Inhibition of Microcystis aeruginosa using Brevundimonas sp. AA06 immobilized in polyvinyl alcohol-sodium alginate beads

Abstract

Application of algicidal bacteria is a potential bio-technique to inhibit harmful algal growth and remove algal blooms. At present, algicidal bacteria are mainly used in the form of freely suspended cells. In this study, the bacterium Brevundimonas sp. AA06 against Microcystis aeruginosa was isolated from soil and the algicidal effects of immobilized strain AA06 were investigated. The spherically immobilized beads (φ = 3.0~4.0 mm) were prepared by polyvinyl alcohol (PVA) and sodium alginate (SA). Scanning electron microscopy (SEM) images of polyvinyl alcohol-sodium alginate (PVA-SA) beads showed that there were a large number of pores inside and that the bacterial cells adhered to the skeleton. Cyanobacterial dose-relationship tests showed that the PVA-SA beads exhibited weaker algicidal effects than freely suspended cells. At an initial M. aeruginosa cell density of 2.0 × 109 cells/L, PVA-SA beads inhibited the growth of M. aeruginosa for up to 60 days, which was much longer than freely suspended cells (34 days). When M. aeruginosa was exposed to PVA-SA beads at EC70,96h (concentrations for 70% of maximal algicidal effect after 96 h), the total microcystin-LR (MC-LR) concentrations (intra and extra cellular) remained stable at 40.0±5 μg/L, with intracellular MC-LR concentrations declining.