Catalytic properties of amylases produced by Cunninghamella echinulata and Rhizopus microsporus

The present work aimed to characterize and compare the catalytic properties of amylases from Cunninghamella echinulata and Rhizopus microsporus. The highest production of amylase by C. echinulata, 234.94 U g^-1 of dry substrate (or 23.49 U mL^-1), was obtained using wheat bran as a substrate, with 50–55% initial moisture and kept at 28 °C for 48 h. The highest production of amylases by R. microsporus, 224.85 U g^-1 of dry substrate (or 22.48 U mL^-1), was obtained cultivating wheat bran with 65% initial moisture at 45 °C for 24 h. The optimal activity of the amylases was observed at pH 5.0 at 60 °C for C. echinulata enzymes and at pH 4.5 at 65 °C for R. microsporus. The amylases produced by C. echinulata were stable at pH 4.0–8.0, while the R. microsporus enzymes were stable at pH 4.0–10.0. The amylases produced by C. echinulata remained stable for 1 h at 50 °C and the R. microsporus amylases maintained catalytic activity for 1 h at 55 °C. The enzymatic extracts of both fungi hydrolyzed starches from different plant sources and showed potential for liquefaction of starch, however the amylolytic complex of C. echinulata exhibited greater saccharifying potential.

Key words
agro-industrial residues; amylase production; amylolytic enzymes; solid-state cultivation