• Journal of Oral Medicine and Pain
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• 제20권1호
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• pp.7-18
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• 1995

The Purpose of this article is to describe the biochemical properties and biological functions of several salivary proteins that possess the unusual properties of inhibiting spontaneous and secondary precipitation of calcium phosphate. This function is very important since human salivary secretion is supersaturated with respect to calcium phosphate. Biological function of statherin, proline rich protein (PRP) and histidine rich protein (HRP) is to inhibit precipitation of calcium phosphate in salivary glands, in the oral fluids, and onto tooth surfaces. The resulting supersaturated state of the salivary secretions contributes a protective and reparative environment which is important for the integrity of the tooth. Beneficial consequences of salivary supersaturation with respect to calcium phosphate are selectively expressed in the oral cavity- that is, protection is provided for the dental enamel-while undesirable consequences, for example, precipitation of calcium phosphates in the salivary glands and onto the teeth do not occur. Purification and structural characteristics of these proteins as well as clinical significance of functions of each protein will be discussed.

• Geomechanics and Engineering
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• 제29권1호
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• pp.79-90
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• 2022

Soybean-urease induced carbonate precipitation (EICP), as an alternative to microbially induced carbonate precipitation (MICP), was employed for soil improvement. Meanwhile, soluble calcium produced from industrial waste carbide slag powder (CSP) via the acid dissolution method was used for the EICP process. The ratio of CSP to the acetic acid solution was optimized to obtain a desirable calcium concentration with an appropriate pH. The calcium solution was then used for the sand columns test, and the engineering properties of the EICP-treated sand, including unconfined compressive strength, permeability, and calcium carbonate content, were evaluated. Results showed that the properties of the biocemented sand using the CSP derived calcium solution were comparable to those using the reagent grade CaCl₂. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed that spherical vaterite crystals were mainly formed when the CSP-derived calcium solution was used. In contrast, spherical calcite crystals were primarily formed as the reagent grade CaCl₂ was used. This study highlighted that it was effective and sustainable to use soluble calcium produced from CSP for the EICP process.

• Journal of Microbiology and Biotechnology
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• 제23권5호
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• pp.707-714
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• 2013

Microbially induced calcium carbonate precipitation (MICCP) is a naturally occurring biological process that has various applications in remediation and restoration of a range of building materials. In the present investigation, five ureolytic bacterial isolates capable of inducing calcium carbonate precipitation were isolated from calcareous soils on the basis of production of urease, carbonic anhydrase, extrapolymeric substances, and biofilm. Bacterial isolates were identified as Bacillus megaterium, B. cereus, B. thuringiensis, B. subtilis, and Lysinibacillus fusiformis based on 16S rRNA analysis. The calcium carbonate polymorphs produced by various bacterial isolates were analyzed by scanning electron microscopy, confocal laser scanning microscopy, X ray diffraction, and Fourier transmission infra red spectroscopy. A strain-specific precipitation of calcium carbonate forms was observed from different bacterial isolates. Based on the type of polymorph precipitated, the technology of MICCP can be applied for remediation of various building materials.

• 한국지반환경공학회 논문집
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• 제13권5호
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• pp.51-57
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• 2012

본 연구에서는 친환경적인 그라우트재의 개발을 위하여 연약지반에 대한 바이오그라우트 가능성을 확인하고, Bacillus Pasteurii 균을 이용하여 탄산칼슘 침전 효과를 분석하였다. 연약지반에 미생물의 탄산칼슘 침전을 이용하여 바이오그라우트에 미치는 영향을 알아보기 위해 4가지 시료의 조건(멸균 시료, 비멸균 시료, 반응용액과 미생물용액의 선처리 혼합시료, 반응용액과 미생물용액의 후처리 혼합시료)으로 실험되었다. 전자현미경(SEM), EDX와 X선 분석 회절기(XRD)를 이용하여 연약지반 시료의 분석을 수행하였고, 이러한 연구결과를 바탕으로 탄산칼슘 침전을 이용한 미생물 처리 공법은 바이오그라우트의 특성을 개선하였다.

• Geomechanics and Engineering
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• 제7권6호
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• pp.649-663
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• 2014

In past few years, the use of bacterial calcium carbonate precipitation (biocementation) has become popular as a ground improvement technique for sandy soil. However, this technique was not applied to organic soil. This study focused on bacterial calcium carbonate precipitation and its effect on permeability in organic soil. A special injection system was prepared for inducing bacterial solution to the samples. The bacterial solution supplied to the samples by gravity for 4 days in specific molds designed for this work. Calcite precipitation was observed by monitoring pH value and measuring amount of calcium carbonate. Change in the permeability was measured before and after biocementation. The test results showed that the pH values indicates that the treatment medium is appropriate for calcite precipitation, and amount of precipitated calcium carbonate in organic soil increased about 20% from untreated one. It was also found that the biocementation can be considered as an effective method for reducing permeability of organic soil. The results were supported by Scanning electron microscopy (SEM) analysis and energy-dispersive x-ray (EDX) analysis.

• 한국결정성장학회지
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• 제30권4호
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• pp.143-149
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• 2020

전복패각을 Ca원으로 이용하여 바이오 소재로 중요한 인산칼슘(calcium phosphates)들을 침전법을 통해 합성하였다. 전복패각에서 유래한 수산화칼슘(Ca(OH)₂)을 칼슘 공급원(전구체)으로 사용하였다. 수용액상에서 수산화칼슘과 인산(H₃PO₄)을 반응시켜 침전반응을 유도하여 인산칼슘화합물로의 합성을 유도하였다. 초기 전구체 Ca/P 비율을 1.50, 1.59 및 1.67로 조절하였으며 이 조성변화와 침전물에 대한 열처리가 분말 및 소결체의 물성에 미치는 영향에 대해 조사하였다. 초기 전구체 Ca/P 비율을 조절함으로써 소결체 상합성의 조절이 가능하였고, 1150℃에서 소결한 소결체에서(hydroxyapatite(HAp), β-tricalcium phosphate(β-TCP) 및 HAp와 β-TCP가 혼합된 2상 인산칼슘(BCP, HA/β-TCP))들이 합성되었다. 이러한 결과는 저비용, 고가용성을 가지는 경제적인 출발물질로부터 고부가가치 인산칼슘을 합성할 수 있는 가능성을 보여주었다.

• 한국결정성장학회지
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• 제22권2호
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• pp.99-104
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• 2012

BCP(biphasic calcium phosphate) 분말을 제조하기 위하여 $Ca(NO_3)_2{\cdot}4H_2O$, $(NH_4)_2HPO_4$를 출발 물질로 공침법(co-precipitation process)을 이용하여 합성하였다. 합성된 분말의 열처리 전 후의 HAp(Hydroxyapatite)/${\beta}$-TCP(${\beta}$-Tricalcium phosphate) 결정상 비율 및 분광학적 특성을 XRD 및 FT-IR를 이용하여 분석하였다. BCP 분말의 생체활성 거동을 평가하기 위하여 Hanks' Balanced Salt Solution(HBSS)에 침적시켜 시간에 따라 형상, 이온농도의 변화 및 결정상을 분석한 결과 낮은 결정화도의 HAp가 생성됨을 확인하였다. BCP분말의 세포독성 평가에서도 대조군에 비하여 세포성장률이 우수함을 관찰하였다.

• KSBB Journal
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• 제21권3호
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• pp.199-203
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• 2006

본 연구에서는 에탄올 농도에 따른 모델용액과 발효액에서 여러 유기산들의 침전거동을 조사하였다. 발효액에서 에탄올의 농도가 높을수록 Ca(LA)2의 침전양이 많았다. Ca(LA)2의 침전효과는 발효액 내에서도 비슷하게 관찰되었다. 모델용액이나 발효액과의 혼합물 대비 30%(v/v)로 에탄올을 첨가하였을 때 젖산분리 공정의 불순물로 존재하는 다른 organic salt들의 침전율도 높았다. 따라서 전체 젖산회수공정의 효율에 대한 연구에서는 에탄올과 발효액의 혼합비율을 20%로 하였다. 반응증류시 일정 온도 이상에서는 젖산회수율이 차이나지 않았다. 에탄올이 첨가된 발효액에서는 대조군과 비교하여 최종젖산 회수율이 38.9% 증가하였다. 또한, 다른 유기산들을 포함한 회수액에서의 순도도 99.7%에 달하였다. 이러한 젖산 회수율의 증가는 owning-out crystallization에 의한 Ca(LA)2의 용해도 감소에 기인한 것으로 판단한다. 본 실험 이후에 더 높은 젖산 회수와 정제 효율을 얻기 위해서는 에탄올의 첨가에 따른 유기산의 거동과, 반응증류에서 사용되는 triethylamine의 양과 반응시간에 대한 검토가 필요할 것으로 사료된다.

• 한국지반공학회논문집
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• 제39권8호
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• pp.7-16
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• 2023

본 연구는 매립지 침출수 내 황산염 농도를 저감하기 위해 친환경 지반개량 공법인 Enzyme Induced Carbonate Precipitation(EICP) 공법을 활용하였다. 황산염의 화학적 침전을 유도하기 위해 충분한 탄산칼슘을 생성함과 동시에 여분의 칼슘 이온을 남길 수 있는 최적의 EICP 혼합비가 계산되었다. 최적 혼합비로 처리된 사질토 시편에서 황산염 침전이 전단 강성도에 미치는 영향을 확인하고자 전단파 속도를 측정하였고 전단파 속도 측정은 EICP 반응 및 황산염 반응 시간동안 수행되었다. 실험 결과, 생성된 침전물에 따른 전단 강성도의 발달을 확인하였고 주사전자현미경(SEM)으로 침전물의 유형 및 패턴을 시각적으로 관찰하였다. 고순도 우레아제의 대체제로서 백태가루를 효소로 사용한 EICP 용액의 경우 고순도 EICP 용액과 동일한 탄산칼슘 생성 효율에서 보다 낮은 황산염 제거 효율을 보였는데 이는 백태가루에 포함된 불순물이 석고의 침전을 방해하기 때문이다.

• Journal of Periodontal and Implant Science
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• 제30권1호
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• pp.187-203
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• 2000

The precipitation of calcium phosphate on implant surface has been known to accelerate osseointegration and to enhance osseous adaptation. The present study was performed to examine whether the precipitation of calcium phosphate on Ti-6Al-4V alloy could be affected by the immersion in NaOH solution and heat treatment. Ti-6Al-4V alloy plates of $15{\times}3.5{\times}1mm$ in dimension were polished sequentially from #240 to #2,000 emery paper and one surface of each specimen was additionally polished with $0.1{\mu}m$ alumina paste. Polished specimens were soaked in various concentrations of NaOH solution(0.1, 1.0, 3.0, 5.0, 7.0, 10.0 M) at $60^{\circ}C$ for 24 hours for alkali treatment, and 5.0 M NaOH treated specimens were heated for 1 hour at each temperature of 400, 500, 600, 700, $800^{\circ}C$. After the alkali and heat treatments, specimens were soaked in the Hank's solution with pH 7.4 at $36.5^{\circ}C$ for 30days.The surface ingredient change of Ti-6Al-4V alloy was evaluated by thin-film X-ray diffractometer(TF-XRD) and the surface microstructure was observed by scanning electron microscope(SEM), and the elements of surface were analyzed by X-ray photoelectron spectroscopy(XPS). The results were obtained as follows ; 1. The precipitation of calcium phosphate on Ti-6Al-4V alloy was accelerated by the immersion in NaOH solution and heat treatment. 2. In Alkali treatment for the precipitation of calcium phosphate on Ti-6Al-4V alloy, the optimal concentration of NaOH solution was 5.0 M. 3. In heat treatment after alkali treatment in 5.0 M NaOH solution, the crystal formation on alloy surface was enhanced by increasing temperature. In heat treated alloys at $600^{\circ}C$, latticed structure and prominences of calcium phosphate layer were most dense. On heat treated alloy surface at the higher temperature(${\geq}700^{\circ}C$), main crystal form was titanium oxide rather than apatite. The above results suggested that the precipitation of calcium phosphate on the surface of Ti-6Al-4V alloy could be induced by alkali treatment in 5.0 M-NaOH solution and by heat treatment at $600^{\circ}C$.