Extraction Of Protein And Nucleic Acid From Waste Brewer's Yeast With The Aid Of Physical Fields

In this paper 5 methods were applied for extracting protein and nucleic acid from brewer's yeast cells, they were pulsed electric fields (PEF) , ultrasound, autolysis, and two new methods, one was composed of PEF and autolysis treatment, and the other is combination treatment of PEF and autolysis technology. Comparative study of these five methods was carried out to find a method with distinct advantages, such as high extraction of protein and nucleic acid, no pollution for the environment and easily set-up to an industrial process.Firstly, pretreatment process of waste brwer's yeast was to prevent solution hetergenate caused by yeast cell sedimentation. The results showed that when yeast cell suspenting in water (25℃, pH6.5), cell flooculation reduced, and solution homogenate greatly raised.Base on pretreatment above, the efficency of aforementioned 5 methods on the extraction of protein and nucleic acid from brewer's yeast cells were investigated. The data demonstrated that each extraction mothod had significant effect on extraction of protein and nucleic acid, especially the new mild method of combination treatment of PEF and autolysis technology. Synergistic effects of PEF (2μs, 30.00kV/cm, 667pps, 0.15s/m, 720μs) and autolysis treatment (30g/LNaCl, 50℃, pH6.5, 6h) achieved the greasted extraction of protein and nucleic acid, which were 77.59 and 88.19% , respectively.Scanning electron microscope (SEM) showed that yeast cell treated by combined technologies of PEF and autolysis can remain integrity, and the cell wall nearly remained intact. The mechanical strength of the yeast cell wall decreased with the removal of the proteins, which caused the yeast cell walls crimple and easy to be disrupted.An industry process about extraction of protein and nucleic acid was established:one gram brewer's yeast was suspended in ten milliliter water, treatment of PEF and autolysis, then stirred (400r/min, Intermittent stirring) for accelerating intracelluar substances released from waste brewer's yeast. Then the process was followed by ultrafiltration with MWCO 500Da membrane, and separation of protein and nucleic acid with isoelectricfocus at pH4.2 and pH2.5 and desalination with MWCO 500Da dialysis membrane. Finally, protein and nucleic acid products were prepared by spray desiccation.