[Development of a novel green treatment process for n-eicosane based on the spent mushroom substrate-immobilized...

Bioaugmentation is a widely employed strategy for addressing petroleum contamination. However, exogenous strains often struggle to effectively colonize contaminated sites due to their poor environmental adaptability, which constrains the efficacy of remediation efforts. To address the challenges of sustaining long-term activity of exogenous microbial strains and the pressing need for green treatment of the spent mushroom substrate, that is agriculture waste. In this study, we explored the utilization of agricultural waste, specifically spent mushroom substrate, as an innovative immobilization carrier for the development of efficient alkane-degrading microbial agents. The preparation process was optimized by the orthogonal method. Experimental findings indicated that the mushroom substrate had the cellulose crystallinity reaching 73.63%, functional groups such as hydroxyl and carboxyl, and high concentrations of soluble nutrients, serving as an appropriate microbial carrier. Furthermore, an alkane-degrading bacterial strain, Pseudomonas sp. MJ, was isolated and immobilized on the spent mushroom substrate to formulate an immobilized microbial agent. The optimal preparation conditions were determined as follows: immobilization duration of 72 h, a mushroom substrate particle size of 0.25-0.30 mm, and a carrier-to-strain ratio of 1:4 (M/V). Under these conditions, the mushroom substrate-immobilized microbial agent demonstrated excellent strain retention capability and long-term stability. After storage at 4 ℃ for 30 d, the bacterial load remained at 1.05×10¹⁰ CFU/g. Moreover, the agent demonstrated excellent alkane degradation proficiency, with the degradation rate of 500 mg/L N-eicosane within 72 h reaching 95.80%, which is 11.24 times that of the free strain. This study presents an efficient immobilized microbial agent for the bioremediation of alkane pollution and introduces a novel approach for the sustainable treatment of agricultural waste, specifically spent mushroom substrate.