Production of free amino acid fertilizer from tung meal by the newly isolated Pseudomonas aeruginosa LYT-4 strain with simultaneous potential biocontrol capacity

Tung meal is the main byproduct generated during tung oil extraction from tung tree (Vernicia fordii) seeds and contains approximately 36–45 wt% crude protein. The disposal of large amounts of this resource has attracted increasing attention in relation to its value-added utilization. In this study, a new strain Pseudomonas aeruginosa LYT-4, was isolated for the bioconversion of tung meal into free amino acid fertilizer. Solid-state fermentation analysis showed that the protease activity of P. aeruginosa LYT-4 treatment was significantly higher than that under natural treatment throughout the fermentation period. The total percentage of free amino acids increased from 46.5% under natural fermentation to 55.5% under P. aeruginosa LYT-4 treatment. Pot experiments revealed that P. aeruginosa LYT-4 fermented-tung meal efficiently promoted spinach growth by increasing biomass and was more effective than both naturally fermented tung meal and chemical fertilizer. Furthermore, P. aeruginosa LYT-4 exhibited efficient in vitro antagonistic activity against three plant pathogens, Colletotrichum lini, Rhizoctonia solani and Fusarium oxysporum, possibly due to the abundant secondary metabolite clusters in its genome based on genomic analysis. In conclusion, P. aeruginosa LYT-4 exhibited a promising prospect for the industrial production of free amino acid fertilizer from tung meal with simultaneous potential biocontrol capacity.