Production of Bioethanol from Maize Cob (Zea mays) Using Different Pretreatment Strategies and Fermentation Methods with Saccharomyces cerevisiae and Zymomonas mobilis

Abstract

Maize cob is an abundant lignocellulosic agricultural residue with potential as a non-edible feedstock for bioethanol production, although its recalcitrant structure limits enzymatic conversion. This study evaluated different chemical and physicochemical pretreatments, enzymatic hydrolysis and fermentation strategies for bioethanol production from maize cob. Pretreated biomass was hydrolysed using commercial cellulase and fermented through Separate Hydrolysis and Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF) using Saccharomyces cerevisiae and Zymomonas mobilis under controlled conditions. Pretreatment significantly influenced cellulose, hemicellulose, lignin, ash content, solid loss, sugar release and ethanol production. The combination of 4% NaOH and 5% H₂O₂ (N2P1) produced the highest cellulose content (61.84%) and reduced the lignin content to 7.68%. This treatment also achieved the highest ethanol yield of 12.70% under SSF using S. cerevisiae. The highest SSF ethanol yield obtained using Z. mobilis was 12.15% with 4% NaOH and 1% H₂SO₄ (N2H1). SSF generally produced more ethanol than SHF, while combined alkali-based pretreatments performed better than the control and individual treatments. Correlation analysis showed positive associations between cellulose, sugar fractions and ethanol yields, whereas lignin and ash were negatively associated with conversion performance. Overall, combined pretreatment followed by SSF, particularly N2P1 with S. cerevisiae, was the most effective tested approach for bioethanol production from maize cob.