Determination of Sugar Present before and after Fermentation from Dovyalis Caffra and Musa Species peels Mixture

Abstract

The ever-increasing depletion and rising cost of fossil fuel reserves and the environmental consequences associated with their use have intensified search for sustainable and renewable energy alternatives such as bioethanol. Fruit waste and agricultural residues are particularly attractive feedstocks because they are abundant, inexpensive, and do not compete directly with food resources. Among these potential raw materials, Dovyalis caffra (Kei apple) and Musa species peels are of interest because they contain carbohydrates and reducing sugars that can be converted into ethanol through fermentation. This study evaluated the potential of a mixture of Dovyalis caffra and Musa species peels as a low-cost substrate for bioethanol production by assessing fermentable sugar content before and after fermentation. This study employed an experimental approach in which ripe fruits of Dovyalis caffra were sourced from different farms while Musa species peels were collected from different markets in Nairobi. The fruit extracts and pretreated peels were then mixed in ratios of 5:5, 6:4, and 7:3 and subjected to fermentation using Saccharomyces cerevisiae. Key parameters optimized were temperature (25°C, 30°C, and 35°C) and pH (4.5, 5.0, and 5.5). Sugar content was determined using the Brix method. Data collected were analyzed using ANOVA and considered statistically significant at p ≤ 0.05. Results indicated a significant reduction in sugar content ranging between 31.23 g/L and 80.91 g/L after fermentation, consistent with microbial utilization of fermentable sugars. Temperature had a pronounced effect, with the highest sugar reduction observed at 35°C, followed by 30°C, while the lowest occurred at 25°C. Optimal pH for fermentation was 5.0, which resulted in greater sugar consumption compared to pH 4.5 and 5.5, although variations were relatively small. Among the mixture ratios, 6:4 (Dovyalis caffra: Musa species peels) showed slightly higher sugar reduction, though the effect of ratio was less significant compared to temperature and pH. The highest overall sugar reduction was achieved at 35°C, pH 5.0, and a 6:4 mixture ratio. Statistical analysis confirmed that temperature, pH, mixture ratio, and their interactions significantly influenced sugar conversion (p < 0.05). The findings indicate that Dovyalis caffra and Musa species peels contain substantial fermentable sugars, suggesting potential as a substrate for bioethanol production; direct quantification of ethanol yield is required to confirm this potential. This study highlights the potential of utilizing fruit waste for renewable energy generation, contributing to waste management and reduced reliance on fossil fuels. Further research is recommended to quantify actual ethanol yield, optimize fermentation conditions, evaluate production efficiency at larger scales, and explore practical applications in sustainable energy systems.