Effect of temperature on flocculation
The biopolymer WD161 was incubated at the temperature range of 30–80 °C and the flocculating capability was determined. The flocculating activity and flocculation rate increased with increasing temperature up to 40 °C (Table 5). In comparison with the above experiment, their flocculating activities further increased by 7.2% in kaolin suspension (16.5), and 30.5% in decanter effluent (12.4). However, their flocculation rates were not influence by temperature as the values were similar to the above experiment (93.9% in kaolin suspension, and 91.8% in decanter effluent). The structure of protein bioflocculants would be destroyed when heating, hence the protein bioflocculants are considered thermal unstable. For instance, when heated at 100 °C for 30 min, the protein bioflocculant NOC-1 produced from Rhodococcus erythropolis was deactivated, with a 50% decrease in flocculating capability [32]. If the major component of a bioflocculant is a glycoprotein, its stability will depend on the relative contents of protein and polysaccharide [20], such as polyglutamic acid (PGA) from Bacillus sp. DYU1 [18]Bacillus sp. PY-90 [16] and B. licheniformis CCRC12826