典型化能自养细菌固碳潜能解析及其激发策略研究

Microbial carbon fixation is of great significance to CO2 emission reduction and resource utilization. Compared with microalgae, chemoautotrophic bacteria have the advantage of fixing CO2 in dark environments such as soils and large scale reactor. However, their growth rate is generally slow, and the apparent carbon fixation efficiency (refer to the sum of extracellular free organic carbon and intracellular organic carbon) is also low. Moreover, the extracellular free organic carbon which has been fixed by chemoautotrophic bacteria has a significant negative feedback on the autotrophic process. Thus, it is difficult to judge a bacterium’s carbon fixation potential and to explore the bacteria with high carbon fixation potential just depending on the actual apparent carbon fixation efficiency. In addition, for the bacteria with high carbon fixation potential, there are few reports about how to eliminate the feedback of extracellular organic carbon on their autotrophic process and thus inspire their carbon fixation potential. It has been appreciated that the intrinsic factors to decide the autotrophic bacteria carbon fixation potential are the key CO2 fixation enzyme gene expression potential and the enzyme specific activity, as well as the ribosomal RNA gene copy number and protein synthesis efficiency per unit of ribosomal RNA. Therefore, in order to provide theoretical guidance and technical support for improving the apparent carbon fixation efficiency of chemoautotrophic bacteria, the differences of CO2 fixation potential among different species of chemoautotrophic bacteria will be analyzed, and the major intrinsic determinant of carbon fixation potential will be clarified from the levels of genes and their transcription combined with protein analysis. Based on above, the high CO2 fixation potential species will be excavated, and the technologies to eliminate the free organic carbon inhibition effect based on microbial symbiosis and membrane separation technology will be developed.

微生物固碳对于CO2减排与资源化意义重大。相比微藻，化能自养细菌具有可在土壤与大型反应器等无光环境中固碳的优势。但其生长较慢，表观固碳效率（指胞外游离的和增殖细胞内有机碳的总和）较低，且固定的游离有机碳对其自养过程有显著负反馈，因而仅从实际表观固碳效率很难判断某菌的固碳潜能，从而难以发掘出高固碳潜能菌。此外，对于高固碳潜能菌，如何消除固定的游离有机碳对其自养过程的负反馈，激发其固碳潜能，也未见有报道。关键固碳酶的基因表达潜能与比活性、rRNA基因拷贝数和单位核糖体蛋白质合成效率是影响化能自养细菌固碳潜能的内在因素。因此，从基因及其转录水平入手，结合蛋白质分析，解析各类化能自养细菌固碳潜能的种间差异，阐明最主要的固碳潜能决定因素，进而发掘出具有高固碳潜能的菌，并在此基础上研发基于微生物互养共生与膜分离的游离有机碳抑制效应消减技术，将为大幅提高化能自养细菌的表观固碳效率提供理论指导与技术支撑。

微生物固碳对于CO2减排与资源化意义重大。化能自养细菌具有可在土壤与大型反应器等无光环境中固碳的优势。但其生长较慢，表观固碳效率较低，且固定的游离有机碳（EFOC）对其自养过程有显著负反馈，因此仅从实际表观固碳效率很难判断某菌的固碳潜能，难以发掘出高固碳潜能菌。此外，如何消除固定的游离有机碳对其自养过程的负反馈，也未见有报道。本研究从基因及其转录水平入手，结合蛋白质分析，解析了各类化能自养细菌固碳潜能的种间差异，阐明了最主要的固碳潜能决定因素并发掘出了具有高固碳潜能的自养菌，并在此基础上研发了基于微生物互养共生与膜反应器的胞外有机物抑制效应消减技术。结果表明，氢氧化细菌和硫氧化细菌(SOB)的表观固碳量和固碳速率在其自养培养过程中都呈现显著的种间差异性，某一种单菌培养过程中表观固碳速率的变化与cbb基因转录效率的变化相关。不同菌种的表观固碳效率的差异性主要归因于cbb基因转录及rRNA基因拷贝数之间的相互作用。不同类型自养菌其不同的EFOC/TOC比例主要由cbb基因转录效率和细胞骨架合成速率决定，EFOC/TOC的比例越低，其表观固碳效率就越高；能量供给充足可降低EFOC/TOC比值，有利于细胞的自养生长。小分子EFOC显著抑制cbb基因转录，降低固碳速率，因此是主要的抑制因子。所选取的SOB中DSM 505具有最高的蛋白质合成潜能和最高的CO2同化潜能，因此是具有较高表观固碳潜能的SOB。利用异养菌枯草杆菌与两种硫氧化细菌成功构建了异养-自养共生系统，显著激发了自养微生物的固碳潜能。膜生物反应器可分离出反应器内EFOC，同时富集细菌在反应器内，消解了EFOC对cbb基因转录及细菌生长的抑制，大幅提高了化能自养细菌的固碳能力。研究结果将为大幅提高化能自养细菌的表观固碳效率提供理论指导与技术支撑。