How solid-state fermentation with <i>A. niger</i> changes agro-waste of apple, aronia and sea buckthorn to attractive antioxidant compounds

Abstract This work focuses on the influence of solid-state fermentation on the polyphenols and flavonoids conent in fruit pomace of apple, aronia, and sea buckthorn. A comparison was made during a seven-day fermentation of pomace with A. niger and with autochthonous microflora, showing that this method has no significance for aronia and sea buckthorn pomace. Autochthonous microflora had a more favorable effect on the content of polyphenols and flavonoids than A. niger. However, in the case of apple pomace, the content of total polyphenols increased up to 1425 mg GAE/100 g DW on the seventh day of fermentation with A. niger , representing a 7.3-fold increase compared to the initial value of 195 mg GAE/100 g DW. Our results therefore present an attractive way of agro-waste utilization and the subsequent implementation of these isolates in other types of industry.