Abstract
ABSTRACTA Serratia sp. expresses a high level of acid phosphatase when grown continuously under carbon limitation. In the presence of CaCl2, biosynthesis of nanocrystalline hydroxyapatite (bio-HA) was achieved by utilizing phosphate released via enzymatic cleavage of an applied substrate (glycerol 2-phosphate: G2P). Hydroxyapatite crystals were identified by energy dispersive X-ray emission (EDX) and selected area diffraction (SAD). X-ray powder diffraction (XRD) analysis gave a mean crystallite size of ∼21–32 nm, with the smallest crystals (21–24 nm) obtained using 1 mM Ca2+ and 1 mM G2P. The uptake of Eu3+ and Sr2+ by bio-HA made by continuously pregrown cells (0.42 mg/mg and 0.043 mg/mg respectively) was ∼20% greater for Sr2+ than was previously reported for bio-HA material of size ∼40 nm made by batch-pregrown cells, while the corresponding uptake of Eu3+ was increased by > 1.8-fold. This was attributed to the localization of Eu (III) at grain boundaries by reference to previous work and highlights the potential of bio-HA as a sequestration agent for recovery of rare earth elements and trivalent actinides.
Highlights
Hydroxyapatite (HA) is a major component of natural bone
Examination by SEM of calcium phosphate-loaded cells shows that, without citrate, the precipitate appeared diffuse (Figure 1A), whereas that made with citrate appeared more dense (Figure 1B)
When cells are challenged with Ca2C and glycerol 2-phosphate (G2P), the biomineralization process relies on the cellular microenvironment becoming supersaturated with inorganic phosphate released from G2P within a structured exocellular space dominated by the extracellular polymeric matrix
Summary
Hydroxyapatite (HA) is a major component of natural bone. Synthetic HA has been used widely in orthopaedics and dentistry (Gabriel et al 2002; Vaz et al 1999), while natural boneHA has been used as a material for sequestering radionuclides (Dimovic et al 2011). By using a natural biofilm a biogenic coating of HA was obtained throughout the matrix of a 3-D structure (Macaskie et al 2005). Use of biofilm yielded a highly adhesive biolayer (Yong et al 2015), which was tightly held on a surface after HA-mineralization (Macaskie et al 2005). Biofilm pre-grown under carbon-limitation was used to make HA (Macaskie et al 2005); since this condition, and the biofilm format of growth, predominate in nature the ability of biofilm-cells to make HA suitable for entrapment of metallic ions was evaluated as the first step towards development of barriers for contaminated water flows
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
