Influence Of Hydrochloric Acid Concentration On Reducing Sugar Yield And Fermentation Ph In Sweet Potato Peels Hydrolysis

Abstract

Introduction: Acid hydrolysis remains one of the most effective methods for converting starchy and lignocellulosis feedstocks into fermentable sugars as compared to physical and thermal methods. This study determines the effect of HCl concentration on reducing sugars and pH after hydrolysis, after fermentation and the amount of reducing sugar consumed. Methodology: Sweet potato peels (Ipomoea batatas) were collected, washed, dried for 10 days, and mechanically crushed to reduce particle size. Twenty grams of the sample was hydrolyzed using hydrochloric acid at concentrations of 0.2 M, 0.5 M, 1.0 M, 1.5 M, and 2.0 M, heated in a water bath at 98 °C for 2 hours, and autoclaved at 121 °C for 15 minutes. The hydrolysates were filtered and stored for analysis. pH was measured using a calibrated pH meter, while reducing sugars were quantified spectrophotometrically using the alkaline copper tartrate and arsenomolybdate method with standard glucose solutions for calibration. Results: Hydrochloric acid concentration significantly influenced reducing sugar yield and pH (Kruskal– Wallis, p < 0.05). The highest reducing sugar after hydrolysis (28.77 g/L) and consumption during fermentation (21.83 g/L) occurred at 0.5 M HCl, while the lowest yield after hydrolysis was observed at 2.0 M (18.03 g/L). Post-hoc analysis revealed that most acid concentration pairs differed significantly, except for 0.2 M vs 2.0 M and 0.5 M vs 1.0 M in reducing sugar after fermentation. Higher acid concentrations (≥1.0 M) tended to maintain higher post-fermentation pH (3.70), whereas lower concentrations resulted in more acidic conditions (pH 3.20–3.30). Conclusion and Recommendations: The findings indicate that hydrochloric acid concentration has a significant effect on the amount of reducing sugars released during hydrolysis, the quantity consumed during fermentation, and the resulting pH levels. It is therefore recommended that excessively high HCl concentrations be avoided during hydrolysis, as these can lower sugar availability and, in turn, reduce fermentation efficiency