Exploring the Potential of Potato Peels for Bioethanol Production through Various Pretreatment Strategies and an In-House-Produced Multi-Enzyme System

This study aimed to explore the viability of converting potato peel waste into bioethanol using a custom-produced multi-enzyme preparation. Various pretreatment approaches were employed on the potato peels, including thermal, chemical, and thermo-chemical methods. These methods involved boiling for 30 and 60 min, steaming at different pressures and durations, and applying different concentrations of chemicals, including H 2 SO 4 , HNO 3 , CH 3 COOH, HCl, NaOH, Ca(OH) 2 , KOH, NH 3 , and H 2 O 2 , either individually or in combination with steam treatment. The pretreated potato peels were subsequently subjected to enzymatic hydrolysis using a crude multi-enzyme cocktail obtained from solid-state fermentation of wheat bran by a naturally occurring strain of Aspergillus niger P-19. This enzyme cocktail consisted of cellulases, hemicellulases, pectinase, and amylases. The most effective pretreatment combination involved the use of 3% H 2 SO 4 followed by steam treatment under pressure, and enzymatic hydrolysis utilizing the crude multi-enzyme preparation. This combination resulted in the highest concentration of reducing sugars (141.04 ± 12.31 g/L), with a carbohydrate conversion rate of 98.49% when a substrate loading of 20% was used. As a result, an ethanol yield of 43.2 ± 3.82 g/L, representing 21.6% based on dry matter, was achieved. Furthermore, supplementing the medium with peptone, (NH 4 )(H 2 PO 4 ), and ZnSO 4 at a concentration of 0.1% w / v each, along with solid loadings of 22% and 24%, respectively, achieved yield improvements of 51.67 g/L and 54.75 g/L. However, the maximum productivity of 23.4% was observed with a 22% loading, compared to a yield of 22.8% with a 24% solid loading, based on dry matter.