The extracellular polymeric substance (EPS) and soluble
microbial product (SMP) samples were collected according to the
previous study (Gao et al., 2011b), and then extracted based on
the reference (Malamis and Andreadakis, 2009). The content of
polysaccharides was tested by the phenol–sulphuric acid method
(Dubois et al., 1956). Proteins’ concentration was measured by
the Modified BCA kit (Sangon, China).