ESTIMATION OF FUNGAL CONTAMINATION OF CEREAL GRAINS AS DETERMINED BY MEASURING GLUCOSAMINE CONCENTRATION

Abstract

The degree of fungal contamination of a grain or feed sample can be estimated from the determination of its glucosamine (GlcN) content, using a modified amino acid analysis procedure. A sample (100 mg) was hydrolyzed in 6 N HCl for 7 h at 121 °C, evaporated to dryness, reconstituted in citrate buffer and applied to an ion exchange column of an amino acid analyzer. Hydrolysis conditions were optimized for the recovery of GlcN, released by the breakdown of chitin, a major fungal cell wall component. The GlcN and galactosamine (GalN) concentrations of several species of fungi indigenous to western Canada, grown on liquid culture, were determined to provide reference values for estimating fungal contamination. A fungal contamination index (FCI) is proposed, based on a comparison of the GlcN concentration of a sample to the specific reference fungus (if the fungal species has been characterized) or an average from several species. Based on the fungal species tested, a suggested average for use with most naturally contaminated grain samples is 76 mg GlcN g −1 of fungal dry matter. This approximation would be valid for most cases of mixed or unknown fungal species. Knowing the fungal content of a grain sample will aid in feed formulation and thereby reduce costly losses to the livestock producer. Key words: Fungal contamination, glucosamine, chitin, grain, amino acid analysis