Strengthening of sand by calcite producing bacteria Lysinibacillus sp. DRG3 isolated from a naturally cemented site

Saswati Ghatak, Suvendu Manna, Debasis Roy

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Engineering Geology and Rock Mechanics

ABSTRACT: A non-pathogenic soil-residing bacterial strain Lysinibacillus sp. DRG3 was isolated from naturally cemented tailings sand site in eastern India. DRG3 is capable of producing extracellular polymeric substances (EPS) and calcite through ureolytic or non-ureolytic pathways which is rare. The potential of DRG3 in strengthening sand by introducing calcite cementation through ureolytic and non ureolytic process has been investigated in this paper. No report of calcite-precipitating ability of DRG3 or soil strengthening using DRG3 as bio-calcifying agent was found in the literature. In the present study biomass of DRG3 was utilized by growing them in mineral salt media without or with added urea. Observed increases in drained shear strength and dilatancy of water pluviated sand samples, particularly loose, treated with DRG3 from static triaxial test results were found to correlate with the amounts of biogenic EPS and calcite. RÉSUMÉ Un non pathogènes du sol-résidant souche bactérienne Lysinibacillus sp. DRG3 a été isolée de naturellement cimenté sable résidus site en Inde orientale. DRG3 est capable de produire des extracellulaires substances polymériques (EPS) et calcite par ureolytic ou non ureolytic pathways ce qui est rare. Le potentiel de la DRG3 dans le renforcement de sable en introduisant calcite cémentation en caisse par ureolytic et non ureolytic processus a fait l'objet d'une enquête dans ce papier. Aucun rapport de calcite-précipitant capacité des DRG3 ou renforcement des sols utilisant DRG3 comme bio-agent de calcification a été trouvé dans la littérature. Dans la présente étude la biomasse de la DRG3 a été utilisé par leur culture en sels minéraux médias sans ou avec ajout d'urée. Ogoûtez augmente dans vidangée résistance au cisaillement et dilatancy d'eau sable pluviated échantillons, particulièrement lâche, traités avec le système DRG3 de sstatic test triaxial résultats trouvés pour mettre en corrélation avec les montants des EPS biogéniques et calcite. 1 INTRODUCTION Microbes precipitate a variety of cementitious materials, e.g., extracellular polymeric substances (EPS), calcite (CaCO3) and struvite (NH4MgPO4.6H2O). Some species of microorganisms, e.g., Deleya halophila (Rivadeneyra et al. 1991), Chromohalobacter marismortu (Rivadeneyra et al. 2006) and Lysinibacillus sphaericus, Pseudomonas putida (Shirakawa et al. 2011), can produce calcite in the absence of urea. Other species, e.g., Sporosarcina pasteurii and Bacillus megaterium, precipitate calcite only in the presence of urea. These microbes are able to produce urease enzyme which catalyzes the hydrolysis of urea into ammonia and carbon dioxide. Microbes often utilize EPS, high-molecular-weight polymers comprised of mainly sugar residues (polysaccharides), protein, lipid and dead cells, to precipitate cementitious inorganic salts such as calcite or struvite for their nucleation. Although bacteriogenic calcite precipitate has been shown to lead to a measurable increase in the mechanical strength of sand, these studies have so far mainly focused on ureolytic conversion of CO2 into calcite utilizing a strain of Sporosarcina pasteurii (e.g., DeJong et al. 2006; Whiffin et al. 2007; van Paassen et al. 2010; Chou et al. 2011). Unlike the ureolytic bioprocess for calcite production, direct transformation of bacteriogenic CO2 into calcite through non-ureolytic pathways has received scant attention so far. Non-ureolytic calcite production by bacterial species may involve fixation of exhaled CO2 into calcite in the presence of calcium ions (decarboxylation) or nitrogen-containing compounds (deamination followed by decarboxylation). Utility of cementation introduced by microbial EPS has also remained relatively unexplored, possibly because a few reports on this aspect provide ambiguous guidance. Banagan et al. (2010), for instance, reported increased shear strength and liquefaction resistance of loose sand treated with Flavobacterium johnsoniae. Perkins et al. (2000), on the other hand, did not observe a systematic increase in shear strength of sand samples treated with a strain of EPS-producing ultra-microbacteria Klebsiella oxitaca. During a geotechnical and geomicrobiological investigation, strong cementation was noticed within a deposit of hydraulically dumped tailings sand containing no gravel or shell fragments from a placer mining plant on India's east coast (Ghatak et al. 2013). Cementation was found to develop within 1 to 9 years of deposition. Presence of cementitious calcite and struvite minerals within a number of tailings sand samples from layers with high penetration resistance was confirmed from X-ray diffraction data. Microbial population counts within tailings sand samples extracted from within 4 m of ground surface were in approximate agreement with the presence of cementitious calcite and struvite minerals found within the samples. It therefore appeared that the cementation at the tailings sand site was at least, in part, biogenic. The potential of a bacterial species, Lysinibacillus sp. (DRG3), isolated from the tailings sand site in introducing

RÉSUMÉ: gthening of sand by calcite producing bacteria Lysinibacillus sp. DRG3 isolated from a naturally cemented site Saswati Ghatak, Suvendu Manna, Debasis Roy

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Saswati Ghatak; Suvendu Manna; Debasis Roy (2014) Strengthening of sand by calcite producing bacteria Lysinibacillus sp. DRG3 isolated from a naturally cemented site in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper433,author = Saswati Ghatak; Suvendu Manna; Debasis Roy,title = Strengthening of sand by calcite producing bacteria Lysinibacillus sp. DRG3 isolated from a naturally cemented site ,year = 2014}