Formate for enhancing the growth of microalgae and accumulating high-value products

Formate is the most economical energy and carbon carrier from the reduction of CO2 driven by solar energy, with a good potential in microalgae cultivation. However, the inhibition of formate on the photosynthesis limits its application. Here, using Chlamydomonas reinhardtti as the model, the success of formate enhanced photoautotrophic cultivation was achieved. Guided by the growth and photosynthetic activities, high formate tolerated strains were obtained under the adaptive evolution. While replacing acetate with formate in traditional TAP medium, nearly two third of the biomass productivity was maintained, which performed better than that only with CO2 as carbon source. The maximum utilization efficiency of formate reached 31 % within 48 h, and the content of protein in biomass was also stable than that of TAP group. Preliminary studies on proteomics and methylomics, together with physiological and biochemical, indicated one carbonic anhydrase as a key enzyme responding to formate during cultivation. It's found for the first time that, with the high concentration, over 50 mM, formate caused a global response on cells, such as the repression of cell proliferation, and increase of overall methylation of the genome, which will help the deep understanding of formate metabolism as well as the development of novel methodologies to improve the overall solar energy conversion and carbon fixation efficiency.