Dissertation
Dissertation > Environmental science, safety science > Processing and comprehensive utilization of waste > Light industrial waste disposal and comprehensive utilization > Food Industry

Preparation of Carboxyl Groups Modified Waste Beer Yeast and Its Adsorption Behavior for Proteins

Author ZhangLi
Tutor LiBuHai;SunXiaoMei
School Central South University for Nationalities
Course Analytical Chemistry
Keywords biosorbent waste beer yeast modification succinic anhydride α-methyl acrylic protein adsorption
CLC X792
Type Master's thesis
Year 2011
Downloads 37
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Proteins and enzymes play an important role in various life activities of organisms. The research of protein has important theoretical and practical significance in guiding industrial production and understanding the laws of life and medical practice. However, we must achieve successful protein purification firstly. So the research of protein purification is significance. Biosorption method has been widespread concern, because it is simple and low cost. Waste beer yeast is a waste of wine industry generated, it contains the same functional groups on the surface of viable cells. It is a natural biosorbent, but the shortcomings such as small size, lower adsorption capacity and difficult separation from liquid phases limit its widespread using. In this paper, we prepared new biosorbents by modifing a series of small molecules containing carboxyl on the surface of waste beer yeast. These biosorbents are characterized by many methods. We study the performance of these modified yeasts on the adsorption of lysozyme, BHb and BSA. Specifically as follows:1. We modified the succinic anhydride on the surface of waste beer yeast by changing the feed ratio and reaction medium. When the feed ratio is 1:3 (yeast: succinic anhydride) and the medium is pyridine, the grafting rate reach 41.3%. The modified yeast is characterized by IR and XPS spectra. The results indicated that succinic anhydride was successfully modified on the surface of waste beer yeast. The best adsorption conditions of lysozyme is 30℃, 6 h and pH 7.0. The maximum lysozyme adsorption capacities of the modified and unmodified yeast are 848.0 mg g-1 and 102.0 mg g-1. The former is the latter 8.3 times. Using Langmuir and Freundlich adsorption model to simulate the isotherm of modified waste beer yeast. The adsorption process of lysozyme is more fitted Langmuir model with monolayer adsorption. The highest desorption ratio (94.2%) is achieved by using 1.0 M NaSCN (pH 7.0) as desorption solution. The purification of lysozyme from chicken egg white is investigated, the ratio of remaining lytic activity of desorbed lysozyme is 91.5%, the total activity recovery is 81.5% and the lysozyme is purified 35.1-fold. The results of electrophoresis analysis indicated that the efficiency for lysozyme purification is good.2. With potassium persulfate as thermal initiator, poly-(α-methyl) acrylic was modified on to the surface of waste beer yeast. The modified yeast is characterized by scanning electron microscopy, IR, XPS spectra and electrometric titration resultingα-methyl acrylic successfully modified on the surface of waste beer yeast. The amount of functional groups is 1.4 m mol g-1. With the modified yeast as adsorbent, the optimal conditions for the adsorption of lysozyme are 30℃, 6 h, pH 7.0. The maximum lysozyme adsorption capacities of the modified and unmodified yeast are 545.0 mg g-1 and 102.0 mg g-1, respectively. The former is the latter 5.3 times. Using Langmuir and Freundlich model to simulate the isotherm of modified and unmodified waste beer yeast. The adsorption process of lysozyme by unmodified yesat is more fitted Langmuir monolayer adsorption model, but not the modified yeast. May be it is the influence of the polymer molecules on the surface of modified yeast. With 1.0 mol L-1 pH 7.0 NaSCN solution as the eluent, elution rate can reach 96.9%. The purification of lysozyme from chicken egg white is investigated, the ratio of remaining lytic activity of desorbed lysozyme is 79.6%, the total activity recovery is 84.0% and the lysozyme is purified 27.1-fold.3. With succinic anhydride modified waste beer yeast as adsorbent, the adsorption behavior of BHb and BSA are investigated. The optimum adsorption conditions are 10 h, pH 5.4, 25℃. The maximum adsorption capacity of modified yeast for BHb is 566.2 mg g-1, however, the maximum adsorption capacity of unmodified yeast for BHb is only 23.5 mg g-1, the former is the latter 24.1 times. Using Langmuir and Freundlich adsorption model to simulate the isotherm of modified waste beer yeast. The adsorption process of BHb is more fitted Langmuir model. The highest desorption ratio is achieved 60% by using 1.0 M NaCl (pH 8.0 Tris-HCl buffer solution) as desorption solution. The purification of BHb from fresh processed bovine blood samples is investigated, the desorption ratio can be increased to 98.4% by second adsorption and desorption. The content of BHb in fresh processed bovine blood samples is 36.3%, but the content increase to 91.5% after purification, the enrichment factor is 2.52. The results are satisfactory.4. Withα-methyl acrylic modified waste beer yeast as adsorbent, the adsorption behavior of BHb and BSA are investigated. The adsorbent almost has no adsorption for BSA. When under the conditions, such as 24 h, pH 5.4, 25℃, the maximum adsorption capacity of modified yeast for BHb is 244.6 mg g-1. It is 10.4 times of that of the unmodified yeast. Using Langmuir and Freundlich adsorption model to simulate the isotherm of modified and unmodified waste beer yeast. The adsorption process of BHb is more fitted Langmuir model. The highest desorption ratio (62.1%) is achieved by using 1.0 M NaCl (pH 8.0 Tris-HCl buffer solution) as desorption solution. The purification of BHb from fresh processed bovine blood samples is investigated, the desorption ratio can be increased to 88.6% by second adsorption and desorption. The content of BHb in fresh processed bovine blood samples is 36.3%, but the content increase to 78.7% after purification, the enrichment factor is 2.17. The results are satisfactory.

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