Valorization of Delonix regia Pods for Bioethanol Production

Delonix regia (common name: Flame tree) pods, an inexpensive lignocellulosic waste matrix, were successfully used to produce value-added bioethanol. Initially, the potentiality of D. regia 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 D. regia 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), H2SO4 concentration (0.5-3%), amount of substrate (0.02-0.22 g), and temperature (45-100 degrees C). Then, RSM-suggested 30 trials of pretreatment conditions experimented in the laboratory, and a trial using 0.16 g substrate, 3% H2SO4, 70 min incubation at 90 degrees C, yielded the highest amount of glucose (0.296 mg center dot mL(-1)), and xylose (0.477 mg center dot mL(-1)). Subsequently, the same trial conditions were chosen in the downstream process, and pretreated D. regia pods were subjected to enzymatic hydrolysis with 5 mL of indigenously produced cellulase enzyme (74 filter per unit [FPU]) at 50 degrees C for 72 h to augment the yield of fermentable sugars, yielding up to 55.57 mg center dot mL(-1) of glucose. Finally, the released sugars were fermented to ethanol by Saccharomyces cerevisiae, yielding a maximum of 7.771% ethanol after 72 h of incubation at 30 degrees C. Conclusively, this study entails the successful valorization of D. regia pods for bioethanol production.

Automated summary

Flame tree pods were used to produce value-added bioethanol, with optimization of pretreatment conditions and enzymatic hydrolysis, resulting in a maximum ethanol yield of 7.771% after fermentation.