Study On Lipid Extraction And Comprehensive Utilization Of Residue From Nannochloropsis Sp.

China possesses a vast sea area,which has facilitated the cultivation and growth of aquaculture to a considerable extent.This,in turn,has provided favorable conditions for the cultivation of Nannochloropsis sp.Nannochloropsis sp.,which are abundant in lipids,proteins,polysaccharides,dietary fiber,pigments,and various trace elements,making them highly nutritious and promising for various applications.This study aimed to investigate the effects of different extraction methods and solvents on the lipid yield and eicosapentaenoic acid(EPA)content of Nannochloropsis sp.Furthermore,the correlation between lipid concomitants and antioxidant capacity was also explored.Additionally,insoluble dietary fiber and crude protein of algal residue were prepared by utilizing defatted microalgae residue.The structure of the microalgae residue insoluble dietary fiber was characterized,and the physicochemical properties of the microalgae residue insoluble dietary fiber as well as its in vitro hypoglycemic and lipid lowering functional properties were studied.The specific research content and results are as follows:(1)Optimization of lipid extraction process from Nannochloropsis sp.First,compare the effects of different extraction methods and solvents on lipid yield and EPA content of lipid from Nannochloropsis sp.It was found that when the extraction method was ultrasonic assisted solvent method and the extraction solvent was hexane-ethanol,the lipid yield and EPA content were both higher.Secondly,Combining with single factor experiment and response surface optimization experiments,the process of ultrasound-assisted hexane-ethanol extraction of lipid from Nannochloropsis sp.was optimized.The optimized process conditions obtained are: ultrasound temperature 50℃,ultrasound time 60 min,material liquid ratio 1:15,ultrasound power 240 W,and hexane ethanol ratio 1:2.5,Under these process conditions,the extraction yield of lipid from Nannochloropsis sp.was 24.05%± 0.08%,and the absolute EPA content was 10.92±0.22g/100 g lipid.(2)Comparison of lipid concomitants extracted from Nannochloropsis sp.with different solvents and their antioxidant propertiesCompare the physicochemical properties,lipid concomitant content,and lipid antioxidant properties of Nannochloropsis sp lipids extracted from different solvents.It was found that the ethanol group and the isopropanol group had higher acid values and peroxide values,and the ethanol group had the highest content of total phenols(4.80mg/g)and chlorophyll(3057.18 mg/100g),while the isopropanol group had the highest content of polyunsaturated fatty acids(especially EPA);The chloroform methanol group had a higher iodine value and the highest cholesterol content(21.52 mg/g);The n-hexane group had the highest content of total tocopherols(87.76 mg/100g);The petroleum ether group has the highest content of β-carotene(1119.70 mg/100g)and total carotenoids(1137.73 mg/100g).Different solvents have significant effects on the lipid concomitant content of Nannochloropsis sp.,which is related to its own polarity and its morphology and location in the cell.According to Pearson’s bivariate correlation analysis,this study observed that tocopherols and β-carotene played a major role in the antioxidant capacity of Nannochloropsis sp.lipids.(3)Study on the comprehensive utilization of residue from Nannochloropsis sp.First,Use defatted Nannochloropsis sp.residue as raw material to extract insoluble dietary fiber and algal residue protein through an ultrasound-assisted alkali method.The extraction process was optimized using comprehensive single-factor and orthogonal experiment.The optimized process conditions obtained are: NaOH concentration 1.8mol/L,ultrasonic extraction time 45 min,material liquid ratio 1:40,ultrasonic extraction temperature 55 ℃.Under these process conditions,the yield of algae residue insoluble dietary fiber was 24.98%,and the purity was 86.12%.Secondly,the structure,physicochemical properties,and adsorption performance of algal residue insoluble dietary fiber were characterized.It was found that algal residue insoluble dietary fiber had high water holding capacity(6.65 g/g),water swelling capacity(6.25 mL/g),and oil holding capacity(1.90 g/g),which was beneficial to improving its adsorption performance.Algae residue insoluble dietary fiber also showed good adsorption performance for nitrite ions,glucose,cholesterol,and sodium cholate.Finally,analyze and detecte the amino acid composition of algal residue protein.A total of 17 amino acids were detected in algal residue protein,and the total amount of amino acids reached 51.33g/100 g algal residue protein.The content of essential amino acids accounted for 42.16%of the total amino acids,1.77 times the recommended value of FAO/WHO.This study employed the ultrasound-assisted solvent method to extract Nannochloropsis sp.lipids and explored the correlation between lipid concomitants and the lipid antioxidant properties in Nannochloropsis sp.Additionally,this study investigated the comprehensive utilization of Nannochloropsis sp.residue after defatting,which not only provided a research foundation for the development of high-quality Nannochloropsis sp.lipids,but also broadened the research ideas for the comprehensive utilization of Nannochloropsis sp.