Valorization of coffee byproducts for bioethanol production using lignocellulosic yeast fermentation and pervaporation
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Industrial residue management is a critical element of sustainable development. The aim of this research was to investigate the potential of different coffee waste fractions for bioethanol fermentation and its purification by pervaporation; these fractions and the role of pervaporation in this application have not been studied before. Bioethanol production from different coffee waste fractions has now been studied by acid or acid and enzymatic hydrolysis. The fermentation was conducted using two different yeasts (baker’s yeast and lignocellulosic yeast). By using the cellulolytic enzymes and lignocellulosic yeast, a higher bioethanol yield was achieved. Further purification of the fermented filtrate was carried out by an alcohol selective pervaporation membrane at four temperatures (23, 30, 40 and 50 °C). Hydrolysis of the samples using cellulose complex and β-glucosidase enzymes and fermentation with lignocellulosic yeast, followed by purification using pervaporation resulted a superior bioethanol yield of 51.7 ± 7.4 g/l for spent coffee and 132.2 ± 40 g/l for husk. Husk hydrolysis using cellulolytic enzymes and fermentation with lignocellulosic yeast, followed by product recovery through pervaporation membrane, was found to be the optimal procedure, producing ethanol at a concentration of 132.2 ± 40 g/l. In general, husk hydrolysis using acid and cellulolytic hydrolysis and fermentation with lignocellulosic yeast GSE16-T18 followed by pervaporation was found to be the best process for producing the highest ethanol yield compared to the other fractions of coffee waste samples.
KeywordsCoffee waste Enzymatic hydrolysis Pervaporation membrane Pretreatment Purification
High-performance liquid chromatography
Defected coffee bean
Ethanol produced after pervaporation
Biological oxygen demand
Chemical oxygen demand
The authors would like to thank coffee processing industry owners, managers and workers for their cooperation during sample collection. Finally, they would like to thank the VLIR-UOS project of Jimma University for financial support.
This work has been supported by the Institutional University Cooperation Program (IUC) VLIR-UOS project of Belgium and Jimma University, Ethiopia.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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