| Summary: | <i>Delonix regia</i> (common name: Flame tree) pods, an inexpensive lignocellulosic waste matrix, were successfully used to produce value-added bioethanol. Initially, the potentiality of <i>D. regia</i> pods as a lignocellulosic biomass was assessed by Fourier-transform infrared spectroscopy (FTIR), which revealed the presence of several functional groups belonging to cellulose, hemicellulose, and lignin, implying that <i>D. regia</i> pods could serve as an excellent lignocellulosic biomass. Response Surface Methodology (RSM) and Central Composite Design (CCD) were used to optimize pretreatment conditions of incubation time (10–70 min), H<sub>2</sub>SO<sub>4</sub> concentration (0.5–3%), amount of substrate (0.02–0.22 g), and temperature (45–100 °C). Then, RSM-suggested 30 trials of pretreatment conditions experimented in the laboratory, and a trial using 0.16 g substrate, 3% H<sub>2</sub>SO<sub>4</sub>, 70 min incubation at 90 °C, yielded the highest amount of glucose (0.296 mg·mL<sup>−1</sup>), and xylose (0.477 mg·mL<sup>−1</sup>). Subsequently, the same trial conditions were chosen in the downstream process, and pretreated <i>D. regia</i> pods were subjected to enzymatic hydrolysis with 5 mL of indigenously produced cellulase enzyme (74 filter per unit [FPU]) at 50 °C for 72 h to augment the yield of fermentable sugars, yielding up to 55.57 mg·mL<sup>−1</sup> of glucose. Finally, the released sugars were fermented to ethanol by <i>Saccharomyces cerevisiae</i>, yielding a maximum of 7.771% ethanol after 72 h of incubation at 30 °C. Conclusively, this study entails the successful valorization of <i>D. regia</i> pods for bioethanol production.
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