Study On Extraction Method Of Crude Protein From Heterotrophic Chlorella

Chlorella is an excellent single cell protein source whose utilization rate and biological value are relatively high.Chlorella contains more than 20 kinds of amino acid,which include 8 kinds essential amino acid for adults and 9 kinds essential amino acid for infants.Chlorella has a complete variety and perfect proportion of amino acid.The protein of chlorella is highly utilized after digested and absorbed.It has been listed as the 21 st century human health food by FAO.In this experiment,Chlorella protothecoides was used as raw material for protein extraction.As the main oil-producing chlorella,the content of the high value-added product protein is about 12.2%,which can be used as a source of protein.Effective extraction and utilization of protein could balance the high cost of microalgae energy industry.The test results are as follows:1.Cell fragmentation: The hot alkali method was used to break chlorella cell after comparing tests.With the protein dissolution rate as an index,single factor tests were used to determine the best level of main factors in the extraction process,and then the interaction of main factors was studied by orthogonal test.The results showed that,the addition of NaOH was 20%,the solid-liquid ratio was 50:1,the fragmentation time was 60 min,and the fragmentation temperature was 55 ?,under these conditions,the protein dissolution rate of heterotrophic chlorella was the highest,55.24%.2.Protein crude extraction: The ammonium sulfate salting-out method was used to crude the protein of heterotrophic chlorella after comparing tests.With the protein precipitatio rate as an index,main factors affecting the protein precipitation rate,such as ammonium sulfate saturation,pH,temperature and time,were tested by single factor tests.On this basis,the response surface optimization test of three factors and three levels was carried out.The optimum protein crude extraction conditions were obtained: the ammonium sulfate saturation was 62%,the pH was 5.1 and the time was 30 min,under these conditions,the precipitation rate of heterotrophic chlorella protein was 92.14%.3.Cost analysis: We used the optimized medium to culture the heterotrophic chlorella and obtained 50 L culture medium at the end.The dry weight of algae cell was97.3 g/L,the protein content was 27.1%,and the oil content was 41.2%.The comparative tests of protein extraction were carried out between original culture medium and five times diluted culture medium.It was found that the cost-effective ratio of protein extraction directly from the original culture medium was higher.The yield of protein and oil was59.36% and 15.2% respectively.Therefore,theoretically,if 50 L medium was all used to extract protein and oil,we will get 782.6 g crude protein and 304.7 g oil.On this basis,the main cost calculation shows that the total cost of reagent needed is 847 yuan.Analyze and discuss about main cost can provide reference for the follow-up study to improve efficiency and reduce cost.