Phytase Production of Aspergillus Niger on Soybean Meal by Solid-State Fermentation Using a Rotating Drum Bioreactor

Abstract

Soybean meal is an agro-industrial residue which is used as a substrate to produce the enzyme phytase by Aspergillusniger in solid-state fermentation. Phytase is a biocatalytic enzyme widely used in the animal feed industry. The aim of this study was to investigate the growth of A. niger and its production of phytase in two systems: 500 mL Erlenmeyer flasks (EF) and a 600 L rotating drum bioreactor (RDB). The highest phytase activity found was about 1,200 unit/g substrate dry weight in EF and 580 unit/g substrate dry weight in RDB. In solid-state fermentation it is necessary to control temperature and substrate moisture content to optimize A. niger growth and its production of phytase. This study confirmed that temperature and moisture content of substrate could be controlled to optimize the result during fermentation in a 600 L RDB. In this study, inlet air velocity was controlled at 1.5 m/s and the rotational speed at 1.0 rpm in solid-state fermentation. The crude enzyme produced by A. niger in solid-state fermentation was achieved in a 600 RDB after 36 h of fermentation. This crude enzyme was dried in a hot air oven at 50^oC for 3 d prior to use in animal feed. Phytase activity was found to be 1.5-fold lower than the activity obtained before drying the crude enzyme.