Whole-cell immobilization of the hydrocarbon rich microalgae, Botryococcus braunii and B. protuberans, in alginate beads under air-lift batch cultures resulted in a significant increase in chlorophyll, carotenoid, dry weight, and 1ipid contents at stationary and resting growth phases, as compared to free cells. Photosynthetic activity in both the species, of Botryococcus was enhanced, relative to free cells, at any growth phase of cultures. Immobilization exerted a protective influence on ageing of the cultures as reflected by higher chlorophyll and dry weight contents. Entrapment also stabilized the chlorophyll and carotenoid contents even at stationary and resting phases as compared to free cells in both the species.