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

Abstract

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 H2SO4, HNO3, CH3COOH, HCl, NaOH, Ca(OH)2, KOH, NH3, and H2O2, 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% H2SO4 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, (NH4)(H2PO4), and ZnSO4 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.

Optimization of Alkali Treatment for Production of Fermentable Sugars and Phenolic Compounds from Potato Peel Waste Using Topographical Characterization and FTIR Spectroscopy

“…The thermochemical treatment proved more effective in the monomerization of polymeric sugars of PPW. Several studies have indicated higher yields of useful compounds from the alkali and alkali-plus-steam treatment of PPW [47,[49][50][51][52]. The linear and the quadratic effects of the variables studied and their interaction on the response yield was observed using analyses of variance (ANOVA).…”

“…However, other means to improve the saccharification efficiencies of the procedures reported here, such as varying steam pressures, might be employed to increase the yields. Soni et al [47] have explored various conditions by using different alkali and acid concentrations to treat PPW and assessing their potential to produce bioethanol. They reported 368.53 mg/g of RS after 72 h using alkali-treated PPW, and after enzymatic hydrolysis ethanol concentration was recorded as 19.9g/L.…”