Ethanol production with starch-based Tetraselmis subcordiformis grown with CO 2 produced during ethanol fermentation

A system coupling ethanol fermentation with microalgae culture was developed, in which CO₂ produced during ethanol fermentation was used as carbon source for the growth of Tetraselmis subcordiformis, a microalgae accumulating starch intracellularly. The biomass concentration about 2.0 g DCW/L was achieved within the photobioreactor for the batch culture of 7 days, and intracellular starch accumulation was about 45%. Furthermore, ultrasonic pretreatment and enzymatic hydrolysis were applied to the microalgae biomass, and 71.1% of the intracellular starch was converted into glucose that was fermented sequentially to ethanol by Saccharomyces cerevisiae with an ethanol yield of 87.6% of the theoretical value, indicating that the microalgae biomass could be an alternative feedstock for ethanol production to save grain consumption, and in the meantime mitigate the CO₂ emission.