The chitosan was extracted by using a two-step biological treatment process: demineralization by lactobacillus plantarum and deproteinization by Pseudomonas aeruginosa. Chitosan exhibited a strong antibacterial effect on the gram-positive bacteria than gram-negative since the inhibition rates were 47 and 50% against Staphylococcus aureus and Bacillus cereus, respectively, also the growth inhibition effect by chitosan against fungi was not strong as in the case of bacteria.