Microbial-induced carbonate precipitation (MICP) has the potential to immobilize carbon durably. The carbon source of carbonate minerals is the crucial issue for understanding the fixation mechanism of CO₂ by MICP. However, the carbon source and its temporal changes in microbial-induced carbonate minerals remain little explored. In this study, calcium carbonate (CaCO₃) biomineralization experiments have been carried out using Bacillus cereus in the medium without additional dissolved inorganic carbon (DIC). X-ray diffraction (XRD), attenuated total reflection-infrared spectroscopy (ATR-IR) and scanning electron microscopy (SEM) indicated that the precipitate produced mainly consisted of rhombohedral and irregular calcite. The δ¹³C values of DIC, dissolved organic carbon (DOC), and calcite were the main parameters studied. Carbon isotope fractionation was characterized by carbon isotope offset (Δ¹³C_calcite-DIC or Δ¹³C_{calcite-fluid}). The Δ¹³C_calcite-DIC values ranged from +8.2‰ to +21.5‰, indicating that strain LV-1 induced the accumulation of ¹³C in calcite. The Δ¹³C_{calcite-fluid} values indicated that the calcite was up to +15.0‰ (on average) ¹³C-enriched relative to the fluid. Calculated chemical mass balance data showed that the proportion of CO_2(g) derived from DOC on days 16 and 20 was negative, but it became positive after day 20. Meanwhile, the δ¹³C_CO2(g) value calculated by isotope mass balance was −8.5‰, near to δ¹³C for air (−8.0‰) on day 16, and then shifted to −16.4‰, similar to δ¹³C for tryptone (−17.2‰) after day 20. These results suggested that the amount of CO₂ arising from organic matter through bacterial respiration and the action of enzymes might determine whether the carbon in calcite was derived from organic carbon or atmospheric CO₂. Our findings corroborate the potential utility of MICP for immobilization of CO₂ to reduce net soil CO₂ emissions and to mitigate the greenhouse effect. Microbial-driven carbon isotope fractionation can also cause great carbon isotope shifts in calcite. Thus, carbon isotope value might be used as a marker to identify whether carbonate minerals/rocks are of microbial origin.

微生物诱导的碳酸盐沉淀 (MICP) 具有持久固定碳的潜力。碳酸盐矿物的碳源是理解MICP固定CO _{2机理的关键问题。}然而，碳源及其在微生物引起的碳酸盐矿物中的时间变化仍然很少被探索。在这项研究中，碳酸钙 (CaCO ₃ ) 生物矿化实验已在培养基中使用蜡状芽孢杆菌进行，而无需额外的溶解无机碳 (DIC)。X射线衍射（XRD）、衰减全反射红外光谱（ATR-IR）和扫描电子显微镜（SEM）表明，生成的沉淀主要由菱面体和不规则方解石组成。δ ¹³DIC、溶解有机碳 (DOC) 和方解石的 C 值是研究的主要参数。碳同位素分馏以碳同位素偏移量（Δ ¹³ C_{方解石-DIC}或Δ ¹³ C_{方解石-流体}）为特征。Δ ¹³ C_{方解石-DIC}值范围为+8.2‰至+21.5‰，表明菌株LV-1诱导了方解石中¹³ C的积累。Δ ¹³ C_{方解石-流体}值表明方解石相对于流体的富集程度高达+15.0‰（平均）¹³ C。计算的化学质量平衡数据表明，CO _{2 (g)的比例}16、20天DOC为负值，20天后为正值。同时同位素质量平衡计算的δ ¹³ C _CO2(g)值为-8.5‰，接近空气的δ ¹³ C(-8.0 ‰）在第 16 天，然后转变为 -16.4‰，与第 20 天后胰蛋白胨的 δ ¹³ C（-17.2‰）相似。这些结果表明有机物通过细菌呼吸产生的 CO ₂量和酶可能会确定方解石中的碳是来自有机碳还是来自大气 CO ₂。我们的研究结果证实了 MICP 用于固定 CO ₂以减少净土壤 CO _{2的潜在效用}排放和减轻温室效应。微生物驱动的碳同位素分馏也会导致方解石中的碳同位素发生巨大变化。因此，碳同位素值可用作识别碳酸盐矿物/岩石是否为微生物来源的标志。