Phenotypic characterization and pan-genomic analysis of a novel bioflocculant-producing Stenotrophomonas maltophilia PT-13 for wastewater treatment

Microbial bioflocculants (MBFs) are eco-friendly alternatives, yet the species-level genetic basis of heteropolysaccharide-type MBFs biosynthesis remains largely unclear. In this study, a novel high-efficiency MBF-producing bacterial strain Stenotrophomonas maltophilia PT-13 was isolated. Fermentation conditions and flocculation operational parameters were systematically optimized using single-factor experiments combined with response surface methodology (RSM). Results showed that the optimal flocculation conditions yielded a kaolin flocculation efficiency of 90.3% with RSM. Bioflocculant MBF-PT produced by S. maltophilia PT-13 was identified as an acidic heteropolysaccharide mainly composed of rhamnose, glucose and mannose, with flocculation governed by adsorption-bridging supplemented by charge neutralization. In simulated domestic wastewater, MBF-PT achieved 74.2% (chemical oxygen demand)、81.3% (turbidity) and 80.4% (suspended solids) removal efficiencies. Pan-genomic analysis revealed an open pan-genome of S. maltophilia and identified conserved core gene clusters responsible for polysaccharide synthesis, glycosyl transfer and transmembrane transport. This study provides a promising microbial resource for developing green water treatment agents and offers new insights into the species-level genetic mechanism of MBFs biosynthesis.