Increased cellulose production by heterologous expression of cellulose synthase genes in a filamentous heterocystous cyanobacterium with a modification in photosynthesis performance and growth ability

Cellulose and sugar from microalgae can be utilized for the production of biofuel ethanol. Increasing cellulose and sugar synthesis capacity is key for high yield production of this biofuel. To enhance cellulose production, we transferred acsAB, responsible for cellulose synthesis in bacterium Acetobacter xylinum, into the cyanobacterium, Anabaena sp. strain PCC7120, by conjugation. PCR confirmed the presence of acsAB in Anabaena sp. strain PCC7120 exconjugates. RT-PCR demonstrated the up-regulation of acsAB expression. Production of extracellular cellulose secreted from Anabaena sp. strain PCC7120 carrying acsAB was revealed using Calcofluor white staining and cellobiohydrolase I (CBHI)-FITC labeling. Further evidence obtained from the digestion of cellulose to glucose demonstrated that the amount of glucose released from cellulose was significantly increased in Anabaena sp. PCC7120 cells carrying acsAB as compared to the wild type. The photosynthetic efficiency and growth rate were increased in the transgenic strains. Cellulose synthesis is thus enhanced in Anabaena sp. strain PCC7120 expressing acsAB and does not negatively impact photosynthesis and growth.