Fermented organic wastes with enhanced values: Antioxidant activity, anti-inflammation, anti-diabetes and bioaccessibility

Organic wastes typically contain significant levels of bioactive values that would have negative environmental, economic, and social impacts if improperly managed. This study evaluated the feasibility of Aspergillus niger solid-state fermentation to increase the phenolic content of eleven organic wastes that have not previously been used in solid-state fermentation for polyphenol recovery. Although all materials were shown to support fungal growth during fermentation, significant increases in phenolic content were only observed with banana and pumpkin peel. Solid-state fermentation conditions in terms of fermentation duration, temperature, and moisture content for the highest phenolic content in banana and pumpkin peel were identified as 4 days, 30°C, and 60% for banana peel and 5 days, 30°C, and 50% for pumpkin peel. After fermentation, there were increased levels of catechin, gallic acid and rutin with undetectable levels of mycotoxins in fermented banana and pumpkin peel extract. In addition, fermented banana and pumpkin peel extract was shown to have significantly higher antioxidant activity (radical scavenging and ferric reducing ability), anti-inflammatory capacity (inhibition of protease and protein denaturation), anti-diabetic potential (inhibition of α-glucosidase) and bioaccessibility (gastrointestinal digestion) compared to unfermented control. Overall, the efficacy of solid-state fermentation in improving bioactive values along with bioaccessibility of banana and pumpkin peel extract was demonstrated, with prospective applications in nutraceutical and pharmaceutical industries.