Investigating rice straw-based solid acid catalyst to hydrolyze cellulosic materials for biohydrogen production using Enterobacter aerogenes

The main goal is to investigate the effect of catalytic hydrolysis using sulfonated activated carbon compared to enzymatic hydrolysis of cellulosic compounds to produce hydrogen and ethanol using Enterobacter aerogenes. Activated carbon as a precursor for acidic solid catalyst was obtained from alkali-treated rice straw. The physicochemical and morphological properties of sCK-Ar were investigated using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray, and Brunauer–Emmet–Teller (BET) analysis. The sulfonic and total acidic site density in sCK-Ar was assessed using CHNS elemental analysis and NH₃-Temperature programmed desorption (NH₃-TPH) method. A soft porous structure of sCK-Ar with a surface area of 754.91 m²/g and different acidic functional groups (hydroxyls, carboxyls, and sulfonic) with a density of 3.01 mmol/g was observed. Among different cellulosic substrates tested, catalytic hydrolysis was more effective on the hydrogen production from pretreated microcrystalline cellulose, so that the produced H₂ from catalytic hydrolysate was 77.43 mL/g which is 4.95 times larger than the hydrogen production from non-catalytic hydrolysate. Also, among different alkali pretreated RS samples, the best improvement of the fermentation products was obtained for KOH pretreated and enzymatically hydrolyzed sample about 136.29 mL/g hydrogen and 5.12 g/L ethanol.