Scale-Up of Tailor-Made Onsite Enzyme Blend From Cassava Peels for Industrial Bioethanol Production.

Abstract

Bioethanol production is one of the key alternatives for fossil fuel use due to climate change. The study seeks to upscale tailor-made onsite enzyme blends for the bioconversion of cassava peels to bioethanol in simultaneous saccharification and fermentation (SSF) process using cassava peels-degrading fungi. The starch and cellulose contents of peels were determined. The results showed significant levels of cellulose (39.78%) and starch (31.21%), indicating that cassava peels are valuable raw materials for bioethanol production. To investigate cassava-degrading microbes, Aspergillus niger demonstrated the highest enzyme activity with a diameter of zone of clearance of 16 mm. Tailor-made enzyme blends were produced with the A. niger using various substrate concentrations (1%, 3%, 5%, 8%, and 10%) of milled cassava peels at periods of 2, 4, 6, 8, and 10 days with a spore concentration of 2.1 × 10⁵ cells/mL. The amylolytic and cellulolytic activities were determined as 4.759 U/mL and 4.265 U/mL, respectively, at 5% and 6-day optimal conditions. The enzyme blend was upscaled using three fermentation vessels, thus 0.250 L flask, 1.0 L flask, and 10 L fermenter at optimized conditions in the SSF process for bioethanol production. These optimal conditions were firstly applied to a 0.250 L flask in the SSF process, a fixed enzyme dose of 20 mL and 1.5 g of Saccharomyces cerevisiae with varying substrate concentrations of 5%, 10%, and 20% and ethanol analyzed daily for 10 days. The theoretical ethanol yields recorded were 15.64%, 16.02%, and 14.91% for 0.250, 1, and 10 volumes obtained at different fermentation days. These optimized conditions demonstrate the potential for industrial bioethanol production in Ghana.