Effects of carbon source on expression of alcohol oxidase activity and on morphologic pattern of YR-1 strain, a filamentous fungus isolated from petroleum-contaminated soils

Abstract

Soluble alcohol oxidase (AO) activity was detected in the supernatant fraction of a high-speed centrifugation procedure after ballistic cellular homogenization to break the mycelium from a filamentous fungus strain named YR-1, isolated from petroleum-contaminated soils. AO activity from aerobically grown mycelium was detected in growth media containing different carbon sources, including alcohols and hydrocarbons but not in glucose. In previous work, zymogram analysis conducted with crude extracts from aerobic mycelium of YR-1 strain indicated the existence of two AO enzymes originally named AO-1 and AO-2. In the present study, we were able to separate the AO-1 band into two bands depending on culture conditions, carbon source, and polyacrylamide gel electrophoresis (PAGE) separation conditions; the enzyme activity pattern in zymograms from cell-free extracts exhibited three different bands after native PAGE. New nomenclature was used for upper bands AO-1 and AO-2 and lower band AO-3, respectively. The expression of AO activity was studied in the absence of glucose in the culture media and in the presence of hydrocarbons or petroleum as sole carbon source, suggesting that AO expression could be subjected to two regulatory possibilities: carbon catabolite regulation by glucose and induction by hydrocarbons. The possibility of catabolic inhibition of AO by glucose in the active enzyme was also tested, and the results confirm that this kind of regulatory mechanism is not present in AO activity.