Co-cultivation of Euglena gracilis and Pseudoalteromonas sp. MEBiC 03607 for paramylon production

Depending on the culture conditions, Euglena gracilis can produce a variety of macromolecules such as vitamins, lipids, proteins, and polysaccharides. In particular, the ability of E. gracilis to store a lot of β-glucans implies it has significant biotechnological potential. In this study, the growth of E. gracilis and its paramylon content were improved through co-cultivation with the bacterium Pseudoalteromonas sp. MEBiC 03607. To determine the optimal co-cultivation strategy, the effects of the algae-to-bacterial inoculum ratio and growth stage of E. gracilis were examined. Under optimal conditions, the growth of E. gracilis and its paramylon content were increased by more than 17 and 25%, respectively, as a direct result of the cultivation with bacteria. Through qRT-PCR analysis, it was confirmed that when the bacteria were inoculated, the expression of gene related to β-glucan synthase was increased, while the expression of wax ester synthase-related gene was decreased. This indicates that bacteria promote the synthesis of β-glucans of E. gracilis and inhibit the conversion of β-glucan to wax ester. These results demonstrate a novel approach to improve the growth of E. gracilis and its paramylon productivity.