Oxalate production at different initial Pb2+ concentrations and the influence of oxalate during solid-state fermentation of straw with Phanerochaete chrysosporium

► Oxalate production at different initial Pb2+ concentrations was investigated. ► Moderate level of Pb2+ induces more production of oxalate. ► More oxalate production is with better Pb2+ passivation effect. ► More oxalate production is with more effective changes in lignin degradation system.