Growth and fermentation responses of Phanerochaete chrysosporium to O2 limitation

Phanerochaete chrysosporium BKM-F-1767 produced small amounts of ethanol from glucose, mannose, cellobiose, maltose and sucrose when grown with a limited O2 supply in sealed bottles. Under O2-limited growth on glucose, low levels of acetate or oxalate were produced when nitrogen was in excess or limited, respectively. Alcohol dehydrogenase activity (15 nmol/min/mg extract protein) was detected in cell extracts made from ethanol producing cells. The low levels of fermentative enzymes and products indicate that P. chrysosporium does not grow fermentatively, but probably survives transient oxygen limitation by fermentation. Analysis of the genome sequence has indicated multiple alcohol dehydrogenase genes that resemble ADH I and ADH II. Fermentation experiments conducted with 1-13C- and 2-13C-glucose produced 2-13C- and 1-13C-ethanol, respectively. Under conditions of 1-13C-glucose incubation with nitrogen in excess 2-13C-acetate was also detected. The labeling pattern is consistent with ethanol formation by glycolysis and alcohol dehydrogenase. Ethanol was detected in aspen chips aerobically colonized by P. chrysosporium only when the culture was purged with nitrogen gas. The data indicate that P. chrysosporium is able to ferment components of wood when the supply of O2 is depleted.