Abstract

Proteolytic enzymes are metabolites that can be produced by microbial sources and develop important functions in food industry as in cheese manufacturing. However, it is necessary to ensure the final product safety by testing toxins production by microorganisms. As a result of this, the aim of this study was to investigate the production of proteases by Aspergillus flavo furcatis DPUA 1608 in submerged and solid state fermentation and also certify the non-production of aflatoxin by this species. The aflatoxin test was carried out using the method of ammonia vapor. In this test, A. flavo furcatis DPUA 1608 was inoculated in seven different media cultures (COA, YES, CZ, CYA, GMS, PMS and PDA) and the production of toxins was confirmed by the color change of culture reverse after adding a 25% (w/v) ammonia solution. The protease production was conducted using four inoculums (SAB+GLI, SAB+SAC, BDA+GLI and BDA+SAC) in three media cultures of submerged fermentation obtained by a base mineral solution (MA01, MAGli and MASac) and in solid state fermentation using açai seeds and rice bran as substrate (SAFA). According to ammonia vapor test, A. flavo furcatis is not an aflatoxin producer. There was no color change in the colonies reverse of any culture media. All crude extracts obtained in both fermentations were tested for protease production. The best protease activity was observed in the medium MA01 (inoculums SAB+SAC, BDA+GLI and BDA+SAC). Milk clotting activity was determined in all crude extracts of submerged and solid fermentation. However, the clot formed was considered as strong milk coagulation only in the media MA01 of submerged fermentation (inoculums SAB+SAC, BDA+GLI and BDA+SAC) and in all inoculums of solid state fermentation (SAFA). A. flavo furcatis DPUA 1608 showed potential milk-clotting protease production in both fermentations media used.

Key words: Ammonia vapor test, Aspergillus, milk-clotting enzymes, liquid fermentation, solid fermentation.