Flocculation characteristics of a bioflocculant produced by the actinomycete Streptomyces sp hsn06 on microalgae biomass

Background: Microbial flocculation is a good choice for harvest of microalgae biomass, which has gained extensive attention. There have been carried out massive studies in bacterial flocculation, many bacterial strains with flocculation activity were isolated and different types of bioflocculants were produced. However, harvest of algal biomass by bioflocculants which produced from actinomycete are deficiency. In this study, the bioflocculant from an actinomycete Streptomyces sp. hsn06 could be used to harvest Chlorella vulgaris biomass. Results: Consecutive treatment with 20 mg.L-1 bioflocculant and 5 mM CaCl2 for 5 min showed the highest flocculating activity. The bioflocculant was a nonprotein substance with thermal stability and pH stability, which can be used in comprehensive applications. Chemical analysis of the bioflocculant indicated that it is a small molecule substance of moderate polarity with containing triple bond and cumulated double bonds. Algal temperature, pH, and metal ions showed great effects on the flocculation efficiency of the bioflocculant. Conclusions: The bioflocculant produced by Streptomyces sp. hsn06 possesses the potential to harvest algal biomass with high-efficiency.