A new epoxy-based polymerizing/compositing synchronic process was carried out in 3D structure of a melamine sponge. The cured polymer formed a porous and wave-shaped coating on the surface of skeleton in a uniform way. The obtained composite sponge was used as a microflow support for the immobilization of phospholipase A 1 (PLA 1 , from Thermomyces lanuginosus/Fusarium oxysporum ) by co-adsorption/cross-linking with polyethylenimine (PEI). The loading amount and the specific activity of immobilized PLA 1 under the optimal immobilization conditions were 45.7 mg/g support and 9.1 U/mg protein . The PLA 1 -immobilized microflow supports were placed in a columnar reactor, in which transesterification was operated in continuous circulation way. The reaction produced DHA/EPA-incorporated phosphatidylcholine , the hydrolysis side reaction could be inhibited by removal of free water in the reaction medium. Under optimized conditions the incorporation percentage of DHA/EPA and PC yield of 54.3% and 82.4% within 18 h at 55 ℃, respectively. After 10 cycles, the immobilized PLA 1 retained 71.2% of the original activity. The use of microflow support has an advantage on easier scaling up the reactor size towards much larger productivity and higher efficiency.
Novel nano-composites were prepared by coating epoxy resin-based cationic polymer in nano-thickness via in-situ curing on the wall of macroporous SiO 2 with pore size of 0.5∼1 μm. By changing the thickness of polymer coating the porosity and specific surface area varied in range of 90.4∼83.9 % and 115∼74 m 2 /g, respectively. Through electrostatic adsorption phospholipase A 1 (PLA 1 ) was efficiently immobilized on the nano-composited support, the loading amount of PLA 1 on the nano-composited support reached to a maximum of 138.6 mg/g support , the specific activity of the immobilized PLA 1 reached as high as 21,300 U/g protein . The immobilized PLA 1 was applied for the highly efficient synthesis of DHA/EPA-rich phosphatidylcholine . The incorporation of DHA/EPA reached as high as 74.8 % and the yield of phosphatidylcholine (PC) was 83.1 % within 20 h at 60 °C using PC/ethyl esters mass ratio of 1:6. After 12 cycling reuses the immobilized PLA 1 still retained 57.8 % of the incorporation of DHA/EPA.
Fish oil is beneficial to health and its quality is significantly impacted by the extraction method. To determine the effect of various methods used to extract the oil on its chemical composition and thermal properties, tilapia oil extracted by dilute alkali hydrolysis, enzymatic hydrolysis, and microwave-assisted methods were investigated in this study. Nutrient analyses showed that freeze-dried tilapia contained fat (36.69 g/100 g freeze-dried tilapia), protein (49.95 g/100 g freeze-dried tilapia), ash (12.04 g/100 g freeze-dried tilapia) and moisture (1.21 g/100 g freeze-dried tilapia). Chemical analysis showed that the fish oil extracted by dilute alkali hydrolysis had the lowest acid value (AV) and peroxide value (POV) (AV: 0.77 mg KOH/g oil and POV: 3.76 mmol/kg oil) compared to the oil extracted using the other methods. The main fatty acid components were palmitic acid (22.78–23.16%), oleic acid (25.73–26.19%), and linoleic acid (15.69–15.98%). Furthermore, the oil extracted by dilute alkali hydrolysis showed significantly higher content of DHA+ EPA (2.30%). The thermal behaviors indicated that the aforementioned oils had significantly different crystal structures. The main endothermic peaks of fish oil extracted by dilute alkali hydrolysis, enzymatic hydrolysis and microwave-assisted methods were located at −2.03℃, −3.20℃ and −4.37℃, respectively. However, infrared spectroscopic analyses indicated them had the same characteristic functional groups. Consequently, different extraction methods significantly affect the oil’s physical and chemical properties without affecting spectral characteristics. Furthermore, these results advocated the use of alkali hydrolysis for fish oil extraction.
It has been reported that dietary n-3 polyunsaturated fatty acids (n-3 PUFAs) exert therapeutic potential for the preservation of functional β-cell mass. However, the effect of dietary n-3 PUFA deficiency on pancreatic injury and whether the supplementation of n-3 PUFA could prevent the development of pancreatic injury are still not clear. In the present study, an n-3 PUFA deficiency mouse model was established by feeding them with n-3 PUFA deficiency diets for 30 days. Results showed that n-3 PUFA deficiency aggravated streptozotocin (STZ)-induced pancreas injury by reducing the insulin level by 18.21% and the HOMA β-cell indices by 31.13% and the area of islet by 52.58% compared with the STZ group. Moreover, pre-intervention with DHA and EPA for 15 days could alleviate STZ-induced pancreas damage by increasing the insulin level by 55.26% and 44.33%, the HOMA β-cell indices by 118.81% and 157.26% and reversed the area of islet by 196.75% and 205.57% compared to the n-3 Def group, and the effects were significant compared to γ-linolenic acid (GLA) and alpha-linolenic acid (ALA) treatment. The possible underlying mechanisms indicated that EPA and DHA significantly reduced the ration of n-6 PUFA to n-3 PUFA and then inhibited oxidative stress, inflammation and islet β-cell apoptosis levels in pancreas tissue. The results might provide insights into the prevention and alleviation of pancreas injury by dietary intervention with PUFAs and provide a theoretical basis for their application in functional foods.Keywords:streptozotocin;polyunsaturated fatty acid;pancreas injury;oxidative stress;inflammation;apoptosis;mouse
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