Pyridoxal kinase PdxY mediated carbon dioxide assimilation to enhance the biomass in Chlamydomonas reinhardtii CC-400.

ABSTRACT

Microalga served as the promising bioresources due to the high efficiency of carbon dioxide conversion. However, the application of microalga is still restricted by low biomass, easier contamination, and high cost of production. To overcome the challenge, engineered Chlamydomonas reinhardtii CC-400 with pyridoxal kinase gene (pdxY) has demonstrated in this study. The results indicated CC-400 with pdxY reached enhanced algal biomass in three different systems, including flask, Two-layer Photo-Reactor (TPR) and airlift Photo-Bioreactor (PBR). The genetic strain PY9 cultured with 1% CO2 in the PBR showed a significant enhancement of biomass up to 1.442 g/L, a 2-times of that of the wild type. We also found the transcriptional levels of carbonic anhydrase (CA) dropped down in PY9 while higher levels of RuBisCo and pdxY occurred, thus the carbon dioxide assimilation under mixotrophic culture dramatically increased. We proofed that pdxY successfully mediated carbon dioxide utilization in CC-400.