Cellulolytic activity in Aspergillus spp. contaminating livestock feeds and raw materials

Abstract

The contamination by Aspergillus spp. have become a global concern in food and feedstuffs and can lead to a reduction in yield and quality of agricultural products with significant economic losses. Most species of Aspergillus produce cellulose-degrading enzymes and some of them also have mycotoxigenic activity. This study aimed i) to evaluate the Aspergillus contamination in feeds (16) and row materials (32) collected in Sicily; ii) to isolate and identify fungi belonging to the genus Aspergillus and iii) to analyze their ability to produce cellulolytic enzymes. Aspergillus spp. contamination was evaluated on PDA using serial ten-fold dilution and spread plate technique (Mirabile et al., 2019) and ranged from 50 to 9x106 CFU/g and from 45 to 3,3x107 in feeds and raw materials, respectively. The most recurrent colonies were identified by morphological features, ITS and β-tubulin sequence analysis as A. niger, A. tubingensis, A. brasiliensis, A. fumigatus and A. flavus. Qualitative production of cellulolytic enzymes performed according to Mandels et al. (1976) and time course of endo and exo-β-1,4 glucanase activity (UI/ml) determined in solid submerged fermentation (Ghose, 1987), revealed a variability between Aspergillus species and was strain-dependent. A. tubingensis SAAF14, A. flavus MUCL18903 and A. brasiliensis MUCL20039 exhibited the highest CMCase and FPase activity of 2.16, 2.37 and 0.99 UI/ml and 0.65, 0.92, and 0.42 UI/ml, respectively. The presence of these Aspergillus isolates with high cellulolytic activity could represent a potential risk for the quality of the contaminated food.