BACKGROUND: Exopolysaccharides (EPS) from mushrooms have many health properties such as anti-tumor effect and immunoenhancing activity. Light-emitting diodes (LEDs) with various light wavelengths (red, yellow, green, blue and white) were applied to study the effects on mycelial growth and EPS production of Pleurotus eryngii. RESULTS: In solid-state culture, red and yellow light showed stimulatory effects on P. eryngii hyphal growth. In submerged culture, darkness was the best condition for biomass production. The highest EPS production was obtained when using blue light, where the EPS production and specific EPS production rates were 455 mg L-1 and 79.8 mg g(-1) dry-cell-weight day(-1), respectively. CONCLUSION: The results indicate that a decreasing biomass and an increasing EPS yield in P. eryngii culture were obtained with decreased light wavelength. (C) 2013 Society of Chemical Industry