A Low-Tech Bioreactor System for the Enrichment and Production of Ureolytic Microbes

Enhanced MICP for Soil Improvement and Heavy Metal Remediation: Insights from Landfill Leachate-Derived Ureolytic Bacterial Consortium

This study investigates the potential of microbial-induced calcium carbonate precipitation (MICP) for soil stabilization and heavy metal immobilization, utilizing landfill leachate-derived ureolytic consortium. Experimental conditions identified yeast extract-based media as most effective for bacterial growth, urease activity, and calcite formation compared to nutrient broth and brown sugar media. Optimal MICP conditions, at pH 8-9 and 30 °C, supported the most efficient biomineralization. The process facilitated the removal of Cd2+ (99.10%) and Ni2+ (78.33%) while producing stable calcite crystals that enhanced soil strength. Thermal analyses (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)) confirmed the successful production of CaCO3 and its role in improving soil stability. DSC analysis revealed endothermic and exothermic peaks, including a significant exothermic peak at 444 °C, corresponding to the thermal decomposition of CaCO3 into CO2 and CaO, confirming calcite formation. TGA results showed steady weight loss, consistent with the breakdown of CaCO3, supporting the formation of stable carbonates. The MICP treatment significantly increased soil strength, with the highest surface strength observed at 440 psi, correlating with the highest CaCO3 content (18.83%). These findings underscore the effectiveness of MICP in soil stabilization, pollutant removal, and improving geotechnical properties.

Application of urease-producing microbial community in seawater to dust suppression in desert

In order to solve the dust problem caused by sandstorms, this paper aims to propose a new method of enriching urease-producing microbial communities in seawater in a non-sterile environment. Besides, the difference of dust suppression performance of enriched microorganisms under different pH conditions was also explored to adapt the dust. The Fourier-transform infrared spectrometry (FTIR) and Scanning electron microscopy (SEM) confirmed the formation of CaCO₃. The X-ray diffraction (XRD) further showed that the crystal forms of CaCO₃ were calcite and vaterite. When urease activity was equivalent, the alkaline environment was conducive to the transformation of CaCO₃ to more stable calcite. The mineralization rate at pH = 10 reached the maximum value on the 7^th day, which was 97.49 ± 1.73%. Moreover, microbial community analysis results showed that the relative abundance of microbial community structure was different under different pH enrichment. Besides, the relative abundance of Sporosarcina, a representative genus of urease-producing microbial community, increased with the increase of pH under culture conditions, which consistent with the mineralization performance results. In addition, the genus level species network diagram also showed that in the microbial community, Sporosarcina was negatively correlated with another urease-producing genus Bacillus, and had a reciprocal relationship with Atopostipes, which means that the urease-producing microbial community was structurally stable. The enrichment of urease-producing microbial communities in seawater will provide empirical support for the large-scale engineering application of MICP technology in preventing and controlling sandstorms in deserts.

Bioanalytical insight into the life of microbial populations: A chemical monitoring of ureolytic bacteria growth

In this publication an alternative approach to investigations of bacterial growth is proposed. Contrary to the conventional physical methods it is based on enzyme activity detection. The procedure for real-time and on-line monitoring of microbial ureolytic activity (applied as a model experimental biosystem) in the flow analysis format is presented. The developed fully-mechanized bioanalytical flow system is composed of solenoid micropumps and microvalves actuated by Arduino microcontroller. The photometric detection based on Nessler reaction is performed using dedicated flow-through optoelectronic detector made of paired light emitting diodes. The developed bioanalytical system allows discrete assaying of microbial urease in the wide range of activity up to 5.4 U mL^-1 with detection limit below 0.44 U mL^-1, a high sensitivity in the linear range of response (up to 200 mV U^-1 mL and relatively high throughput (9 detection per hour). The proposed differential procedure of measurements (i.e. a difference between peaks register for sample with and without external addition of urea is treated as an analytical signal) allows elimination of interfering effects from substrate and products of biocatalysed reaction as well as other components of medium used for microbial growth. The developed bioanalytical system was successfully applied for the control of growth of urease-positive bacteria strains (Proteus vulgaris, Klebsiella pneumoniae and Paracoccus yeei) including examination of effects from various microbial cultivation conditions like temperature, composition of culture medium and amount of substrate required for induction of bacterial enzymatic activity. The developed bioanalytical flow system can be applied for metabolic activity-based estimation of parameters of lag and log phases of microbial growth as well as for detection of decline phase.