Fumonisin B2 production by Aspergillus niger in Thai coffee beans

During 2006 and 2007, a total of 64 Thai dried coffee bean samples (Coffea arabica) from two growing sites in Chiangmai Province and 32 Thai dried coffee bean samples (Coffea canephora) from two growing sites in Chumporn Province, Thailand, were collected and assessed for fumonisin contamination by black Aspergilli. No Fusarium species known to produce fumonisin were detected, but black Aspergilli had high incidences on both Arabica and Robusta Thai coffee beans. Liquid chromatography (LC) with high-resolution mass spectrometric (HRMS) detection showed that 67% of Aspergillus niger isolates from coffee beans were capable of producing fumonisins B2 (FB2) and B4 when grown on Czapek Yeast Agar with 5% NaCl. Small amounts (1-9.7 ng g-1) of FB2 were detected in seven of 12 selected coffee samples after ion-exchange purification and LC-MS/MS detection. Two samples also contained FB4. This is the first record of freshly isolated A. niger strains producing fumonisins and the first report on the natural occurrence of FB2 and FB4 in coffee.