Fermentation duration critically shapes microbial performance and energy use in lignocellulosic ethanol. This study explores the time course of simultaneous saccharification and co-fermentation (SSCF) by Saccharomyces cerevisiae (ATCC 200062) and Scheffersomyces stipitis (ATCC 58785) using alkali-pretreated oil-palm empty fruit bunches (EFB). A Rotating Centre Composite Design was applied, with the central point positioned at the midpoint of the experimental factors. A total of 20 experimental runs were generated, covering the following ranges: NaOH concentration (1–3 %), temperature (100–140 °C), and reaction time (40–80 min). Time-resolved curves show that, under most conditions, ethanol production plateaus around 89 h, with only a small additional increase by 120 h; glucose is the main driver of early ethanol production, while xylose residue depends on specific conditions, and energy consumption increases linearly over time. Using responses at 89 h, NaOH loading emerges as the dominant pretreatment factor, and a moderate-severity region near ∼2 % NaOH, ∼120 °C, and ∼ 60 min balances solid recovery, fermentability, and energy-normalized productivity (ENP). Therefore, it is recommended to use approximately 89 h as the fermentation endpoint, along with a moderately alkaline pretreatment method, to balance ethanol yield and energy efficiency. This study establishes an energy-based optimized production framework for fermentation time and pretreatment conditions in lignocellulosic ethanol production, thereby guiding the efficient production of industrial bioethanol.
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