Dynamics of organohalogen production by the ecologically important fungus Hypholoma fasciculare

Abstract

The ecologically important white rot basidiomycete Hypholoma fasciculare was previously shown to produce large amounts of adsorbable organic halogens (AOX). The purposes of this study were to identify the time period of AOX production in relation to the primary and secondary metabolic phases of the growth cycle of the fungus, to determine the maximal specific AOX production rates and final AOX yields on the different substrates and to account for the measured AOX in identifiable compounds. The AOX production was observed to take place during the transition between the primary and secondary metabolic phases of the growth cycle of the fungus. The maximum AOX production rates ranged from 0.63 to 3.23 mg AOX per gram of dry mycelium per day and the final AOX yields ranged from 0.88 and 1.50 percent of dry weight of mycelium on five different substrates including natural woody substrates. The AOX produced by the fungus was stable in all five substrates, even after prolonged incubation periods. However, the composition of the AOX changed drastically. Initially most of the AOX was accounted for by the compound 3,5-dichloro- p-anisyl alcohol; however, after prolonged incubation this compound was largely converted into 3,5-dichloro- p-anisic acid in N-rich medium and into unidentified organohalogens in N-limited medium.