Ellagic acid production by Aspergillus niger in solid state fermentation of pomegranate residues

Abstract

Two Aspergillus niger strains (GH1 and PSH) previously isolated from a semiarid region of Mexico were characterized for their effectiveness in converting pomegranate ellagitannins (ET) into ellagic acid (EA) in a solid state fermentation (SSF). Pomegranate seeds and husk were used as support for the SSF. Released EA was evaluated by liquid chromatography. Yields of 6.3 and 4.6 mg of EA per gram of dried pomegranate husk were obtained with A. niger GH1 and PSH, respectively. Total hydrolyzable polyphenols of pomegranate husk were degraded during the first 72 h of culture (71 and 61%, by GH1 and PSH strains, respectively). Tannin acyl hydrolase activity was not clearly associated with EA production. EA that accumulated in cultures of A. niger GH1 was remarkably pure after a simple extraction process. Pomegranate husk is a good support, and at the same time an excellent substrate in the production of high commercial interest metabolites like EA due the degradation of its ET content.