Preparation Of Small Molecule Acid Modified Waste Beer Yeast And Its Adsorption Behavior For Proteins

Protein has an extremely important role in organism’s development and growth process.With the development of modern science and the growth of human needs, the requirements ofquality and purity are becoming more and more demanding in science and clinical trial. Dueto the particularity of biological materials, most protein exists in the multi-component systemswith unsteady property. Biosorption is a potential method for seperation and purification ofproteins, due to simple operation and equipment, short process time and low cost. Thedevelopment of new、good selectivity、high efficiency and cheapness sorbents is still the hotissues for researchers. Waste beer yeast is a by-product of brewing industry, which is rich inhydroxyl and amino groups. It has been widely considered as low-cost biomass to treat wastewater. In order to improve the adsorption ability, it is common to graft active groups onto thebiomass surface to increase active binding sites. The aim of the introduction is to promoterecycling and conserving resources, finding wildly application and friendly environmentalmaterial, so as to promote further developments. Here we modified cross-linked waste beeryeast with different small molecule acids and then evaluated its adsorption behavior forlysozyme、bovine serum albumin、bovine hemoglobin. The main work about the biosorptionfor proteins is summarized as follows:1. To prepare a novel biosorbent, we modified waste beer yeast with citric acid usingNaH2PO4as catalyst in N, N-dimethylformamide. The absorbent was characterized usingFourier transform infrared、X-ray photoelectron spectroscopy and H+titration. The factors ofpH, temperature, adsorption time, initial lysozyme concentration and NaCl ionic strength onthe adsorption capacity were investigated.The results indicated that at pH7.4and25℃,theadsorption equilibrium can be reached for40min. The adsorption capacity of modifiedbiomass for lysozyme is909.09mg.g^-1,while89.9mg.g^-1of unmodified,10.6fold higher thanthat of the unmodified. When it was eluted by1.0mol.L^-1NaCl, the desorption efficiencyreached84.8%. We then used the modified waste beer yeast to separate and purify thelysozyme from egg white, and the lysozyme could be purified in27.5-fold in a single stepwith a total enzyme activity recovery of71.3%. In addition, the regenerated biomass could beused again with little loss of the adsorption capacity. The Langmuir model is better fitted the lysozyme adsorption isotherm.2. maleic anhydride modified absorbents were prepared by using pyridine as solvent,maleic anhydride as modification reagent, then the reaction product was treated withNaHCO3after washing and drying. Phosphoric acid modified absorbents were synthesized byusing N,N-Dimethylformamide and urea as solvent, Phosphoric acid as modificationreagent.The presence of carboxy group on the surface of biosorbents were verified by Fouriertransform infrared、X-ray photoelectron spectroscopy and H+titration.The results showed thatmaleic anhydride and Phosphoric acid have successfully grafted onto the biomass surfacerespectivly. The new adsorbents were utilized to adsorb lysozyme. Experimental results showthat there has been no improvement in the adsorption process for maleic anhydride modifiedbiomass.The maximum adsorption capacity was close to the unmodified biomass, only1.3times higher than that.The acidity of the solution has little effect on phosphate-modifiedbiomass for lysozyme adsorption.the adsorption process was quick and can reach equilibriumfor20min.The maximum adsorption capacity is1423.2mg.g^-1,15.8-fold higher than theunmodified (89.9mg.g^-1). When it was eluted by1.0mol.L^-1NaCl, the desorption efficiencyreached86.2%.The modified waste beer yeast was used to separate and purify the lysozymefrom egg white, and the lysozyme could be purified in29.1-fold in a single step with a totalenzyme activity recovery of65%. We found that the Langmuir model fitted the lysozymeadsorption isotherm better.3.The adsorption behavior for bovine serum albumin has been studied using the citricacid, and maleic anhydride modified waste beer yeast. For the citric acid modifiedbiomass,the optimal adsorption conditions are the following:12h、pH4.0、25℃.Themaximum adsorption capacity was242.6mg.g^-1,7.7-fold higher than the unmodified (31.4mg.g^-1). The optimal adsorption conditions for maleic anhydride modified waste beer yeastare the following:20h、pH6.6、25℃.The maximum adsorption capacity was162.9mg.g^-1,5.2-fold higher than the unmodified (31.4mg.g^-1).The results showed that the Langmuirisotherm fitted better in the adsorption process,which showed that the adsorption of bovineserum albumin is monolayer adsorption.The loaded protein can be eluted69.6%by0.5molimidazole solution.4. The phosphoric acid, citric acid and maleic anhydride modified biosorbents were apply to adsorb bovine hemoglobin,respectively. The best acidity for the three adsorbents isat pH5.0,phosphate acid modified biomass can reach equilibrium within a very short time,citric acid modified biomass need for12h.The maleic anhydride modified yeast did notadsorb bovine hemoglobin. Phosphoric acid and citric acid modified yeast own largeadsorption capacity for bovine hemoglobin,309.8mg.g^-1and369.8mg.g^-1,respectively.Adsorption capacity has been greatly improved compared with the unmodified.