Microalgae-associated bacteria play a key role in the flocculation of Chlorella vulgaris.
Flocculation is most preferred method for harvesting microalgae, however, the role of bacteria in microalgal flocculation process is still unknown. This study proves that bacteria play a profound role in flocculating by increasing the floc size resulting in sedimentation of microalgae. A flocculating activity of 94% was achieved with xenic Chlorella vulgaris culture as compared to 2% achieved with axenic culture. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene of xenic C. vulgaris culture revealed the presence of Flavobacterium sp., Terrimonas sp., Sphingobacterium sp., Rhizobium sp. and Hyphomonas sp. as microalgae-associated bacteria. However when Flavobacterium, Terrimonas, Sphingobacterium were eliminated by fluorescence activated cell sorter (FACS), flocculating activity reduced to 3%. Further studies with cell free extracts also suggest that bacterial extracellular substances might also have a role in enhancing flocculation. We conclude that the collective presence of certain bacteria is the determining factor in flocculation of C. vulgaris.
Environmental Biotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahak-ro, Yuseong-gu, Daejeon 305-806, Republic of Korea.
Jimin
J
Lee
Dae-Hyun
DH
Cho
Rishiram
R
Ramanan
Byung-Hyuk
BH
Kim
Hee-Mock
HM
Oh
Hee-Sik
HS
Kim
D019149:Bioreactors / Q000382:microbiology*; D048408:Chlorella vulgaris / Q000302:isolation & purification* / Q000502:physiology*; D005427:Flocculation; D058086:Microalgae / Q000302:isolation & purification* / Q000502:physiology*