[论文解读] Influence of on-site low-ureolysis bacteria and high-ureolysis bacteria on the effectiveness of MICP processes

Qinghua Wu, Yuze Wang|arXiv (Cornell University)|Sep 25, 2024

Intensive Care Unit Cognitive Disorders被引用 1

一句话总结

本研究探讨了本地土壤中低脲解活性细菌（OSLUB）和高脲解活性细菌（OSHUB）在与*Sporosarcina pasteurii*联合使用时对微生物诱导碳酸钙沉淀（MICP）效率的影响。OSLUB通过降低pH值，严重抑制*S. pasteurii*的活性和MICP性能，导致抗压强度降低60%；而OSHUB则通过提高pH值，轻微增强活性和强度，使转化率提高9–45%。

ABSTRACT

Microbially Induced Calcium Carbonate Precipitation (MICP) is an eco-friendly technique that enhances soil mechanical properties using urease-producing microorganisms, especially Sporosarcina pasteurii. However, field trials often yield suboptimal results due to the presence of indigenous soil microbes. To evaluate their impact, bacteria from natural soil were classified into two groups: low-ureolysis and high-ureolysis. These were combined with S. pasteurii in experiments using microfluidic chips and sand columns. The analysis covered bacterial populations, urease activity, pH changes, calcium carbonate crystal metrics, and unconfined compressive strength (UCS). Results indicated that mixing low-ureolysis bacteria with S. pasteurii resulted in a 74-84% reduction in bacterial activity and a 60% decrease in chemical conversion rate, leading to a 60% drop in UCS. In contrast, combining high-ureolysis bacteria with S. pasteurii reduced bacterial activity by 49-54%, which was less than the 64% reduction seen with S. pasteurii alone. This combination improved calcium carbonate conversion rates by 9% to 45% and slightly enhanced UCS.The study highlights the distinct effects of low-ureolysis and high-ureolysis bacteria on MICP efficiency, particularly regarding their influence on pH. Low-ureolysis bacteria decrease pH, while high-ureolysis bacteria increase it. Maintaining high bacterial activity and precipitation rates is crucially dependent on pH levels. Future strategies could focus on reducing the presence of low-ureolysis bacteria or sustaining higher pH levels to enhance MICP effectiveness in field applications.

研究动机与目标

• 评估本地土壤细菌在真实现场条件下对MICP效率的影响。
• 对现场低脲解活性细菌（OSLUB）和高脲解活性细菌（OSHUB）在*S. pasteurii*介导的MICP中的作用进行分类与比较。
• 明确本地细菌通过pH调节在决定MICP性能中的作用。
• 提供可操作的策略，通过调控本地微生物群落或控制孔隙液pH值，提升现场规模MICP的效率。

提出的方法

• 利用16S rDNA测序从当地土壤中分离并表征OSLUB和OSHUB。
• 开展批次培养实验，比较120小时内脲酶活性、细菌数量及pH值的变化。
• 进行微流控芯片实验，可视化细菌分布、晶体形态及沉淀动力学。
• 开展砂柱实验，评估碳酸钙沉淀、晶体体积及无侧限抗压强度（UCS）。
• 使用SEM成像分析CaCO3晶体的形貌和粒径分布。
• 应用脲解反应（CO(NH2)2 + 2H2O → 2NH4+ + CO32−）和CaCO3沉淀反应（Ca2+ + CO32− → CaCO3）的方程，建立MICP过程的模型。

实验结果

研究问题

• RQ1 OSLUB和OSHUB在共培养体系中如何影响*S. pasteurii*的脲酶活性和存活率？
• RQ2 当*S. pasteurii*与本地细菌混合时，pH动态在调节MICP性能中起什么作用？
• RQ3 OSLUB和OSHUB如何影响MICP中碳酸钙沉淀速率和晶体特性？
• RQ4 为何在田间试验中MICP性能下降，尽管在实验室条件下*S. pasteurii*表现理想？
• RQ5 通过调控本地细菌群落或pH值，能否提升现场MICP效率？

主要发现

• 将OSLUB与*S. pasteurii*联合培养后，120小时时细菌活性降低74–84%，导致无侧限抗压强度（UCS）相比*S. pasteurii*单独培养降低60%。
• OSHUB共培养使*S. pasteurii*活性仅降低49–54%，显著低于*S. pasteurii*纯培养中64%的下降幅度，表明OSHUB有助于维持活性。
• OSLUB导致共培养体系中pH值逐渐降低，而OSHUB引起pH值升高，直接证明pH调节与MICP效率之间的关联。
• 与*S. pasteurii*对照组相比，OSHUB混合组的碳酸钙化学转化率提高了9–45%，表明沉淀效率得到增强。
• SEM和微流控成像证实，OSLUB混合组产生更少、更大的菱形晶体（>30 μm），而OSHUB混合组形成更小、更密集且分布更均匀的晶体。
• 本研究识别出OSLUB是现场MICP应用中主要的抑制因子，因其导致pH降低和活性抑制；而OSHUB可能作为有益的微生物伙伴发挥作用。