Influence of exo β-d-galactofuranosidase inhibitors in cultures of Penicillium fellutanum and modifications in hyphal cell structure

Abstract We have examined β- d -galactofuranosidase production by Penicillium fellutanum in the presence of d -galactono-1,4-lactone or 4-aminophenyl 1-thio-β- d -galactofuranoside, two potent in vitro inhibitors of the enzyme. Activity of the enzyme in the culture filtrate was increased by 35% when glucose was replaced by d -galactose as the carbon source, and the activity diminished 80% of the control value when the inhibitors were added. Significant alterations of the culture were observed: (a) the medium became increasingly opalescent due to the secretion of a protein aggregate (PA) which contained 15% neutral sugar, mainly ribose; (b) the peptidophosphogalactomannan (pPGM) containing galactofuranose, normally produced by P. fellutanum , could not be obtained from the culture medium in the presence of the inhibitors; (c) the content of galactofuranose in the cell wall was significantly decreased in the presence of d -galactono-1,4-lactone. The influence on the mycelia growth was investigated by light microscopy (LM) and transmission electron microscopy (TEM) showing important alterations.