Biotransformation of agar extraction waste into cultivation matrix using an adaptively evolved Paenibacillus mucilaginosus strain.

Industrial agar extraction waste (AEW), which consists of resistant K-rich perlite and agar-dominated seaweed residues, poses environmental challenges. In this study, we isolated K-solubilizing bacteria from an AEW storage yard and identified the adaptively evolved strain, ZK03-Aga1, with efficient K-solubilizing and agar-utilizing properties. Co-fermentation of ZK03-Aga1 with AEW significantly enhanced the production of oligosaccharides, K, and soluble solids. These products, combined with a commercial soilless matrix, form a composite matrix that has been validated for fertility through bok choy planting experiments. The results showed increased bok choy yield, energy, protein, trace element, and chlorophyll content. Bacterial community composition analysis indicated an increase in nitrogen-fixing and organic matter-degrading bacteria. This suggests that AEW nutrients, via ZK03-Aga1 fermentation, directly benefit crops, improving yield, quality, and microbial structure for sustainable fertility. This study presents an efficient method for reusing AEW and mitigating its environmental impacts.