Title : Oil-derived Bacillus exopolysaccharides as sustainable protective eco-barriers for reversing climate-driven topsoil moisture depletion
Abstract:
Climate-driven topsoil moisture depletion and accelerating environmental desiccation present severe threats to global agricultural sustainability, soil structural integrity, and food security systems. To combat these intensifying challenges, there is a critical ecological need to engineer eco-friendly, biodegradable macromolecular protective solutions capable of preserving soil hydration architectures. This study focuses on isolating, screening, and profiling resident high-yielding exopolysaccharide-producing soil bacteria to serve as native, functional topsoil eco-barriers. Soil samples collected across variable garden sites exhibiting a pH range of 7.0 to 8.6 (average pH 7.5) revealed a robust aerobic heterotrophic bacterial load ranging between 3.6×107and 8.8×107cfu/g colony-forming units per gram on Luria-Bertani agar medium. Out of twelve potential bacterial isolates evaluated via phenotypic Congo Red assay channels, three highly efficient strains were confirmed as potent exopolysaccharide producers. Advanced genetic identification utilizing sixteen-S ribosomal ribonucleic acid gene-based sequencing recognized these isolates within the genus Bacillus, specifically designated as Bacillus subtilis BDIFST240015, Bacillus velezensis BDIFST240016, and Bacillus stercoris BDIFST240017. Optimization studies identified Bacillus stercoris BDIFST240017 as the most potent biopolymer producer, achieving a substantial yield of 178.2 mg/L. Following batch fermentation and extraction processes, the structural and chemical compositions of the harvested biopolymers were thoroughly evaluated. Ultraviolet spectroscopy and Fourier-transform infrared spectroscopy confirmed a highly pure polysaccharide matrix characterized by an exceptional carbohydrate content of 921.84 µg/5 mg. Functional characterization assays demonstrated that the isolated Bacillus stercoris matrix possesses a remarkable water-holding capacity of 103.01%, an oil-holding capacity of 112.24%, and a water solubility index of 12.13%. These parameters establish a strong, highly cohesive texture and stabilizing capacity vital for creating stable soil hydro-matrices. Furthermore, independent antioxidant protocols confirmed a powerful 57.8% DPPH free-radical scavenging activity and a strong Fe3+ reducing power, highlighting its ability to mitigate oxidative stress in drought-affected micro-environments. The biopolymer also functioned as an effective emulsifier, demonstrating optimal 24 hour emulsification indices with diverse lipid systems and hydrocarbons, including n-hexane, coconut oil, and soybean oil. Conclusively, deploying these native bacterial matrices offers a highly sustainable, scalable, and resilient bioengineering intervention to establish protective topsoil eco-barriers, effectively reversing moisture depletion and enhancing long-term agricultural soil resilience globally.
Keywords: Exopolysaccharide (EPS), Bacillus Stercoris, Microbial Biopolymer, Eco-Barriers, Soil Moisture Retention, Antioxidant Activity.
