Extracellular secretions of Phanerochaete chrysosporium on Cd toxicity

• EPS, extracellular protein and oxalate were elevated in some extent to cope Cd2+ toxicity.
• Ligninolytic enzyme activities were general inhibited under cadmium exposure.
• Extracellular CdS crystal was synthesized to reduce the mobility and toxicity of Cd2+.

The extracellular secretions are believed to have a significant influence on microorganisms physicochemical properties related to growth, morphological preservation, and environment stress defense. In this study, the response and potential detoxification role of the extracellular secretions in the widely used white-rot fungus, Phanerochaete chrysosporium, was investigated. The results indicated that the EPS production was elevated and the activities of two main ligninolytic enzymes (LiP and MnP) were generally inhibited by cadmium. At the early exposure period (0–8 h), the extracellular protein was induced by 50 μM cadmium. However, an opposite result was observed with further increase in exposure time. The oxalate secretion under cadmium stress increased by 73.2%–218.4% compared to control. The addition of oxalic acid resulted in elevation in P. chrysosporium viability up to 190.6%, which confirms the detoxification of oxalate. The extracellular secretions such as EPS, extracellular protein and oxalate were elevated in some extent by cadmium, which was probably a stress response for P. chrysosporium to bind cadmium ion and cope the toxicity. Moreover, extracellular biosynthesis of cadmium crystal particles was observed, which is a directly evidence of P. chrysosporium extracellular secretions to reduce the mobility and bioavailability of cadmium ion.