Co-immobilization in alginate beads of microalgae with microalgae growth-promoting bacterium as a novel approach for removing ammonium and phosphorus ions from wastewater

Luz E. de-Bashan, Juan-Pablo Hernandez, and Yoav Bashan

Environmental Microbiology, The Center for Biological Research of the Northwest (CIB) P.O. Box 128, La Paz, B.C.S. 23000, MEXICO

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Plant growth-promoting bacteria (PGPB) of the genus Azospirillum are known to enhance the growth of numerous agricultural crops. We are proposing the use of these bacteria as “microalgae-growth promoting bacteria” (MGPB) to enhance the cleaning capacity of polluted water by the microalgae Chlorella vulgaris. The deliberate inoculation of Chlorella spp. with a terrestrial PGPB has not been reported prior to these studies, perhaps because of the different origins of the two microorganisms. C. vulgaris is not known to harbor any associative beneficial bacteria, and Azospirillum spp. is rarely used for inoculation in aquatic environments. Co-immobilization of C. vulgaris and A. brasilense in small alginate beads resulted in significant increases in numerous growth parameters of the microalga. Dry and fresh weight, total number of cells, size of the microalgal clusters (colonies) within the beads, number of microalgal cells per cluster, and the levels of microalgal pigments significantly increased (1). The two organisms reside in small cavities within the beads and mutually affect each other (2). Additionally, lipids and a variety of fatty acids significantly increased (3, 4), and the combination of microalgae and the MGPB had a superior capacity for removing ammonium and phosphorus from polluted waters (5).

We propose co-immobilization of microalgae and plant growth-promoting bacteria as an effective means of increasing microalgal populations and their capacity for cleaning contaminated water.

1. Gonzalez, L.E., and Bashan, Y. (2000) Appl. Environ. Microbiol. 66, 1527-1531.

2. Lebsky, V.K., Gonzalez-Bashan, L.E., and Bashan, Y. (2001) Can. J. Microbiol. 47, 1-8.

3. Gonzalez-Bashan, L.E., Lebsky, V.K., Hernandez, J.P., Bustillos, J.J. and Bashan, Y. (2000) Can. J. Microbiol. 46, 653-659.

4. de-Bashan, L.E., Bashan, Y., Moreno, M., Lebsky, V.K., and Bustillos, J.J. (2002) Can. J. Microbiol. (in press).

de-Bashan, L.E., Moreno, M. Hernandez, J.-P., and Bashan, Y. (2002) Water Research (In press).