A comprehensive review on carbon source effect of microalgae lipid accumulation for biofuel production

Energy is a major driving force for the economic development. Due to the scarcity of fossil fuels and negative impact on the environment, it is important to develop renewable and sustainable energy sources for humankind. Microalgae as the primary feedstock for biodiesel has shown great application potential. However, lipid yield from microalgae is limited by the upstream cost, which restrain the realization of large-scale biofuel production. The modification of lipid-rich microalgae cell has become the focus over the last few decades to improve the lipid content and productivity of microalgae. Carbon is a vital nutrient that regulates the growth and metabolism of microalgae. Different carbon sources are assimilated by microalgae cells via different pathways. Inorganic carbon sources are mainly used through the CO2-concentrating mechanisms (CCMs), while organic carbon sources are absorbed by microalgae mainly through the Pentose Phosphate (PPP) Pathway and the Embden-MeyerhofPranas (EMP) pathway. Therefore, the addition of carbon source has a significant impact on the production of microalgae biomass and lipid accumulation. In this paper, mechanisms of lipid synthesis and carbon uptake of microalgae were introduced, and the effects of different carbon conditions (types, concentrations, and addition methods) on lipid accumulation in microalgal biomass production and biodiesel production were comprehensively discussed. This review also highlights the recent advances in microalgae lipid cultivation with largescale commercialization and the development prospects of biodiesel production. Current challenges and constructive suggestions are proposed on cost-benefit concerns in large-scale production of microalgae biodiesel. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

Energy is a driving force for economic development, and renewable and sustainable energy sources are important due to the scarcity of fossil fuels and environmental impact. Microalgae, as a primary feedstock for biodiesel, has high application potential, but lipid yield is constrained by high upstream costs. Modifying lipid-rich microalgae cells has been the focus to improve lipid content and productivity. Different carbon sources are assimilated by microalgae through various pathways, impacting biomass and lipid accumulation. This review discusses mechanisms of lipid synthesis, carbon uptake, and the effects of different carbon conditions on lipid accumulation in microalgae biomass and biodiesel production. Recent advances in large-scale commercialization of microalgae lipid cultivation and biodiesel production are highlighted, along with challenges and suggestions for cost-benefit concerns in large-scale production.