Tong Sheng, Zhao Lizhi, Zhu Daling, Chen Wuxi, Chen Limei, Li Demao
Tianjin Key Laboratory for Industrial Biological Systems and Bioprocessing Engineering, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, China.
National Innovation Centre for Synthetic Biology, Tianjin, 300308, China.
Bioresour Bioprocess. 2022 May 18;9(1):55. doi: 10.1186/s40643-022-00544-0.
With the increase in population growth and environmental pollution, the daily protein supply is facing great challenges. Single-cell protein (SCP) produced by microorganism fermentation is a good alternative for substituting plant- and animal-derived proteins. In this study, Paracoccus communis MA5 isolated from soil previously demonstrated an excellent ability to synthesize SCP directly from sodium formate. To investigate the central metabolic network of formic acid assimilation and protein synthesis, genome-scale analyses were performed. Genomic analysis showed that complete tetrahydrofolate cycle-, serine cycle-, glycolytic pathway-, tricarboxylic acid (TCA) cycle- and nitrogen metabolism-relevant genes were annotated in the genome. These pathways play key roles in the conversion of formic acid into proteins. Transcriptional analysis showed that sodium formate stress could stimulate the metabolic pathway in response to environmental stress, but weaken the sulfur metabolic pathway to inhibit amino acid synthesis, resulting in a decrease in protein content (30% vs 44%). However, under culture conditions with ammonium sulfate, metabolic pathways associated with protein synthesis were accelerated, causing an increase in protein content (53% vs 44%); while the tetrahydrofolate cycle associated with formic acid assimilation was inhibited, causing a 62.5% decrease in growth rate (OD: 0.21 vs 0.56). These results provide evidence of protein synthesis from sodium formate in strain MA5 at the gene level and lay a theoretical foundation for the optimization of fermentation systems using formic acid as a carbon source.
随着人口增长和环境污染的加剧，日常蛋白质供应面临着巨大挑战。微生物发酵产生的单细胞蛋白（SCP）是替代植物源和动物源蛋白的良好选择。在本研究中，先前从土壤中分离出的共栖副球菌MA5表现出从甲酸钠直接合成SCP的卓越能力。为了研究甲酸同化和蛋白质合成的中心代谢网络，进行了基因组规模分析。基因组分析表明，基因组中注释了完整的四氢叶酸循环、丝氨酸循环、糖酵解途径、三羧酸（TCA）循环和氮代谢相关基因。这些途径在甲酸转化为蛋白质的过程中起关键作用。转录分析表明，甲酸钠胁迫可刺激响应环境胁迫的代谢途径，但会削弱硫代谢途径以抑制氨基酸合成，导致蛋白质含量下降（30%对44%）。然而，在硫酸铵培养条件下，与蛋白质合成相关的代谢途径加速，导致蛋白质含量增加（53%对44%）；而与甲酸同化相关的四氢叶酸循环受到抑制，导致生长速率下降62.5%（OD：0.21对0.56）。这些结果在基因水平上为菌株MA5中甲酸钠合成蛋白质提供了证据，并为优化以甲酸为碳源的发酵系统奠定了理论基础。
