Prospecting Filamentous Fungi for Amylase Production: Standardization of Aspergillus japonicus Culture Conditions

Abstract

Aims: Prospecting different filamentous fungi for high production of amylases in standard conditions for future application in biotechnology industries. Methodology: Samples were collected in different field areas in the state of Bahia, Brazil, for isolating filamentous fungi. Fungi were grown in Petri dishes in a culture medium containing 4% Quaker® oatmeal and 2% bacteriological agar. Fungi screening was carried out in liquid medium containing 1% starch at 30°C and pH6.0 under static conditions for 4 days. Proteins and enzyme activities were determined by Bradford and DNS methods, respectively. A submerged fermentation was performed with different liquid media in order to obtain the best growth composition and enzyme production for the selected fungus. Several conditions such as time course of inactivation, pH, temperature, carbon and nitrogen sources were determined in the culture medium with the aim of improving amylase production and fungi growth. Various fibers and food residues were used as enzymatic inducers in a way to assess potential integration of this enzyme, producing microorganisms in the food industry. Results: A. japonicus proved to be the best degrader of fibers and food residues. After 4 days, A. japonicus enzyme production was maximal, with 44.65(±0.49) U/ml under static conditions. The maximal enzyme activity was obtained at pH 6.0, retaining its activity even at a higher pH. The optimum temperature was 25°C. The best carbon source was potato starch and the best food residues were orange bagasse and bark for the enzyme production by A. japonicus. Conclusion: The results suggest that A. japonicus is a good amylase producer for the degradation of fibers and food residues, indicating that it might become important for the food industry, bringing value to what is known as waste these days.