Microalgal co-cultures for biomanufacturing applications.

High demands in consumer goods and pressures from governments to meet environmental regulations have pushed industries to find innovative, carbon-neutral solutions. Sustainable methods in biotechnology are sought to increase productivity whilst keeping at bay one of the major problems in monoculture production routes: contamination. The use of engineered consortia is seen as a viable option. In nature, microorganisms exist as part of complicated networks known as consortia. Within the consortia, each member plays a role in facilitating communication, tasks distribution, nutrients acquisition and protection. This emerging field uses the conundrums that govern natural microbial assemblages to create artificial co-culture within the laboratory. Purpose fit, co-cultures have been created, to enhance productivity yields of desired products, for bioremediation and to circumvent contamination.

The use of microalgae in co-cultures is the focus of this study. Microalgae have application in many fields and are ideal candidates for bioproduction and carbon sequestration. The results of two different systems are presented, which aim to increase the productivity of microalgae biomass and of β-carotene or lipids. The natural consortium of Dunaliella salina, Halomonas and Halobacterium salinarum showed both an increase in microalgae cell concentration by 79% and higher β-carotene productivity compared to the monoculture. This association also showed that Halomonas is able to aid D. salina when subjected to abiotic stress. The artificial co-culture of Scenedesmus obliquus and Rhodosporidium toruloides showed an increase in microalgae biomass by 20%; however, the FAME levels of 26% dw were not a significant increase, compared to monocultures. Both systems demonstrated that if one member of the assemblage is in dire stress, this stress will translate to the entire community. Characterisation of exopolymeric substances and metabolites provided a fuller picture on how these microorganisms co-exist. Additionally, a novel method, duo-plates, was developed and successfully tested to trap metabolites within co-cultures.