Simultaneous saccharification and fermentation of municipal cardboard waste for bioethanol production using immobilized cellulases and xylanases onto Cu-MOF

This study aims to establish a cost-effective and environmentally friendly method for bioethanol production by optimizing enzymatic hydrolysis of cardboard waste, a significant component of municipal solid waste, in combination with fermentation by Saccharomyces cerevisiae. The use of a cellulases and xylanases enzyme blend, sourced from Thermobifida fusca and Bacillus pumilus, respectively, enhances saccharification efficiency. Pre-treatment with 2 % NaOH results in a substantial 66 % saccharification efficiency at a 5 % solid/substrate loading. Further improvement in hydrolysis efficiency is achieved through enzyme immobilization on Cu-BTC-MOFs, which were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Field Emission Scanning Electron Microscopy (FESEM). The immobilized enzyme blend increases saccharification efficiency to 78 %, compared to 66 % for free enzyme systems. Reusability studies demonstrate a gradual reduction in saccharification efficiency across successive cycles, reaching 71.29 % by the twelfth cycle. When applied in a simultaneous saccharification and fermentation (SSF) setup under optimized conditions, the system yields a notable bioethanol production with a yield of 0.55 g/g and a productivity of 0.20 g/L·h. This study offers potential applications in sustainable bioethanol production and waste valorization by enhancing enzymatic hydrolysis and fermentation of municipal cardboard waste. The approach demonstrates promise for scaling bioenergy production and contributes to addressing waste management challenges, supporting green energy initiatives.