Harvest of Scenedesmus sp. with bioflocculant and reuse of culture medium for subsequent high-density cultures.

The optimal flocculating conditions for harvesting high-density cultures of Scenedesmus sp. were investigated using inorganic coagulants and the bioflocculant produced by Paenibacillus polymyxa AM49. The flocculated medium as nutrients for subsequent algal cultivation was also tested. Consecutive treatment with 8.5 mM CaCl(2) and 0.2 mM FeCl(3) as coagulants and 1% bioflocculant from the culture broth of P. polymyxa AM49 showed the highest flocculating activity of up to 95% for high density algal cultures. The medium flocculated with the coagulants and bioflocculant showed less than 8% decrease in the growth yield in the subsequent algal cultivation. Furthermore, a 20% or 50% fresh BG11 medium supplement allowed the flocculated medium to maintain a high growth yield in subsequent algal cultivation. These results suggest that the flocculation method presented here is efficient and bio-friendly, and allows the reuse of the flocculated medium, thereby contributing to the economic cultivation and harvest of microalgae.

Klebsiella pneumoniae KE-1 degrades endosulfan without formation of the toxic metabolite, endosulfan sulfate.

For bioremediation of toxic endosulfan, endosulfan degradation bacteria, which do not form toxic endosulfan sulfate, were isolated from various soil samples using endosulfan as sole carbon and energy source. Among the 40 isolated bacteria, strain KE-1, which was identified as Klebsiella pneumoniae by physiological and 16S rDNA sequence analysis, showed superior endosulfan degradation activity. Analysis of culture pH, growth, free sulfate and endosulfan and its metabolites demonstrated that KE-1 biologically degrades 8.72 microg endosulfan ml(-1) day(-1) when incubated with 93.9 microg ml(-1) endosulfan for 10 days without formation of toxic endosulfan sulfate. Our results suggest that K. pneumoniae KE-1 degraded endosulfan by a non-oxidative pathway and that strain KE-1 has potential as a biocatalyst for endosulfan bioremediation.