Sunlight-mediated synthesis of silver nanoparticles using <i>Bacillus paramycoides</i> -associated cellulase as reductant and its role in corncob biomass saccharification

This study explored the green biosynthesis of silver nanoparticles (AgNPs) using cellulase from
Bacillus paramycoides
strain KASHA and assessed their catalytic efficacy for the saccharification of corncob biomass. AgNPs were biosynthesized under sunlight exposure, which turned from colorless to dark red. Successful biosynthesis of AgNPs was ascertained through various characterization techniques. UV-Vis spectroscopy revealed a surface plasmon resonance peak at 425 nm. Fourier transform-infrared (FT-IR) spectroscopy revealed functional groups participating in bioreduction reactions. Zeta potential analysis (-25.5 mV) indicated excellent colloidal stability. Dynamic light scattering analysis revealed a major particle size of ∼86 nm, while scanning electron microscopy (SEM) analysis revealed a predominantly spherical shape. Corncob biomass was treated with NaOH (1-5% w/v) and subsequent microwave irradiation (2 min), resulting in substantial structural changes, as evidenced by FT-IR, X-ray diffraction (XRD), and SEM analysis. Enzymatic hydrolysis of untreated and pre-treated biomass was carried out using both crude cellulase and cellulase-mediated AgNPs. AgNPs demonstrated superior catalytic activity compared to crude cellulase, with substantial improvement in pre-treated biomass. AgNPs showed higher total reducing sugar yield (9.53 ± 0.17 mg/g) at 48 h using 4% NaOH pre-treated biomass, while the highest saccharification efficiency (85.77 ± 0.8%) was also achieved under similar conditions. Overall, the results clearly show that the bacterial cellulase-mediated AgNPs have a significant effect on the hydrolysis of lignocellulosic biomass, providing a promising approach for efficient bioconversion of corncob into fermentable sugars and promoting second-generation bioethanol production.