Hexosamine biosynthesis and accumulation by fungi in liquid and solid media

Abstract

Hexosamine biosynthesis and incorporation into polysaccharides glyco-proteins have been studied in four species of fungi— Aspergillus niger, Penicillium citrinum, Cladosporium cladosporoides, and Fusarium moniliforme. Hydrolytic, recovery, and analytical methods are described for the estimation of hexosamine accumulation in fungal growth. Optimum yields of hexosamine from matrix are achieved by using hydrolysis with strong acid (8 M hydrochloric acid) over a period of 2–3 h. For all fungal-growth studies, hexosamine was quantitated, after hydrolysis, by an automated, amino acid analyzer programmed for the separation of amino sugars. Methods were also developed, using gas-liquid chromatography (nitrogen-selective alkaline flame-ionization detector and trimethylsilyl derivatives of hexosamines), and the modified Morgan-Elson reaction of N-acetylated hexosamines. Both the amino acid analyzer and gas-chromatographic method quantify nmol amounts of hexosamine per mg of dry-weight sample. In all phases of the growth cycle, a linear correlation was found for the four fungi between the amount of hexosamine per unit time, age of culture, and quantity of mycelial biomass in liquid medium. With solid corn-meal as a fungal growth-medium, samples also demonstrated a linear correlation, but only between hexosamine biosynthesis and age of culture, as biomass was not determinable. Autolysis of hexosamine occurs to only a limited extent during late stationary-phase in liquid medium and on corn.