This study was to investigate the stimulating effect of Rhodotorula mucilaginosa yeast co-culture on the laccase production of Pleurotus ferulae JM301 in liquid fermentation. Among the 49 tested microbial strains, only the R. mucilaginosa significantly enhanced the laccase production. Maximal laccase production of 10575 U/L was attained with the inoculation of 5.0 x 10(9) R. mucilaginosa cells to P. ferulae at 48 h. The possible mechanisms proposed previously for laccase overproduction (glucose starvation and glycerol as second carbon source) were unable to explain the enhanced laccase production of the co-culture in this study. The rough surface of P. ferulae mycelia in the monoculture became relatively smooth in the co-culture with R. mucilaginosa and the co-culture also resulted in an increase in the total protein concentration. Overall, the study showed that co-culture with R. mucilaginosa increased the laccase production of P. ferulae in association with the changes in mycelial morphology and protein secretion. (C) 2015 Elsevier Ltd. All rights reserved.