This study investigated the effect of co-culturing microalgae with a floc-forming bacterium. Of the six microalgae isolated from a biofloc sample, only Thalassiosira weissflogii, Chlamydomonas sp. and Chlorella vulgaris were propagated successfully in Conway medium. Hence, these species were selected for the experiment comparing microalgae axenic culture and co-culture with the floc-forming bacterium, Bacillus infantis. Results obtained showed that the co-culture had higher microalgae biomass compared to the axenic culture. A similar trend was also observed concerning the lipid content of the microalgae-bacterium co-cultures. The cell number of B. infantis co-cultured with T. weissflogii increased during the exponential stage until the sixth day, but the other microalgae species experienced a significant early reduction in cell density of the bacteria at the exponential stage. This study represents the first attempt at co-culturing microalgae with B. infantis, a floc-forming bacterium, and observed increased biomass growth and lipid accumulation compared to the axenic culture.

Global development of aquaculture industry is getting intensive due to the growing human population that increases food supply and demand, particularly in Asia. Crustaceans and fish are highly valued and also become a profitable aquaculture species due to their fast growth and good market acceptability (Sathiadhas & Najmudeen, 2004). The mud crab, Scylla paramamosain is an important commercial species that are widely distributed in coast of Southern China and Indo-Pacific region (Lin et al., 2017). This