• Journal of Microbiology and Biotechnology
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• v.24 no.9
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• pp.1178-1188
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• 2014

In this study, the yeast Pichia pastoris was genetically modified to assemble minicellulosomes on its cell surface by the heterologous expression of a truncated scaffoldin CipA from Clostridium acetobutylicum. Fluorescence microscopy and western blot analysis confirmed that CipA was targeted to the yeast cell surface and that NtEGD, the Nasutitermes takasagoensis endoglucanase that was fused with dockerin, interacted with CipA on the yeast cell surface, suggesting that the cohesin and dockerin domains and cellulose-binding module of C. acetobutylicum were functional in the yeasts. The enzymatic activities of the cellulases in the minicellulosomes that were displayed on the yeast cell surfaces increased dramatically following interaction with the cohesin-dockerin domains. Additionally, the hydrolysis efficiencies of NtEGD for carboxymethyl cellulose, microcrystal cellulose, and filter paper increased up to 1.4-fold, 2.0-fold, and 3.2-fold, respectively. To the best of our knowledge, this is the first report describing the expression of C. acetobutylicum minicellulosomes in yeast and the incorporation of animal cellulases into cellulosomes. This strategy of heterologous cellulase incorporation lends novel insight into the process of cellulosome assembly. Potentially, the surface display of cellulosomes, such as that reported in this study, may be utilized in the engineering of S. cerevisiae for ethanol production from cellulose and additional future applications.

• Journal of Biosystems Engineering
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• v.43 no.1
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• pp.59-71
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• 2018

Purpose: Cellulose nanocrystals (CNCs) are natural polymers that have been promoted as a next generation of new, sustainable materials. CNCs are invaluable as reinforcing materials for composites because they can impart improved mechanical, chemical, and thermal properties and they are biodegradable. The purpose of this review is to provide researchers with information that can assist in the application of CNCs extracted from waste agricultural byproducts (e.g. rice husks, corncobs, pineapple leaves). Methods & Results: This paper presents the unique characteristics of CNCs based on agricultural byproducts, and lists processing methods for manufacturing CNCs from agricultural byproducts. Various mechanical treatments (microfluidization and homogenization) and chemical treatments (alkali treatment, bleaching and hydrolysis) can be performed in order to generate nanocellulose. CNC-based composite properties and various applications are also discussed. Conclusions: CNC-based composites from agricultural byproducts can be combined to meet end-use applications such as sensors, batteries, films, food packaging, and 3D printing by utilizing their properties. The review discusses applications in food engineering, biological engineering, and cellulose-based hydrogels.

• Journal of the Korean Wood Science and Technology
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• v.42 no.2
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• pp.119-129
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• 2014

This work undertook to prepare nanofibers of cellulose nanofibrils (CNF)/polyvinyl alcohol (PVA) composite by electrospinning, and characterize the electrospun composite nanofibers. Different contents of CNFs isolated from hardwood bleached kraft pulp (HW-BKP) by 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation were suspended in aqueous polyvinyl alcohol (PVA) solution, and then electrospun into CNF/PVA composite nanofibers. The morphology and dimension of CNFs were characterized by transmission electron microscopy (TEM), which revealed that CNFs were fibrillated form with the diameter of about $7.07{\pm}0.99$ nm. Morphology of the electrospun nanofiber observed by field-emission scanning electron microscopy (FE-SEM) showed that uniform CNF/PVA composite nanofibers were manufactured at 1~3% CNF contents while many beads were observed at 5% CNF level. Both the viscosity of CNF/PVA solution and diameter of the electrospun nanofiber decreased with an increase in CNF content. The diameter and its distribution of the electrospun nanofibers helped explain the differences observed in their morphology. These results show that the electrospinning method was successful in preparing uniform CNF/PVA nanofibers, indicating a great potential for manufacturing consistent and reliable cellulose-based nanofibrils for scaffolds in future applications.

• Journal of Microbiology and Biotechnology
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• v.7 no.5
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• pp.305-309
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• 1997

Bacillus stearothermophilus No. 236, an effective xylanolytic bacterium, produced an extracellular carboxymethyl cellulase when the strain was grown on xylan. The carboxymethyl cellulase was purified to homogeneity as judged by SDS-PAGE and zymogram, The carboxymethyl cellulase had a pI of 4.0, and a molecular mass of 95 kDa. The highest level of enzyme activity was observed at pH 6.5 and $60^{\circ}C$. The $K_m$, and $V_{max}$ values of the enzyme to carboxymethyl cellulose were 20.8 mg/ml and $0.63 {\mu}mole$/min/mg protein, respectively, The enzyme was found to act also on filter paper and xylan as well as carboxymethyl cellulose. Therefore, it is expected that this xylanolytic strain isolated from soil could be efficiently used for xylan biodegradation.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.6
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• pp.1211-1219
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• 2001

The electro-rheological(ER) fluids for smart hydraulic system are a class of colloidal dispersion which exhibit large reversible Changes in their rheological behavior when they are subjected to external electrical fields. This paper presents experimental results on material properties of an ER fluids subjected to electrical fatigues. As a first step, ER fluid is made of methyl cellulose(MC) choosing 25% of particle weight-concentration. Following the construction of test mechanism for durability estimation, the dynamic yield shear stress and the current density for the ER fluids of MC component are experimentally distilled as a function of electric field. In addition, the surface roughness of the employed electrode are evaluated as a function of the number of the electric-field cycles.

• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2207-2210
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• 2010

This paper describes the preparation and study of thermally stimulated discharge conductivity (TSDC) study of cellulose triacetate (CTA) - multiwalled carbon nanotubes (MWNTs) film thermoelectrets. TSDC has been carried out in the temperature range 308 - 503 K and at four different polarizing fields. The conductivity of the polymer blends increased with increase in temperature showing a semi-conducting behavior. The apparent activation energy also showed a pronounced effect with the increase in the content of MWNTs.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.7
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• pp.1075-1081
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• 2008

Eco-friendly processing using enzymes has been focused in textile industry in order to reduce environmental pollutions. This paper was suggested to hydrolyze non-cellulose, such as fats and waxes in cotton fabrics by lipase treatment. Enzymatic treatment conditions were controlled according to pH, temperature, enzyme concentration, and treatment time. The physical properties of the lipase-treated cotton fabrics were evaluated by measuring weight loss, moisture regain and dyeing properties. The surface morphology of lipase-treated cotton fabrics were observed by SEM. As a result, the optimum conditions for the lipase treatment were at pH 4.2, temperature 50$^{\circ}C$, concentration 50%, and treatment time 90 minutes. Calcium chloride and Triton X-100 were effective auxiliaries in lipase treatment.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.11a
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• pp.64-67
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• 2000

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.45 no.1
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• pp.35-41
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• 2013

In this study, we investigated the effect of the number of passes through agrinder on the pore characteristics of nanofibrillated cellulose (NFC) mat. The beaten pulp suspension was used to make NFC suspension using a grinder. To evaluate the pore characteristics of a NFC mat, the surface morphology of the dried NFC mat was observed with FE-SEM and the specific surface area was analyzed with BET nitrogen gas adsorption. The structure of NFC mat was changed with the different number of passes and drying methods. The specific surface area of NFC mat increased with the increase in the number of passes. The 20-passed NFC mat had 20 times larger specific surface area ($141m^2/g$) compared to the 0-passed NFC mat. The specific surface area was strongly correlated with the average pore size in NFC mat. The average pore diameter in NFC mat was calculated from the gas sorption isotherms using BJH model. The value was 13 - 15 nm, indicating that the NFC mat had mesoporous structure.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.4
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• pp.42-48
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• 1998

The bacterial cellulose(BC) has many unique properties that are potentially and commercially beneficial. In order to enhance inherently inferior physical property of chemithermomechanical pulp(CTMP) sheet, chemical pulp has been used widely. Bacterial cellulose also has an enhanced sheet strength because of its unique physical and morphological features. This study was carried out to inverstigate the effect of BC addition on physical properties of CTMP sheets. The effect of BC addition on its optical properties was also discussed. The apparent density, internal bond strength, Young's modulus, tensile strength and folding endurance of CTMP sheet are increasing with increase of BC contents. This strength increase would be attributed to the increase of relative bonding sites among pulp fibers by addition of BC which has microfibrillar structure with very high specific surface areas. There were not so significant changes in opacity of CTMP sheet upto 20% addition level of BC, while over 40% addition, the opacity gradually decreased and levelled off. Porosity is decreased with addition of BC. This decrease would be attributed to densification of sheet by fine and filamentous structure of BC fibers.