Abstract: Bacillus pumilus was investigated for its effects on the accumulation of biomass and β-carotene in the culture of Dunaliella salina SZ-05. The results showed that the presence of B. pumilus significantly increased the growth rate and the accumulation of biomass and β-carotene in the culture of D. salina SZ-05, and reduced the dissolved oxygen and exopolysaccharides. The reduction of dissolved oxygen resulted in a decreased photorespiration in alga cells and hence an increased photosynthesis, and consequently an enhanced growth rate and biomass accumulation. Exopolysaccharides were found to be the active agents to quench free radicals. In stress conditions, the reduction of exopolysaccharides might triggered an enhanced biosynthesis of β-carotene, leading to an increased accumulation of β-carotene.

Key words: Bacillus pumilus, Dunaliella salina SZ-05, biomass, &beta, -carotene accumulation, exopolysaccharides (EPS), dissolved oxygen