AUTHOR=Zhu Zhen , Cao Huijiao , Li Xu , Rong Junfeng , Cao Xupeng , Tian Jing TITLE=A Carbon Fixation Enhanced Chlamydomonas reinhardtii Strain for Achieving the Double-Win Between Growth and Biofuel Production Under Non-stressed Conditions JOURNAL=Frontiers in Bioengineering and Biotechnology VOLUME=8 YEAR=2021 URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2020.603513 DOI=10.3389/fbioe.2020.603513 ISSN=2296-4185 ABSTRACT=

The stressed cultivations are widely used in microalgae R&D for the biofuel production with the repress on growth to a certain degree, which limits the overall productivity. The balance between the growth and energy storage compounds accumulation is a target needing the combination of both strain selection or construction and culture optimization. Here, an engineered strain of Chlamydomonas reinhardtii, in which the chloroplast type glyceraldehyde-3-phosphate dehydrogenase (cGAPDH) was overexpressed and named as P3-GAPDH, was cultured on the Algal Station platform. Compared with wild type (WT), C. reinhardtii CC137c, in Tris-acetate-phosphate (TAP) medium, the highest density of WT and P3-GAPDH were 1.23 ± 0.13 and 1.74 ± 0.09 g L^–1 within 96 h, and the maximum biomass productivity was 24.30 ± 1.65 and 28.54 ± 1.43 mg L^–1 h^–1, respectively. In terms of the energy storage compounds, both carbohydrate and fatty acids content doubled in P3-GAPDH, from 0.13 ± 0.02 to 0.26 ± 0.04 g L^–1 for carbohydrate and from 0.08 ± 0.01 to 0.16 ± 0.01 g L^–1 for fatty acids, among which poly unsaturated fatty acids increased by 65.8%. Together with the continuous monitor of the chlorophyll fluorescence dynamics parameters F_v/F_m and F_v’/F_m’ and pH of culture, enhanced Calvin cycle by overexpressed cGAPDH promoted the carbon conversion and subsequent energy storage compounds accumulation. C. reinhardtii P3-GAPDH strain showed the potential as a good chassis with high carbon conversion ability.