外源化学添加剂对裂壶藻（Schizochytrium limacinum）突变株发酵合成脂肪酸（SFAs、PUFAs和DHA）的影响,采用基于气相色谱-质谱（GC-MS）联用技术分析裂壶藻突变株产油脂肪酸的组成。通过单因素和正交实验设计,优化了乙醇胺（ETA）、萘氧乙酸（BNOA）和水杨酸（SA）三种化学添加剂的最佳添加条件。结果表明,添加150 mg/L的乙醇胺（ETA）、10 mg/L萘氧乙酸（BNOA）和1 mg/L水杨酸（SA）,裂壶藻突变株的DHA产量最高,达到6.18 g/L,比对照组提高了12.77%。综上所述,添加适量的化学添加剂可以提高裂壶藻突变株DHA的含量。      

微生物发酵法生产EPA及DHA的研究进展

EPA和DHA是两种人体必需多不饱和脂肪酸,对人体健康有重要意义,微生物发酵法生产EPA和DHA具有稳定性好、易于分离纯化和工业化等优点,是近年来研究的热点。从微生物利用葡萄糖合成多不饱和脂肪酸的代谢途径和影响微生物合成多不饱和脂肪酸的因素出发,论述了微生物发酵法生产EPA和DHA的研究现状和最新进展。     

The methionine precursor dl-2-hydroxy-(4-methylthio)butanoic acid protects intestinal epithelial barrier function

dl-2-hydroxy-(4-methylthio)butanoic acid (HMTBA) is a source of dietary methionine (Met) that is widely used in poultry nutrition. We have previously shown that HMTBA is preferentially diverted to the transsulfuration pathway, which gives antioxidant metabolites such as taurine and glutathione. Therefore, here we hypothesize that this Met source can protect epithelial barrier function in an in vitro model of intestinal inflammation of Caco-2 cells. The results show that HMTBA prevents the increase in paracellular permeability induced by H₂O₂ or tumour necrosis factor-α. This effect can be attributed to the increased production of taurine and reduced glutathione. Similar results were obtained for dl-Met, although the protective role of the amino acid was less pronounced than that of the hydroxy analogue. In conclusion, the diversion to the transsulfuration pathway means that this Met precursor is of greater value than previously thought, due to its capacity to improve intestinal homeostasis and the quality of poultry products destined for human consumption.     

Mercury and Fatty Acids in Canned Tuna, Salmon, and Mackerel

ABSTRACT: Canned tuna ( n = 240), salmon ( n = 16), and mackerel ( n = 16) were analyzed for mercury and fatty acids. Average mercury levels were 188, 45, and 55 ppb, respectively, and below the FDA Action Level of 1000 ppb. "Light tuna in water" contained lower mercury (x = 54 ppb) compared with "white/albacore tuna in water," which contained higher eicosapentaenoic acid/docosahexaenoic acid (EPA/DHA) x= 711 mg/100 g wet tissue). Mercury residues in salmon (x = 45 ppb) and mackerel (x = 55 ppb) were lower than in tuna products, but the EPA/DHA levels were higher (salmon, ×= 1623 mg/100 g wet tissue; mackerel, ×= 851 mg/100 g wet tissue). Information from this study will help women of childbearing age to limit their intake of mercury while obtaining healthy fats from fish.     

Heterotrophic growth and nutritional aspects of the diatom Cyclotella cryptica (Bacillariophyceae): Effect of some environmental factors

To investigate the nutritional value of the diatom Cyclotella cryptica (Reimann, Lewin, and Guillard) as an alternative feed for use in the aquaculture industry, the heterotrophic growth characteristics and resultant fatty acid profile of the microalga were studied when cultivated under a variety of controlled salinity and temperature conditions. In addition, the effects of pH on the growth characteristics were also studied. The maximum specific growth rate was affected by initial pH and cultivation temperature, but not by salinity. The optimal pH and temperature ranges for growth were 7.2 to 8.1 and 22.5 to 25.0 °C, respectively. Lipid accumulation and the fatty acid composition were also affected by cultivation temperature and salinity. The optimal temperature range and salinity level for lipid accumulation were 18.0 to 25.0 °C and 11.2 psu, respectively. In all cases the fatty acid distribution was similar, with the most abundant fatty acids being palmitic acid (16:0), palmitoleic acid (16:1 n-7), stearidonic acid (18:4 n-3, SDA), eicosapentaenoic acid (20:5 n-3, EPA), and decosahexaenoic acid (22:6 n-3, DHA).     

Changes in lipids and their contribution to the taste of migaki-nishin (dried herring fillet) during drying

This study was conducted to investigate the changes in lipids and their effect on the taste of migaki-nishin during drying. Lipid was extracted from herring fillets following different drying stages to measure the degree of lipid oxidation and changes in lipid composition, and fatty acid profile. Peroxide value, carbonyl value and acid value of the lipids were significantly increased (P < 0.05) during the drying period. Marked increase in free fatty acids, with decreases in triglyceride and phospholipid content were observed in proportion to drying time and this result suggested that hydrolysis was induced by lipases and phospholipases. The decreases in polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were observed in the total lipids and phospholipid fraction. In addition, significant increase in PUFAs especially DHA was found in the free fatty acid fraction. Sensory evaluation showed that an addition of DHA to mentsuyu significantly (P < 0.05) enhances the intensities of thickness, mouthfulness and continuity. These results suggest that during drying period lipid oxidation was not only occurred but also lipolysis predominantly released DHA, which might have a contribution to kokumi enhancement of migaki-nishin.     

高DHA含量营养保健鸡蛋的研究

本文通过对产蛋鸡的日粮中添加不同DHA、α-亚麻酸组成和含量的强化多不饱和脂肪酸的饲料,考察了对鸡蛋蛋黄、鸡肉、鸡肝及鸡心中多不饱和脂肪酸组成和含量的影响,同时研究了不同饲料配方对产蛋鸡体重、产蛋率及采食量的影响。结果表明:对产蛋鸡喂养强化多不饱和脂肪酸的饲料15d后,鸡蛋蛋黄、鸡肉、鸡肝及鸡心中DHA、α-亚麻酸的含量达到稳定,而且强化饲料对产蛋鸡的体重、产蛋率及采食量无不良影响。     

Fatty acid profiles and fat contents of commercially important seawater and freshwater fish species of Turkey: A comparative study

The fat content and fatty acid compositions of edible muscle of commercially important seawater and freshwater fish species were investigated. The fatty acid compositions of seawater fish species were found to be 25.5–39.4% saturated (SFA), 13.2–29.0% monounsaturated (MUFAs) and 25.2–48.2% polyunsaturated acids (PUFAs), whereas the fatty acid compositions of freshwater fish from Lake Seyhan consisted of 28.0–34.6% saturated (SFA), 10.7–22.7% monounsaturated (MUFAs) and 23.2–43.7% polyunsaturated acids (PUFAs). The proportions of n3 PUFAs of seawater fish (ranging from 22.6 for waker to 44.2% for blue fish) were higher than those of n3 PUFAs of freshwater fish (ranging from 11.5% for North African catfish to 28.4% for zander). However, the levels of n6 PUFAs of seawater fish (ranging from 0.43% for blue fish to 14.4% for sea bass) were lower than those of n6 PUFAs of freshwater fish (ranging from 5.27% for kutum to 16.8% for tench). The results showed that fatty acid profiles of most freshwater fish are basically comparable to those of seawater fish as sources of PUFAs.