Optimization of bio-ethanol production via solid-state fermentation using Saccharomyces cerevisiae PTCC 1212 and fruit and vegetable wastes

Introduction: Global municipal solid waste generation is growing progressively due to social urbanization. Fruit and vegetable waste are a significant part of solid waste. This waste can be recovered to produce biofuels. Saccharomyces cerevisiae is consumed as a first-choice microorganism for industrial processes of alcoholic fermentation.Materials and Methods: The potential of ethanol production by S. cerevisiae PTCC 1212 on a laboratory scale was investigated using fruit and vegetable wastes over solid-state fermentation (SSF) using a colorimetric distilling system. First, we have estimated the ethanol production potential of solid waste substrates taken from the Shahrekord Center of Fruits and Vegetables. Next, and over-optimization experiments, fermentation parameters for ethanol production and yield including substrate type, pH, humidity, inoculum volume, and time of fermentation were evaluated using the Taguchi statistical method. Bioethanol assay was done by the distillation-colorimetric method and sugar consumption was determined using the DNS colorimetric method.Results: Bio-ethanol production contents from solid waste substrates including fruit mix, carrot, potato, cattle food, eating vegetable, and beet molasses as an alcoholic fermentation additive were 2.8, 2.3, 0.98, 0.56, 0.07, and 3.5 (w/v), respectively. The optimized conditions for ethanol production were 4 days of fermentation, pH 6, 90% humidity, and 5% inoculum volume. The ethanol achievement in the final test based on optimized parameters was up to 3.3%. The optimized conditions for the best ethanol yield (ethanol per one gram of substrate) were, pH =5, humidity level as natural (without the addition of water) and substrate mixed fruits plus molasses.Discussion and Conclusion: High sugar rate conversion showed appropriate efficiency in the fermentation process and fruit and vegetable wastes have an exciting potential for bio-ethanol production in solid-state fermentation. It could be considered for environmental challenges with garbage management. Moreover, adding molasses seems to be an appropriate supplement for boosting the production of ethanol.