Exploiting mixotrophy for improving productivities of biomass and co-products of microalgae

Microalgae biomass as a sustainable feedstock has become an attractive alternative to traditional terrestrial plants for production of renewable chemicals and biofuels. However, achieving high productivity remains as a major challenge in commercial applications. Mixotrophic culture is gaining increasing attention because the metabolic capability of some microalgae to use both photosynthesis and organic carbon leads to higher productivity than either phototrophic or heterotrophic process alone. The potential of mixotrophy for mass algal cultivation should be fully explored. In this review, the superior productivity of mixotrophic cultivation of different algal species was compared with those of phototrophic and heterotrophic culture; The synergism of carbon and energy mechanism of mixotrophic growth was discussed; Particularly, the uniqueness of metabolic regulation of microalgae under mixotrophic culture in terms of carbon recycling and forms of carbon utilized was illustrated; The application in wastewater treatment of mixotrophic culture for uptaking nutrients and organics was discussed. Additionally, the opportunities and challenges of large-scale microalgae production were proposed along with summaries of advancement in various mixotrophic culture technologies. The current literature collectively supports the great potential of mixotrophic culture in enhancing productivities of microalgal biomass and bioproducts with synergy of light and organic carbons metabolism. The findings provide insights for comprehensive understanding the key role of interaction of light and carbons on the enhancement of microalgal biomass and bioproducts under mixotrophic conditions and suggest mixotrophic algal culture should be one of the priority topics for both future research and commercialization efforts.