Enhancing the degradation of cellulose and hemicellulose in chili pepper straw waste using Cellulomonas iranensis 7–12, which was isolated from naturally decayed chili pepper straw

Abstract

The sustainable valorization of agricultural waste, such as chili pepper straw, is often challenged by the absence of effective microbes that can degrade cell wall components. In this study, metagenomic analysis found that Pseudomonadota was the dominant phylum in the carboxymethyl cellulose (CMC)-enriched microbial communities. In addition, a cellulolytic bacterial strain, designated as Cellulomonas iranensis 7–12, was isolated from naturally decayed chili pepper straw and identified by colony morphology, Gram staining, 16 S rRNA gene sequencing, and genome-based average nucleotide identity (ANI) analysis. Within 30 h, C. iranensis 7–12 displayed robust cellulolytic activity, causing nearly complete disintegration of filter paper, a cellulose model substrate. In contrast, chili pepper straw, a structurally more complex lignocellulosic substrate, was only partially degraded, with dry-weight loss increasing from 11.98% in the uninoculated control to 32.63% after 4 d of fermentation with C. iranensis 7–12. C. iranensis 7–12 exhibited a predominantly extracellular cellulase–xylanase activity profile, with extracellular xylanase activity reaching 3.41 U/mL and exceeding the measured cellulase activities. Whole-genome sequencing of C. iranensis 7–12 identified a complete 3.79-Mb circular chromosome and a diverse CAZyme repertoire, including glycoside hydrolase families related to cellulose and hemicellulose degradation, carbohydrate-binding modules, carbohydrate esterases, and secretion-associated proteins. Moreover, scanning electron microscopy (SEM) examination revealed that the surface and internal microstructure of chili pepper straw were disrupted. Similarly, Fourier-transform infrared (FTIR) spectroscopy analysis showed marked changes in the characteristic absorption bands associated with cellulose, hemicellulose, and lignin-containing structures, indicating partial degradation of polysaccharide components and lignin-associated structural alteration. Collectively, C. iranensis 7–12 shows great potential for the bioconversion of chili pepper straw and the high-performance microbes will be further developed for the effective use of biomass resources.