Effects of hydraulic shear stress and oxygen starvation stress an immobilized white-rot fungus Phanerochaete chrysosporium in submerged cultures for ligninase production were studied. The immobilized fungal hyphae formed an even mycelial mat on a rotating cylindrical stainless steel net showing little sensitivity to the shear stress. The average activity of ligninase over 24 h during a peak production period was 389 U/L at a tip velocity of 0.44 mis and 369 U/L at a doubled tip velocity of 0.88 m/s. When the dissolved oxygen level dropped below 1 mg/L, the fungal cells responded to the oxygen starvation stress and released a considerable amount of protease. The proteolytic denaturation of ligninase was the major reason that a negligible ligninase activity was detected at a low aeration rate.