巴氏芽孢杆菌固化污染土的培养优化与矿化机制

Optimization of Sporosarcina pasteurii Culture and Mineralization for Soil Solidification

摘要:

微生物诱导碳酸钙沉淀（MICP）作为生态友好、可持续的污染土固化技术，关键在于能高效产脲酶的微生物。通过菌液配制以及微生物优化培养试验，研究了振荡转速、温度、培养基pH值等培养条件对巴氏芽孢杆菌生长及脲酶活性的影响规律，并结合傅里叶变换红外光谱、X射线光电子能谱、X射线衍射和扫描电镜等方法分析了生物矿化沉淀的生成机制。结果表明，210 r·min^-1下振荡转速培养基溶氧量高，细菌浓度及脲酶活性也较高；初始接种量为0.5%时培养基营养物质得到充分利用，细菌增殖速度快；30 ℃为细菌最佳生长环境温度；细菌耐受pH值范围为5~10，偏酸性环境能延缓脲酶活性达到峰值的时间，偏碱性环境更有利于激发脲酶活性；尿素质量浓度为5~25 g·L^-1时细菌生长速率较快，脲酶活性高。MICP过程在细菌的胞外聚合物上进行，生成的碳酸钙主要由菱形方解石和少量球形球霰石组成。

Abstract:

The microbial-induced calcite precipitation （MICP） method represents an ecologically friendly and sustainable microbial treatment and remediation technology designed for soil solidification and contamination， and the efficacy of the method depends on the microorganism adept at urease production. A comprehensive investigation was conducted to study the impacts of factors such as oscillating speed， temperature， medium pH on the growth and urease activity of Sporosarcina pasteurii. The underlying mechanisms of biomineralization precipitation were revealed by synergistically utilizing techniques such as Fourier transformation infrared spectroscopy， X-ray photoelectron spectroscopy， X-ray diffraction，and scanning electron microscopy. The findings unequivocally demonstrate that an oscillating speed of 210 r·min^-1 coincides with heightened levels of dissolved oxygen within the medium， thereby fostering elevated bacterial concentrations and augmented urease activity. The judicious utilization of an initial inoculum quantity amounting to 0.5% of the medium constituents engenders maximal nutrient consumption and precipitates rapid bacterial proliferation. A temperature of 30 ℃ is established as the ideal for fostering bacterial growth， striking a balance between avoiding dormancy due to lower temperatures and evading protein denaturation and inactivation attributed to excessive heat. The bacterial consortia exhibit a notable resilience across a pH spectrum spanning 5 to 10， with acidic conditions eliciting a prolonged interval for urease activity to attain its zenith. Despite this delay， the pinnacle of urease activity remains relatively unaltered， whereas an alkaline milieu is conducive to accentuating urease activity. Urea， as a pivotal determinant， exerts a direct influence on the adenosine triphosphate （ATP） synthesis， which is crucial for bacterial energy metabolism， and thus profoundly affecting both bacterial proliferation and urease activity. Notably， a urea concentration ranging from 5 to 25 g·L^-1 fosters expedited bacterial growth rates coupled with heightened urease activity. The MICP process was carried out on extracellular polymers of bacteria， and the generated calcium carbonate was mainly composed of rhombic calcite and a small amount of spherical vaterite.