3.2. Macromolecules degradation
The high COD removal indicated that Z08 degraded macromolecules directly. In the initial soybean wastewater (Table 1), macromolecules (MW > 10,000 Da) counted for 86% of the total TOC while small molecules (MW < 650 Da) counted for only 12%. After 72 h treatment, macromolecules decreased by 75.5% while small molecules increased. Correspondingly, the wastewater COD decreased by 86%. Clearly, Z08 directly utilized macromolecules for
metabolism, which was quite different from the traditional theory that PSB could only utilize small substances (Imhoff and Trper,1989). The difference might be caused by different materials tested. Protein and fat were used to examine the PSB utilization potentials in other studies (Imhoff and Trper, 1989) while soybean wastewater rich in various nutrients, trace metals, and balanced with small, medium and macro molecules was used in this study (Table 1).