Isolation and Characterization of -Associated Bacteria, sp. CA3 and sp. CN5, Capable of Promoting the Growth and Paramylon Production of under Mixotrophic Cultivation.

produces paramylon, which is a feedstock for high-value functional foods and nutritional supplements. The enhancement of paramylon productivity is a critical challenge. Microalgae growth-promoting bacteria (MGPB) can improve microalgal productivity; however, the MGPB for remain unclear. This study isolated bacteria capable of enhancing growth and paramylon production under mixotrophic conditions. sp. CA3 and sp. CN5 were isolated from grown with sewage-effluent bacteria under mixotrophic conditions at pH 4.5 or 7.5, respectively. In a 7-day mixotrophic culture with glucose, CA3 increased biomass and paramylon production 1.8-fold and 3.5-fold, respectively (at pH 4.5), or 1.9-fold and 3.5-fold, respectively (at pH 7.5). CN5 increased biomass and paramylon production 2.0-fold and 4.1-fold, respectively (at pH 7.5). However, the strains did not show such effects on under autotrophic conditions without glucose. The results suggest that CA3 and CN5 promoted both growth and paramylon production under mixotrophic conditions with glucose at pH 4.5 and 7.5 (CA3) or pH 7.5 (CN5). This study also provides an isolation method for MGPB that enables the construction of an effective -MGPB-association system for increasing the paramylon yield of