• Geomechanics and Engineering
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• 제17권5호
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• pp.445-452
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• 2019

Gel-type biopolymers have recently been introduced as environmentally friendly soil binders and have shown substantial strengthening effects in laboratory experimental programs. Although the strengthening effects of biopolymer-treated sands have been verified in previous direct shear tests and uniaxial compression tests, there has been no attempt to examine shear behavior under different confining stress conditions. This study therefore aimed to investigate the strengthening effects of biopolymer-treated sand using laboratory triaxial testing with a focus on confining pressures. Three representative confining pressure conditions (${\sigma}_3=50kPa$, 100 kPa, and 200 kPa) were tested with varying biopolymer contents ($m_{bp}/m_s$) of 0.5%, 1.0%, and 2.0%, respectively. Based on previous studies, it was assumed that biopolymer-treated sand is susceptible to hydraulic conditions, and therefore, the experiments were conducted in both a hydrated xanthan gum condition and a dehydrated xanthan gum condition. The results indicated that the shear resistance was substantially enhanced and there was a demonstrable increase in cohesion as well as the friction angle when the biopolymer film matrix was comprehensively developed. Accordingly, it can be concluded that the feasibility of the biopolymer treatment will remain valid under the confining pressure conditions used in this study because the resisting force of the biopolymer-treated soil was higher than that in the untreated condition, regardless of the confining pressure.

• Geomechanics and Engineering
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• 제12권5호
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• pp.785-801
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• 2017

Biopolymer treatment of geomaterials to develop sustainable geotechnical systems is an important step towards the reduction of global warming. The cutting edge technology of biopolymer treatment is not only environment friendly but also has widespread application. This paper presents the strength and slake durability characteristics of biopolymer-treated sand sampled from Al-Sharqia Desert in Oman. The specimens were prepared by mixing sand at various proportions by weight of xanthan gum biopolymer. To make a comparison with conventional methods of ground improvement, cement treated sand specimens were also prepared. To demonstrate the effects of wetting and drying, standard slake durability tests were also conducted on the specimens. According to the results of strength tests, xanthan gum treatment increased the unconfined strength of sand, similar to the strengthening effect of mixing cement in sand. The slake durability test results indicated that the resistance of biopolymer-treated sand to disintegration upon interaction with water is stronger than that of cement treated sand. The percentage of xanthan gum to treat sand is proposed as 2-3% for optimal performance in terms of strength and durability. SEM analysis of biopolymer-treated sand specimens also confirms that the sand particles are linked through the biopolymer, which has increased shear resistance and durability. Results of this study imply xanthan gum biopolymer treatment as an eco-friendly technique to improve the mechanical properties of desert sand. However, the strengthening effect due to the biopolymer treatment of sand can be weakened upon interaction with water.

• Journal of Microbiology and Biotechnology
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• 제15권3호
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• pp.626-632
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• 2005

A new bacterium BL-2 excreting a novel cationic polyglucosamine biopolymer was isolated from the spoiled leaves of Chinese cabbage and identified as Enterobacter sp. BL-2. The isolated Enterobacter sp. BL-2 was cultivated in pH-stat fed-batch culture using acetic acid as the feeding stock at pH 8.0, resulting in 17.11 g/l of cells and 1.53 g/l of an extracellular biopolymer after 72 h. The excreted biopolymer was purified by a three-step procedure, involving ethanol precipitation and deproteinizations, to a nearly homogeneous state, and its molecular weight was found to be 106 kDa. It was composed of glucosamine, rhamnose, and galactose at a molar ratio of 86.4:1.6:1.0, respectively, indicating a rarely found novel high-glucosamine-containing biopolymer. The FT-IR and $^{13}C-NMR$ spectra of the novel cationic polyglucosamine biopolymer PGB-l revealed a close identity with chitosan from crab shell. It can effectively flocculate various suspended solids, including kaolin clay, $Ca(OH)_2,\;Al_{2}O_3$, active carbon, microbial cells, and acidic dyes.

• 한국미생물·생명공학회지
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• 제17권4호
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• pp.397-402
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• 1989

Methylobacterium organophilum 이 탄소원과 에너지원으로서 메탄올로부터 생성하는 새로운 다당류계 생물고분자의 화학적 성질과 물성학적 성질을 관찰하였다. 분리정제한 다당류의 분자량은 약 4-5$\times$$10^6$ dalton 정도로 고분자량을 지니고 있다. 다당류의 화학적 조성은 건조중량의 66%가 탄수화물로 구성되어 있으며 이들의 88%가 환원당으로 구성되어 있다. 특이하게 본 고분자는 건조중량의 4.7%가 단백질로 구성되어 있다. 다당류는 glucose, galactose, 그리고 mannose을 몰비로 2:3:2 함유하고 있으며 탄수화물 이외에도 pyruvic acid, uronic acid, acetic acid 등을 함유하고 있다. 정제된 다당류를 증류수에 용해시켜 농도별로 점도를 측정한 결과 비뉴톤성 성질 중 pseudoplastic 성질을 보였으며 농도가 증가함에 따라서 겉보기점도 증가가 월등히 높았다. 동일한 1% 용액의 경우 K(consistency index)값을 비교하면 xanthan gum에 비해 약 10배정도 높은 18,000 cp 값을 나타내었다.

• 한국미생물·생명공학회지
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• 제24권1호
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• pp.111-118
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• 1996

For the screening and the development of the new bio-material, cultural conditions for the exo-biopolymer (EBP) production throught the submerged cultivation of Ganoderma lucidum mycelium were investigated. Also, the fractionations and the purifications of the exo-biopolymer were carried out and the chemical compositions of the exo-biopolymer were examined. The optimal culture conditions for the exo-biopolymer production were pH 5.0, 30$^{\circ}C$ and 100 rpm of agitation speed in the medium containing of 5% (w/v) glucose, 0.5%(w/v) yeast extract, 0.1% (w/v) ($(NH_4)_2HPO_4$, and 0.05% (w/v) $KH_2PO_4$. In the flask cultivation for 7 days under these conditions, the concentration of the maximum exo-biopolymer and the cell mass were 15.4g/l and 18.8g/l, respectively. The specific growth rate was 0.039 $hr^{-1}$. In addition, the substrate consumption rate, and the exo-biopolymer production rate were 0.043$gg^{-1}$$hr^{-1}$ and 0.025$gg^{-1}$$hr^{-1}$, respectively. The exo-biopolymer was fractionated into BWS (water soluble exo-biopolymer) and BWI (water insoluble exo-biopolymer) by the water extraction, and the sugar contents of two fractions were higher than 97% (based on dry basis). The components sugar of BWS and BWI fractions were glucose, galactose, mannose, xylose, and fucose. Their molar ratios were 3.6:1.5:2.1:0.5: trace and 2.9:3.1:2.0:1.6:0.3, respectively.

• Geomechanics and Engineering
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• 제29권5호
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• pp.535-548
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• 2022

Recently, the construction industry has focused on eco-friendly materials instead of traditional materials due to their harmful effects on the environment. To this end, biopolymers are among proper choices to improve the geotechnical behavior of problematic soils. In the current study, serish biopolymer is introduced as a new binder for the purpose of sand improvement. Serish is a natural polysaccharide extracted from the roots of Eremurus plant, which mainly contains inulins. The effect of serish biopolymer on sand treatment has been investigated through performing unconfined compressive strength (UCS), California bearing ratio (CBR), as well as wind erosion tests. The results demonstrated that serish increased the compressive strength of dune sand in both terms of UCS and CBR. Also, wind erosion resistance of the sand was considerably improved as a result of treatment with serish biopolymer. A microstructural study was also conducted via SEM images; it can be seen that serish coated the sand particles and formed a strong network.

• KSBB Journal
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• 제13권5호
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• pp.554-560
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• 1998

Biopolymer from alkaline-tolerant Bacillus so. was purified, and its physico-chemical and structural properties were investigated. Crude biopolymer, precipitated by acetone from culture broth was fractionated into two fractions by gel chromatography on Sephadex G-200. Among two fractions, one fraction(PS I), which an acidic biopolymer precipitated by the CPC(cetylpyridinium chloride) treatment was studied further. PS I fraction had carboxyl groups and was positive at color reaction of sugar. PS I fraction also showed UV absorbance at 190-225nm. The purified acidic biopolymer was composed of 4% glucose, 8% glucosamine and 88% glutamic acid. Sugar components of the purified acidic biopolymer seemed to be linked to PGA(polyglutamic acid) which existed in the from of ${\gamma}$-peptide bond. By the results of Smith degradation of sugar components, glucose and glucosamine was bound by 1,3 glocosidic linkage. Therefore, this biopolymer was a glycopeptide, oligosaccaride ${\gamma}$-PGA. We concluded that the equivalent weight and the molecular weight of this biopolymer were estimated as about 171 and 5x105 dalton, respectively.

• 한국식품과학회지
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• 제29권1호
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• pp.138-144
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• 1997

토양으로부터 분리한 Metarrhizium anisopliae (Metschn.) Sorok이 생산하는 biopolymer YU-122의 물리, 화학적 특성을 알아보고, 그의 식품 및 생물산업에의 응용 가능성을 검토하여보았다. Biopolymer YU-l22의 flow behavior index (n)는 0.173으로서 pseudoplastic한 non-Newtonian용액 특성을 보였으며, 농도, 온도 및 pH의 변화에 따른 점도의 변화를 검토한 결과 0.3% 이상의 농도에서부터 농도의 증가에 따라 급격한 점도의 증가를 나타냈으며, $60^{\circ}C$, pH 11.0까지 점도의 변화 없이 안정한 성질을 갖는 것으로 나타났다. 또한 기존에 보고된 다른 polymer와는 달리 $NaCl,\;CaCl_2$ 등의 무기염의 첨가에 대하여서도 점도의 변화를 나타내지 않았다. Metarrhizium anisopliae (Metschn.) Sorok이 생산하는 biopolymer YU-122의 산업적 응용성을 검토하기 위하여 유화안정제로서의 성질 및 film 형성능, 해빙시간에 미치는 영향 등을 검토한 결과 옥수수유를 사용한 경우 xanthan gum보다 4배인 120시간동안 유화효과를 나타내었다. 또한 xanthan gum보다 우수한 film 향성능을 나타내었으며, 1% biopolymer YU-122용액에서 해빙시간이 3배까지 연장되어 해빙에 미치는 영향도 매우 우수한 것으로 나타났다.

• Geomechanics and Engineering
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• 제25권1호
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• pp.31-40
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• 2021

Injection grouting is one of the most common ground improvement practice to increase the strength and reduce the hydraulic conductivity of soils. Owing to the environmental concerns of conventional grout materials, such as cement-based or silicate-based materials, bio-inspired biogeotechnical approaches are considered to be new sustainable and environmentally friendly ground improvement methods. Biopolymers, which are excretory products from living organisms, have been shown to significantly reduce the hydraulic conductivity via pore-clogging and increase the strength of soils. To study the practical application of biopolymers for seepage and ground water control, in this study, we explored the injection capabilities of biopolymer-based grout materials in both linear aperture and particulate media (i.e., sand and glassbeads) considering different injection pressures, biopolymer concentrations, and flow channel geometries. The hydraulic conductivity control of a biopolymer-based grout material was evaluated after injection into sandy soil under confined boundary conditions. The results showed that the performance of xanthan gum injection was mainly affected by the injection pressure and pore geometry (e.g., porosity) inside the soil. Additionally, with an increase in the xanthan gum concentration, the injection efficiency diminished while the hydraulic conductivity reduction efficiency enhanced significantly. The results of this study provide the potential capabilities of injection grouting to be performed with biopolymer-based materials for field application.

• Journal of Microbiology and Biotechnology
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• 제14권4호
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• pp.658-664
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• 2004

To find a new utilization of rice bran, nine higher fungi were examined for the production of exo-biopolymer with macrophage stimulating activity from rice bran. Among the exo-biopolymers produced from submerged cultures, Lentinus edodes showed the highest activity, followed by Grifola frondosa, Schizophyllum commune, and Coriolus versicolor. L. edodes also had the most potent macrophage stimulating activity in a liquid culture rather than in a solid culture. In order to improve rice bran utilization and the yield of exo-biopolymer with macrophage stimulating activity, the treatment of Rapidase effectively increased the macrophage stimulating activity (about 30% increase), whereas the other enzymes (Econase, Viscozyme, Ultraflo, Celluclast, and Thermylase) treatments did not increase the macrophage stimulating activity. Exo-biopolymer with macrophage stimulating activity from L. edodes contained mainly neutral sugars (58.7%) with considerable amounts of uronic acid (32.2%) and a small amount of proteins (9.1%). Component sugars of exo-biopolymer consisted of mainly arabinose, galactose, glucose, mannose, and xylose (0.95:0.81:0.96:1.00:0.39, respectively). When the exo-biopolymer was treated with $NaIO_4, NaClO_2$, and pronase, the $NaClO_2$ treatment and pronase digestion had little effect, whereas $NaIO_4$ oxidation significantly decreased the macrophage stimulating activity (47.6% reduction at $100\mug/ml$). Therefore, the carbohydrate moiety in exo-biopolymer from L. edodes plays an important role in the expression of the macrophage stimulating activity.