Direct screening of multifunctional Bacillus amyloliquefaciens for fiber degradation, antifungal activity, and its role in promoting wheat straw decomposition and peanut seedling growth

Abstract

Abstract

Decomposed wheat straw is a promising seedling substrate but is vulnerable to contamination by filamentous fungi, notably Aspergillus flavus. Multifunctional microbes that combine strong cellulolytic capacity with antifungal activity are needed to enable cleaner bioprocessing and reduce mycotoxin risk. This study sought to identify such a strain and verify its performance from screening to crop-relevant application. From 2,102 Bacillus isolates collected between 2018 and 2023, we selected Bacillus amyloliquefaciens SQ1 exhibiting both cellulolytic activity and antifungal efficacy against A. flavus. During straw decomposition, SQ1 accelerated cellulose and hemicellulose loss, decreased C/N and lignin/N ratios, and rapidly shifted pH toward neutrality. SQ1 suppressed fungal proliferation; Cryo-SEM revealed fractured and collapsed A. flavus hyphae with markedly reduced spore adhesion. Transcriptomic profiling of A. flavus under SQ1 exposure revealed coordinated repression, spanning cell-envelope biogenesis and sterol synthesis (down-regulation of fks1, aflY, erg2, erg11), diminished developmental competence (ligA), and attenuated toxin regulation (aflR). SQ1-amended decomposed straw reduced the relative abundance of Aspergillus and lowered aflatoxin B1 (AFB1, C₁₇H₁₂O₆) content. Using the SQ1-amended decomposed straw as a substrate improved peanut seedling survival, plant height, and leaf chlorophyll. SQ1 functions as a dual-purpose biocatalyst, breaking down cellulose while inhibiting fungal growth to enhance straw biotransformation, mitigate mycotoxin risk, and support early crop growth. These findings highlight a sustainable and value-added approach to wheat straw utilization, with practical implications for improved substrate management and cleaner production in crop systems.

Graphical abstract

Keywords

Wheat straw / Microbial decomposition / Peanut seedlings / Antifungal activity / Aspergillus flavus / Aflatoxin B1

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Funding

Qinghai Province Key R&D and Transformation Plan of China(no. 2025-NK-130)

RIGHTS & PERMISSIONS

Jiangnan University