Biomass production, crudewater-soluble polysaccharide (WSP), ash content, mineral profile, and crude protein content were determined for Lentinus edodes mycella grown on whey permeate (WP)-based medium with lactose content of 4.5% of defined synthetic medium, and harvested after 5, 10, 15, or 20 d of fermentation at 25 degrees C. Harvesting time and the type of media interact to alter the chemical content of mycelia. Mycelia grown in WP had greater (P < 0.05) WSP and ash than mycelia grown in synthetic media. A maximum production of WSP was obtained on the 10th day (4.1 x 10(2) +/- 71 mg WSP/g dried mycelia) from mycelia grown on the WP-based media. Mycelia grown on WP harvested on the 20th day had the highest value in ash content (18 +/- 3%). Potassium was found to be the mail constituent in the ash of mushroom mycelia, which was followed by phosphorus, sodium, calcium, and magnesium. A steady increase of ash content was only noted in mycelia grown in the control media regardless the harvesting time. Data in this research suggested that WP was more favorable than the synthetic media in the production of WSP, which is traditionally known for their medicinal value in L edodes.