EFFECTS OF CULTURE CONDITIONS ON DIBENZOFURAN PRODUCTION BY CULTURED MYCOBIONTS OF LICHENS

Two dibenzofurans, isostrepsilic acid and hypostrepsilic acid, were pr oduced in large quantities by the mycobiont of Usnea orientalis cultur ed on a malt-yeast extract medium containing sugar alcohols. The natur al lichen growing in the field produces usnic and salazinic acid but n ot the above dibenzofurans. Isostrepsilic acid is a new product which has shown to be y-9-hydroxymethyl-1-methydibenzofuran-2-carboxylic aci d. It seems that the production of these compounds is probably due to the combined effects of the high osmotic pressure of the medium and th e nutritional conditions. The production of the dibenzofurans was mark edly repressed by actively photosynthesizing photobionts.