Enzymatic hydrolysis of sugar beet pulp: bridging industrial waste valorization and forest soil ecological restoration

Abstract

Sugar beet pulp (SBP) is a common agricultural waste that can be enzymatically hydrolyzed to produce fermentable sugars and bioactive oligosaccharides. These compounds act as “priming substrates” to regulate the rhizosphere microbial community and enhance plant-soil feedback (PSF) mechanisms. This study investigated the potential of integrating SBP microbial hydrolysis to address degraded soil restoration challenges, particularly in saline environments. The aim was to explore how metabolic priming of Klebsiella sp. HDJT1 via glucose and sulfur supplementation enhances cellulolytic enzyme production and modulates rhizosphere microbial networks to improve soil health. Results demonstrated that glucose pre-cultivation of HDJT1 increased endo-β-glucanase activity by 390% and β-glucosidase by 147%, while sulfur supplementation (e.g., sodium sulfide) further enhanced exo-β-glucanase activity. Structural equation modeling revealed that in saline soils, microbial cross-feeding between carbon- and sulfur-metabolizing guilds (e.g., Pseudomonas, Paenibacillus) drove nutrient cycling efficiency, with hemicellulase activity correlating positively with active organic carbon. Notably, the addition of HDJT1 increased cation exchange capacity (CEC) and catalase activity, enhancing nutrient retention and antioxidant capacity. The study highlights the synergistic role of SBP-derived oligosaccharides and sulfur metabolism in reprogramming rhizosphere microbiomes, promoting plant-microbe interactions under stress. This strategy offers a dual benefit: valorizing industrial waste (e.g., SBP) while restoring degraded forest soils through targeted microbial priming, demonstrating a potential proof-of-concept approach that warrants field validation for ecological rehabilitation in saline soil regions.

Graphical abstract

Keywords

Forest soil bioremediation / Plant-soil feedback / Rhizosphere microbiome / Soil health / Carbon–sulfur cross-feeding

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