Dhami Navdeep K, Alsubhi Walaa R, Watkin Elizabeth, Mukherjee Abhijit
Biologically Activated Materials Laboratory, Department of Civil Engineering, Curtin UniversityPerth, WA, Australia.
School of Biomedical Sciences, Curtin Health Innovation Research Institute-Biosciences, Curtin UniversityPerth, WA, Australia.
Front Microbiol. 2017 Jul 11;8:1267. doi: 10.3389/fmicb.2017.01267. eCollection 2017.
Microbially-induced CaCO precipitation (MICP) is a naturally occurring process wherein durable carbonates are formed as a result of microbial metabolic activities. In recent years, MICP technology has been widely harnessed for applications in civil engineering wherein synthesis of calcium carbonate crystals occurs at ambient temperature paving way for low energy biocement. MICP using pure urease (UA) and carbonic anhydrase (CA) producing bacteria has been promising in laboratory conditions. In the current study we enriched ureolytic and carbonic anhydrase communities in calcareous soil under biostimulation and bioaugmentation conditions and investigated the effect of microbial dynamics on carbonate precipitation, calcium carbonate polymorph selection and consolidation of biological sand column under nutrient limited and rich conditions. All treatments for stimulation and augmentation led to significant changes in the composition of indigenous bacterial population. Biostimulation as well as augmentation through the UA route was found to be faster and more effective compared to the CA route in terms of extracellular enzyme production and carbonate precipitation. Synergistic role of augmented cultures along with indigenous communities was recorded via both the routes of UA and CA as more effective calcification was seen in case of augmentation compared to stimulation. The survival of supplemented isolates in presence of indigenous bacterial communities was confirmed through sequencing of total diversity and it was seen that both UA and CA isolate had the potential to survive along with native communities under high nutrient conditions. Nutrient conditions played significant role in determining calcium carbonate polymorph fate as calcitic crystals dominated under high carbon supplementation. Finally, the consolidation of sand columns via stimulation and augmentation was successfully achieved through both UA and CA route under high nutrient conditions but higher consolidation in short time period was noticed in UA route. The study reports that based upon the organic carbon content in native soils, stimulation can be favored at sites with high organic carbon content while augmentation with repeated injections of nutrients can be applied on poor nutrient soils via different enrichment routes of microbial metabolism.
微生物诱导碳酸钙沉淀（MICP）是一种自然发生的过程，其中由于微生物的代谢活动形成了耐久性碳酸盐。近年来，MICP技术已被广泛应用于土木工程领域，在该领域中碳酸钙晶体在环境温度下合成，为低能耗生物水泥开辟了道路。在实验室条件下，使用产生纯脲酶（UA）和碳酸酐酶（CA）的细菌进行MICP已显示出前景。在本研究中，我们在生物刺激和生物强化条件下，在钙质土壤中富集了尿素分解菌和碳酸酐酶群落，并研究了微生物动态对碳酸盐沉淀、碳酸钙多晶型选择以及在营养有限和丰富条件下生物砂柱固结的影响。所有刺激和强化处理均导致本地细菌种群组成发生显著变化。就细胞外酶产生和碳酸盐沉淀而言，发现生物刺激以及通过UA途径的强化比CA途径更快且更有效。通过UA和CA两条途径都记录了强化培养物与本地群落的协同作用，因为与刺激相比，强化情况下钙化更有效。通过对总多样性进行测序，证实了补充菌株在本地细菌群落存在下的存活情况，并且可以看到UA和CA菌株在高营养条件下都有与本地群落一起存活的潜力。营养条件在决定碳酸钙多晶型的命运方面起着重要作用，因为在高碳补充下以方解石晶体为主。最后，在高营养条件下，通过UA和CA途径成功实现了砂柱的刺激和强化固结，但在短时间内UA途径的固结效果更高。该研究报告称，根据天然土壤中的有机碳含量，在有机碳含量高的地点可以选择刺激，而对于营养贫瘠的土壤，可以通过微生物代谢的不同富集途径，通过重复注入营养物质进行强化。
