Selection of Non-Mycotoxigenic Inulinase Producers in the Group of Black Aspergilli for Use in Food Processing

Research background. Inulinases are used for fructooligosaccharide production and they are research topic for scientific community and for industry too. Black aspergilli represent a diverse group of species which has use for enzyme production, in particular some species are known as potent inulinases producers. Finding new potential producers from the environment is as important as improving production with known strains. Safety use of enzymes provided by aspergilli in food industry is placed ahead of their benefit for inulinase production.
Experimental approach. Here we shown specific approach to finding/screening of newly isolated fungal inulinase producers which combine newly developed screening method and an equally important assessment of the toxigenic potential of the fungus. In this study 39 black aspergilli collected from different substrates in Serbia were identified and assessed for inulinases production.
Results and conclusions. The most common species were Aspergillus tubingensis (51.2 %), followed by A. niger (23.1 %), A. welwitschiae (23.1 %), and A. uvarum (2.6 %). Selection of the isolates for inulinases production was conducted using a cheap and easy, fast and non-hazardous alternative inulinase screening test developed in this work. For selected inulinases producing strains enzymatic activity was confirmed spectrophotometrically. Since some A. niger and A. welwitschiae are able to produce mycotoxins ochratoxin A (OTA) and fumonisins (FB), the toxigenic potential of selected inulinases producers was assessed analytically and genetically. Fungal enzyme producer could be considered as food safety only after crossing results of both approaches for toxic potential - the direct presence of mycotoxins in the enzyme preparation (analytically) and a presence of genes clusters (genetically). In some strains absence of OTA and FB production capability was molecularly confirmed by absence of complete or critical parts of biosynthetic gene clusters, respectively. The two best inulinases producers and mycotoxin non-producers (without mycotoxin production capability as additional safety) were selected as potential candidates for further development of enzyme production.
Novelty and scientific contribution. Presented innovative approach for selection of potential fungal enzyme producer shows that only non-toxigenic fungi could be considered as useful in food industry. Although this study was done on local isolates, the approach is applicable globally.