To prepare a novel biosorbent, we modified waste beer yeast with citric acid using NaH2PO4 as catalyst in N,N-dimethylformamide. We characterized the absorbent using Fourier transform infrared and X-ray photoelectron spectroscopy. We examined the factors of pH, temperature, adsorption time, initial lysozyme concentration, and NaCl ionic strength on the adsorption capacity. Based on the Langmuir isotherm, the adsorption capacity of lysozyme was 909.09 mg.g(-1), 11.06-fold higher than that of the unmodified. When it was eluted by 1.0 mol.L-1 NaCl, the desorption efficiency reached 84.8%. We then used the modified waste beer yeast to separate and purify the lysozyme from egg white, and the lysozyme could be purified in 27.5-fold in a single step with a total enzyme activity recovery of 71.3%. In addition, the regenerated biomass could be used again with little loss of the adsorption capacity. We found that the Langmuir model fitted the lysozyme adsorption isotherm better. Taken together, the modified waste beer yeast can purify lysozyme from chicken egg white in a rapid and cost-efficient way.