Abstract:

This paper reports the optimization of Aspergillus niger fermentation of sea-buckthorn (Hippophae rhamnoides) fruit slurry for the conversion of flavonoid glycosides into aglycones. The effect of nitrogen source type on the contents of isorhannetin and quercetin in fermentation broth was examined and fermentation temperature and duration, shaking speed and volume percentage of medium occupying fermentor were optimized using orthogonal array design for obtaining maximum sum of the contents of isorhannetin and quercetin in fermentation broth. Soybean dregs were the best choice for maximum aglycone content. The optimal levels of fermentation temperature and duration, shaking speed and volume percentage of medium occupying fermentor were 30 ℃, 96 h, 180 r/min and 40%, respectively, and the resultant contents of isorhannetin and quercetin 78 mg/g and 22 mg/g.

Key words: Hippophae rhamnoides, flavonoid glycosides, aglycone, Aspergillus niger, microbial conversion