Integrated Fermentation of Fruit Processing Wastes into Bioethanol by <i>Saccharomyces Cerevisiae </i>and <i>Aspergillus</i> <i>Niger</i>

The detrimental environmental impact of fossil fuels, primarily driven by harmful greenhouse gas emissions, necessitates the urgent development of sustainable alternative energy sources. Concurrently, effective municipal solid waste management, particularly concerning organic fractions, presents a significant challenge in urban centers like Arba Minch, Ethiopia. This research addresses both issues by investigating the valorization of locally abundant fruit peel waste specifically from bananas and mangoes—into bioethanol, a viable renewable fuel. The study employed a bioprocessing strategy utilizing microbial co-culture. Waste peels were pre-processed by chopping into 3-5 cm pieces, followed by seven days of sun-drying to facilitate milling and enhance substrate accessibility. The resulting dried powder, rich in fermentable cellulose and hemicellulose, served as the primary feedstock. Bioethanol production was achieved through a seven-day simultaneous saccharification and fermentation (SSF) process using a co-culture of <i>Aspergillus niger</i> (for enzymatic hydrolysis/saccharification) and <i>Saccharomyces cerevisiae</i> (for ethanol fermentation). The fermentation media was maintained at a pH of 5.5-6.0 and a temperature of 30°C. An initial phase involved agitation on a dry shaker for two days to ensure mixing and oxygen transfer for microbial growth, followed by static incubation to promote anaerobic fermentation. Post-SSF, the broth underwent distillation to recover the bioethanol. Qualitative analysis confirmed ethanol production, while quantitative yield was determined spectrophotometrically. Results demonstrated that the mixed inoculum of <i>A. niger</i> and <i>S. cerevisiae</i> achieved a substantial ethanol yield of 79% from the mixed peel substrate after seven days. Notably, comparative analysis revealed that <i>A. niger</i> monoculture fermentation produced a significantly higher yield of 77% ethanol relative to <i>S. cerevisiae</i> alone. This work successfully establishes a practical method for converting problematic fruit peel waste from Arba Minch into valuable biofuel, highlighting the particular efficacy of <i>A. niger</i> in this process.