Microbial factors behind struvite precipitation: enzymes and extracellular polymeric substances (EPS) as key players
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Date
2025
Authors
Toprak, P.
Dubey, A.A.
Mukherjee, A.
Pring, A.
Rodriguez-Navarro, C.
Dhami, N.K.
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Journal article
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Applied Microbiology and Biotechnology, 2025; 109(1):266-1-266-21
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Pelina Toprak, Anant Aishwarya Dubey, Abhijit Mukherjee, Allan Pring, Carlos Rodriguez, Navarro, Navdeep K. Dhami
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Abstract
Struvite is a phosphate-based mineral commonly formed in ammonia-rich settings such as soils, aquatic environments, wastewater systems, and the urinary tract. Its distinct morphology and mineral properties have drawn interest across disciplines, including microbiology, geology, medicine, and materials science, especially for its ammonia capturing ability. Microbial metabolic activities have been recently recorded to play a critical role in its formation. However, the influence of microbial characteristics, such as enzymatic activity, biofilm, and extracellular polymeric substances (EPS), on struvite morphology and precipitation mechanisms remains underexplored. This study investigates microbial struvite precipitation mediated by three distinct microbes, Sporosarcina pasteurii, Bacillus subtilis, and Pseudomonas fluorescens to investigate the role of different enzymes and EPS on struvite mineralisation. The bacterial cultures selected for the study have varying ureolytic and alkaline phosphatase activity, as well as EPS and biofilm production potential. Struvite precipitation kinetics under different microbial conditions were studied along with its morphology and biofilm-mineral interactions employing microstructural and mineralogical analyses (via field emission scanning electron microscopy, confocal laser scanning microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy). This study reports that urease and phosphatase activities (between 7 and 7.5 U/mL) along with moderate EPS production (~6.5 g/L), lead to the generation of the highest quantities of struvite crystals with moderate size (~103 ± 5 μm), contrary to the larger crystals (~180 ± 5 μm) produced with a higher urease activity (8.4 U/ mL) and lower EPS (2 g/L). The experimental findings suggest a complex interplay between enzymatic activity and EPS in shaping crystal structure and its features, which have a significant impact on mineral characteristics. Additionally, moderate biofilm formation ( OD570 ~1.2) resulted in maximal struvite precipitation, indicating that structured biofilms support efficient mineral nucleation and accumulation. Overall, this study has unravelled key insights into microbial struvite precipitation mechanisms and can pave the way for tailored engineering and biotechnological applications utilising this phosphate mineral.
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© The Author(s) 2025. This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.