Peel Waste Valorization through Bioconversion into Antioxidant Rich Materials

The growing amount of fruit and vegetable peel wastes has become an environmental and economic problem but the
wastes contain bioactive compounds, with possible health advantages. This paper analyzes the valorization of peel
waste by solid-state fermentation (SSF) and submerged fermentation (SmF) with three microbial strains Aspergillus
niger, Saccharomyces cerevisiae and Bacillus subtilis, to bioconvert the waste into antioxidant-containing substances.
The analysis was done on four types of peel which included orange, banana, mango and pomegranate based on the
total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity (DPPH and ABTS assays). The
outcomes proved that SSF significantly increased bioactive components, as TPC (46.7-70.8 mg GAE/g banana; 46.7-
70.8mg GAE/g pomegranate) and TFC (24.8mg GE/g banana; 24.8mg GE/g pomegranate) were shown to be higher.
Pomegranate peel had the highest DPPH and ABTS radical scavenging activities of 82.7% and 85.3 in SSF,
respectively. A. niger was the most useful microbial strain in enhancing the antioxidant level. There were good positive
correlations between TPC/TFC and antioxidants activity (r > 0.91, p < 0.001). This paper identifies the opportunity of
peel waste bioconversion as a natural antioxidant production method of food, pharmaceutical, and cosmetic use that
can be eco-friendly and cost-effective, ensure the sustainable utilization of waste and encourage the circular
bioeconomy