SELECTION AND QUANTIFICATION OF Aspergillus welwitschiae AND Aspergillus niger STRAINS PRODUCING AMYLASES

Garlic (Allium sativum L.) is one of the most consumed food products in Brazil, however it may present risk factors to human health, as it is often subject to fungal infections. Data from the literature show a predominance of fungi of the Aspergillus genus, in which some isolates of certain species may be producers of mycotoxins under favorable conditions, such as fumonisin B2 and/or ochratoxin A. On the other hand, some species of the Aspergillus genus stand out as the production of hydrolytic enzymes, such as amylases and lipases, of great industrial and biotechnological interest. Among the numerous enzymes synthesized by fungi, amylases are of great importance because they have a wide industrial application. In this sense, the objective of this study was to verify the potential of amylases production by 25 strains previously identified as Aspergillus welwitschiae and Aspergillus niger. The strains used in this study were isolated from commercial garlic obtained from 12 Brazilian states and were selected according to previous results regarding the potential of not producing ochratoxin A fumonisin B2. Initially the 25 strains were evaluated semi-quantitatively for the potential of amylase production in Czapeck-Dox agar medium containing 2% starch at 25 °C for 5 days, followed by a new incubation for 10 days. The evaluation of lipase production was performed in experimental triplicate by detection of degradation halos revealed with 1% iodin solution and their evaluation with the Enzymatic Index (IE). At the same time, the potential of amylase production quantitatively was measured in liquid Czapeck-Dox medium containing 2% starch, incubated at 25 °C for 5 days and detected by reducing sugar dosage (DNS-3,5-dinitrosalicylate) at A540nm. The results obtained allowed to verify that the 25 strains were producing amylases. However, the strains UEL As 15.262, UEL As 20.290 and UEL As 4.82 were the higher amylase producers (IE-1.61, IE-1.50, and IE-1.56, respectively) by the semi-quantitative method ( IE), whereas the UEL As 34,462, UEL As 28,430 and UEL As 29,432 strains (1.69 mg / mL, 1.44 mg / mL and 1.24 mg / mL, respectively) were the higher amylase producers by the method quantitative (DNS). The UEL As 15.262 and UEL As 34.462 strains were selected for future studies to evaluate the best abiotic conditions for the production of amylases.