Acid modification of lignocellulosic derived material for dye and heavy metals removal: A review

M.S. Akindolie,H.J. Choi 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.2

Researchers have tested Lignocellulose derived material (LDMs) from different sources ranging from agricultural to wood in order to facilitate the adsorption of chemical contaminants, such as heavy metals and dyes from water bodies, to eradicate water contamination. However, different methods have been employed to modify the nature of the LDMs to enable their suitability for contaminants removal. Among all these methods, acid modification of LDMs has gained a lot of attention. This review focused on the use of acid modification LDMs for the removal of anionic and cationic dyes, and heavy metals in water. The characteracerization techniques employed in studying the morphology and functional groups of the LDMs were discussed. The adsorption dynamics and mechanisms of reported studies were extensively summarized. The reported adsorption capacity of unmodified LDMs in the available liturature is in the range of 4.44–156.00 ㎎/g while for the modified is between 80.05–250.01 ㎎/g for dye removal. The adsorption capacity of modified LDMs reported was 1.60–18.03 times higher than the unmodified because of additional functional groups such as -SO₃ from sulphuric acid modification. Finally, the future outlook and challenges of this method were pulled together.

화학적 수식에 의한 Bacillus stearothermophilus β-D-Xylosidase의 연구

서정한,최용진 한국산업미생물학회 1994 한국미생물·생명공학회지 Vol.22 No.6

E. coli JM109/pMG1 재조합 균주가 생산하는 Bacillus stearothermophilus β-Dxylosidase의 효소활성과 관련된 필수 아미노산 잔기를 화학적 수식(chemical modification) 법을 이용, 분석하여 다음과 같은 결과를 얻었다. B. stearothermophilus β-D-xylosidase의 구성 아미노산 잔기 중에서 histidine, tyrosine, serine, methionine 및 tryptophan 등은 효소 활성에 직접적인 관계를 가지고 있지 않는 것으로 판명되었으며 carboxylic amino acid와 cysteine은 효소 작용에 직접 관련된 중요한 역할을 하고 있는 아미노산 잔기로 밝혀졌다. 한편 xylobiose 기질에 의한 효소 활성 보호 실험결과에 의하면 상기 두 종의 효소 활성 필수 아미노산 잔기는 효소-기질 결합 단계에서 중요한 역할을 하는 것으로 추측되었다. 또한 각각 carboxylic amino acid와 cysteine modifier인 Woodward's Reagent K(WRK)와 N-ethylmaleimide의 효소 불활성화 반응의 kinetics를 분석해 본 결과 WRK의 경우에는 두개의 carboxylic amino acid를, N-ethylmaleimide의 경우는 한개의 cysteine 잔기를 수식함으로써 거의 완전한 효소 불활성화 현상을 초래하는 것으로 계산되었다. Essential amino acids involving in the catalytic mechanism of the β-D-xylosidase of Bacillus stearothermophilus were determined by chemical modification studies. Among various chemical modifiers tested N-bromosuccinimide (NBS), p-hydroxymercurybenzoate (PHMB), N-ethylmaleimide, 1-[3-di-ethylamino)-propy1]-3-ethylcarbodi-imide(EDC), and Woodward's Reagent K(WRK) inactivated the enzyme, resulting in the residual activity of less than 20%. WRK reduced the enzyme activity by modifying carboxylic amino acids, and the inactivation reacion proceeded in the form of pseudo-first-order kinetics. The double-lagarithmic plot of the observed pseudo-first-order rate constant against the modifier concentration yielded a reaction order of 2, indicating that two carboxylic amino acids were essential for the enzyme activity. The β-D-xylosidase was also inactivated by N-ethylmaleimide which specifically modified a cysteine residue with a reaction order of 1, implying that one cysteine residue was important for the enzyme activity. Xylobiose protected the enzyme against inactivation by WRK and N-ethylmaleimide, revealing that carboxylic amino acids and a cysteine residue were present at the substrate-binding site of the enzyme molecule.

Challenging the Hypothesis of de novo Biosynthesis of Bile Acids by Marine Bacteria

Tueros Felipe Gonzalo,Ellabaan Mostafa M. Hashim,Henricsson Marcus,Vazquez-Uribe Ruben,Bäckhed Fredrik,Sommer Morten Otto Alexander 한국미생물·생명공학회 2022 한국미생물·생명공학회지 Vol.50 No.1

Bile acids are essential molecules produced by vertebrates that are involved in several physiological roles, including the uptake of nutrients. Bacterial isolates capable of producing bile acids de novo have been identified and characterized. Such isolates may provide access to novel biochemical pathways suitable for the design of microbial cell factories. Here, we further characterized the ability of Maribacter dokdonensis, Dokdonia donghaensis, and Myroides pelagicus to produce bile acids. Contrary to previous reports, we did not observe de novo production of bile acids by these isolates. Instead, we found that these isolates deconjugated the amino acid moiety of bile acids present in the growth medium used in previous reports. Through genomic analysis, we identified putative bile salt hydrolases, which could be responsible for the different bile acid modifications observed. Our results challenge the hypothesis of de novo microbial bile acid production, while further demonstrating the diverse capacity of bacteria to modify bile acids.

기능성 유지자원으로서의 들깨(Perilla frutescens var. frutescens)의 이용과 가치

최용순 한국자원식물학회 2015 한국자원식물학회지 Vol.28 No.1

The Korean daily intake of vegetable oils has increased about 2.5-fold from 17 g/day to 46 g/day for the lastseveral decades. Perilla (Perilla frutescens var. frutescens) has been cultivated in Korea for a long time as a dietary oil seedwhich has the highest content of α-linolenic acid, accounting for nearly 60%. It is known that the main role of ALA is as aprecursor to the longer-chain ω-3, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), the metabolic productsof α-linolenic acid (ALA, ω-3). Dietary ω-3 fatty acids reduce inflammation and the risk of chronic diseases such as heartdisease, cancer, and arthritis, but they also may act as functional components for cognitive and behavioral function. Thus, α-linolenic acid is one of the essential nutrients in modern dietary patterns in which much linoleic acid is consumed. Nevertheless, perilla oil, rich in α-linolenic acid, can be easily oxidized, giving rise to controversies with respect to shelf life,the deterioration of the product’s commercial value, and further related toxicity. Recent research using genetic modificationshas tried to develop new plant oil seeds that balance the ratio of ω-6/ω-3 fatty acids. Such trials could be a strategy forimproving an easily oxidizable property of perilla oil due to high α-linolenic acid. Alternatively, appropriate application ofantioxidant to the oil can be considerable. 지난 40 여년간 한국인의 식이지방의 섭취는 하루 17 g에서46 g으로 약 2.5배 이상 증가하였다. 들깨는 ALA를 풍부하게 함유한 전통적인 식량자원이다. 대부분의 식물유에 풍부한 LA (ω-6)의 체내 대사물인 AA로부터 생성되는 생리물질은 혈전, 동맥경화, 염증증상 등의 불리한 생리적 작용을 유발한다. 반면에 ALA의 대사산물인 EPA는 AA와 경쟁적으로 작용하여 궁극적으로바람직한 방향으로 생리적 균형을 유지하도록 한다. 그러나 들깨유는 특성상 산화되기 쉬워 저장성과 상품성이 제한적이다. 최근 유전공학을 이용하여 적절한 수준의 ω-6/ω-3 지방산의 비율을 갖는 품종육종이 활발하게 진행되고 있다. 이러한 기술은 기능성과 저장성이 우수한 들깨유를 생산하기 위한 유지자원 개발에 적용할 수 있을 것이다. 덧붙여, 들깨에 항산화물질의 강화는 들깨유의 기능을 강화하는 대안 전략으로 고려될 수 있다.

카르복실산이 그라프트된 PLLA 필름과 이중기공 지지체의 표면 특성 및 세포점착 거동

한동근,안광덕,양희석 한국생체재료학회 2004 생체재료학회지 Vol.8 No.3

Biodegradable poly(L-lactic acid) (PLLA) scaffolds have insufficient initial cell binding sites and limited ability to cell adhesion for in vitro and in vivo tissue culture because of their hydrophobic characteristics. Various efforts are now being attempted to overcome these problems. In this study, the biodegradable nonporous PLLA films and their 3D dual pore scaffolds were fabricated by using the solvent casting method and both gas foaming and phase separation techniques, respectively. The obtained hydrophobic nonporous film and dual pore scaffold surfaces were hydrophilized by using plasma glow discharge treatment and the grafting of carboxyl acid-containing monomers such as acrylic acid (AA), maleic acid (MA), itaconic acid (IA), and trans-aconitic acid (tAA). The surface modification of nonporous films and their dual pore scaffolds was confirmed by water contact angle, electron spectroscopy for chemical analysis (ESCA), and carboxyl group content. The hydrophilized nonporous PLLA films and their dual pore scaffolds which have carboxyl acids on their surface by plasma treatment demonstrated the improved adhesion and proliferation of fibroblasts as compared to the unmodified one.

폴리비닐알코올 스펀지의 표면 개질을 통한 나노영가철의 부착성 향상

김영화,서영교,김효원,황유훈 대한환경공학회 2019 대한환경공학회지 Vol.41 No.9

Objectives : Nanoscale zero-valent iron (nZVI) is known to effectively remove various contaminants due to its small size and high specific surface area, but it is limited in practical water treatment processes due to its difficulty in recovery after use. In this study, a method of immobilizing nZVI on a support material was adopted in order to increase the applicability of nZVI. A polyvinyl alcohol sponge (PVA), which is readily available commercially, was used as a support. For the immobilization of nZVI, it was considered that improving the binding force with the support is essential in order to enhance the pollutant removal efficiency and prevent nZVI loss. A series of surface modification methods with acrylic acid to induce the formation of carboxyl groups were used to improve the bonding strength with the support. Methods : A PVA sponge with a porosity of 90%, an average pore size of 130 μm, and an apparent density of 0.082 g/cm3 was used as a supporting material to immobilize nZVI. The PVA sponge was further cut into cubes of 0.3 × 0.3 × 0.3 cm3 for easy handling. The PVA sponge induced an acrylic acid polymer on the surface through the reaction of acrylic acid and potassium permanganate (PVA-AA). We optimized the conditions in a series of steps to synthesize nZVI on PVA-AA. The conditions considered were the mass ratio of Fe2+ and PVA, Fe2+ adsorption time, and the reduction time using NaBH4. A SEM/EDS analysis was performed to monitor the morphology of the synthesized nZVI on PVA-AA. The reduction reactivity was evaluated through nitrate reduction. Results and Discussion : The amount of Fe2+ adsorption of the support material modified with AA (PVA-AA) was superior to that of the unmodified material (PVA), and the time to reach the adsorption equilibrium was shortened to 30 min. The optimum mass ratio was Fe/PVA-AA = 1. These results indicate that carboxyl groups are formed on the surface of PVA by surface modification using AA and that these carboxyl groups induce strong binding affinity toward iron. The SEM/EDS analysis results showed that AA polymer was formed on the surface of the PVA sponge fiber through AA modification. Moreover, a large amount of nZVI was formed on AA modified PVA (PVA-AA). As the reduction time was increased from 0.5 h to 1 h, the distribution of nZVI iron on the surface and inside the support was more uniform. Finally, the reducing reactivity was evaluated through a nitrate reduction experiment. The reduction efficiency and the reduction rate of PVA-AA-nZVI were 1.9 times and 3.5 times higher than those of PVA-nZVI, respectively. Conclusions : A surface modification technology was developed to enhance nZVI immobilization on a commercially available supporting material. Through the modification of acrylic acid on the surface of a PVA sponge, which can be easily obtained on the market, it was possible to increase the attachment efficiency of nZVI by forming a large number of carboxyl groups on the surface, and subsequently higher pollutant reduction efficiency could be obtained. It is expected that both the economic efficiency and the ability to remove contaminants can be improved by the development of a material having an increased amount of nZVI by the surface modification technology developed in this study. 목적 : 본 연구에서는 나노 영가철의 적용성을 높이기 위하여 지지체 소재에 고정화하는 방법을 택하였으며, 시중에서 쉽게 구할 수 있는 폴리비닐알코올 스펀지(PVA)를 지지체로 사용하였다. 나노 영가철을 고정화시키는 데 있어서 지지체와의 결합력을 향상시키는 것은 오염물질 제거 효율 증대 및 나노 영가철의 탈리를 방지하는 측면에서 중요하다고 판단하였다. 지지체와의 결합력을 향상시키기 위하여 PVA 표면을 아크릴산으로 개질하여 카르복실기를 유도하는 일련의 표면 개질 방법을 사용하였으며, 이를 통하여 나노 영가철 입자의 부착이 향상되는지 여부에 대하여 평가하였다. 방법 : 나노 영가철을 고정하기 위한 담체로써 공극률 90%, 평균 공극 크기 130 μm, 겉보기 밀도 0.082 g/cm3의PVA 스펀지를 사용하였으며, 취급에 용이하도록 0.3 × 0.3 × 0.3 cm3의 정육면체로 가공 후 사용하였다. PVA 스펀지는 아크릴산 및 과망간산칼륨과의 반응을 통하여 표면에 아크릴산 고분자를 유도하였다(PVA-AA). PVA-AA에 나노 영가철을 합성하기 위한 일련의 과정에서의 조건들을 최적화하였다. 고려한 조건은 나노 영가철의 전구 물질인Fe2+와 PVA의 질량 비율, Fe2+ 흡착 시간 및 NaBH4를 이용한 환원 시간이었다. PVA-AA의 Fe2+ 흡착량, 나노 영가철 합성 이후 SEM/EDS 분석을 실시하였으며, 질산성 질소 환원 실험을 통하여 환원 반응성을 평가하였다. 결과 및 토의 : AA로 개질된 지지체 소재(PVA-AA)의 Fe2+ 흡착량이 미개질 소재(PVA)의 경우보다 우수함을 확인할 수 있었고, 흡착 평형에 이르는 시간도 30분으로 단축되는 것을 확인할 수 있었다. 최적 질량 비율은Fe/PVA-AA = 1이었다. 이와 같은 결과는 AA를 이용한 표면 개질을 통하여 PVA 표면의 카르복실기를 형성하였고, 형성된 카르복실기가 철과의 강한 상호 결합을 유도하기 때문인 것으로 파악되었다. SEM/EDS를 통하여 분석한 결과, AA 개질을 통하여 PVA 스펀지 섬유 표면에 AA 고분자가 형성된 것을 확인할 수 있었고, 여기에 나노영가철이 결합된 형태를 확인하였다. AA 개질을 통하여 다량의 나노 영가철이 결합된 것을 확인하였으며, 환원시간을 0.5시간에서 1시간을 늘림에 따라 나노 영가철의 표면과 내부에서의 분포가 더욱 균일해지는 것을 확인할수 있었다. 최종적으로 질산성 질소 환원 실험을 통하여 환원 반응성을 평가하였으며, 표면 개질을 수행하였던PVA-AA-nZVI가 표면 개질을 수행하지 않은 PVA-nZVI에 비하여 환원 효율은 1.9배, 환원 속도는 3.5배 더 높은것으로 나타났다. 결론 : 나노 영가철의 단점을 개선하고 활용성을 높이기 위해 지지체를 활용함에 있어 부착성을 향상시키기 위한표면 개질 기술을 개발하고자 하는 목적으로 수행되었다. 시중에서 쉽게 구할 수 있는 PVA 스펀지 표면을 아크릴산을 개질함을 통하여 표면에 카르복실기를 다수 형성하여 나노 영가철의 부착 효율을 증대시킬 수 있었고, 더 높은 오염물질 환원 효율을 얻을 수 있었다. 영가철이 고정된 소재의 오염물질 환원율을 높이기 위해 중요한 인자는영가철의 함량이라고 할 수 있다. 담체 표면을 개질하고 합성하는 과정으로 영가철의 합성량을 높인 소재의 개발로실제 공정에 적용함에 있어 경제성과 오염물질의 제거 능력 모두 향상시킬 수 있을 것으로 기대된다.

Evaluation of Molecular Weight Distribution, Pasting and Functional Properties, and Enzyme Resistant Starch Content of Acid-modified Corn Starches

Hamit Koksel,Serpil Ozturk,Kevser Kahraman,Arzu Basman,Ozen Ozboy Ozbas,Gi-Hyung Ryu 한국식품과학회 2008 Food Science and Biotechnology Vol.17 No.4

The aim of this study was to produce resistant starch preparations from acid-modified corn starches prepared at various hydrolysis levels (0.5-4.0 hr). Effect of autoclaving cycles on resistant starch (RS) formation was investigated. Molecular weight distribution, pasting and functional properties of acid-modified corn starches were determined. For RS formation native and acid-modified starch samples were gelatinized and autoclaved (1 or 2 cycles). While native and acid-modified starches did not contain any RS, the levels increased to 9.0-13.5% as a result of storage at 95℃ after first autoclaving cycle. Second autoclaving cycle together with storage at 95℃ brought final RS contents of the samples incubated at 4 and 95℃ after the first cycle to comparable level. As acid modification level increased, the amount of high molecular weight fractions decreased, resulting in significant decreases in viscosities (p<0.05). The samples produced in this study had low emulsion stability and capacity values.

The mechanisms of conventional pollutants adsorption by modified granular steel slag

Shaona Wang,Sijian Yao,Kang Du,Rongfang Yuan,Huilun Chen,Fei Wang,Beihai Zhou 대한환경공학회 2021 Environmental Engineering Research Vol.26 No.1

This study was performed to investigate the removal of phosphorus, nitrogen, ammonia and dissolved organic matter (DOM) from domestic wastewater using modified granular steel slag (GSS) as adsorbent. The modification methods include acid modification, alkalinity modification and thermal modification. The GSS modified at 800°C for 1 h was easier to hydrolyze Ca<SUP>2+</SUP>, which could promote the precipitation of phosphates and the ion exchange process of ammonia. Therefore, the adsorptive capacity of GSS for phosphates and ammonia could be significantly improved by the thermal treatment. The acid-modified GSS promoted the adsorption capacity of nitrates by increasing surface protonation, specific surface area and pore size. The highest nitrates adsorption capacity was obtained when GSS was immersed in 1 mol/L HCl solution for 24 h. The presence of nitrates inhibited the adsorption of phosphates by GSS because the adsorption of nitrates and phosphates by GSS depended largely on electrostatic attraction and intermolecular force, and the competition between them reduced the adsorption capacity. Ammonia can promote the hydrolysis of metal ions on the surface of GSS, increase the concentration of metal ions in solution and promote the formation of phosphate precipitation, but ammonia also competed with phosphate for active sites on the surface of GSS. The effect of ammonia nitrogen on phosphate adsorption was the result of the interaction of the two mechanisms. For domestic wastewater, the thermally modified GSS showed the best adsorption rate of total phosphorus and total nitrogen, and the acid-modified GSS had better adsorption capacity for organic matter. The thermally modified GSS had a good application effect in laboratory subsurface flow constructed wetlands.

Acid treatment enhances performance of beads activated carbon for formaldehyde removal

Kang Yu-Jin,Jo Hyung-Kun,Jang Min-Hyeok,Han Gyoung-Jae,Yoon Seong-Jin,Oh Kyeongseok,Park Joo-Il 한국탄소학회 2023 Carbon Letters Vol.33 No.2

This study evaluated how acid treatment affects the ability of customized beads of activated carbon (BAC) to remove formaldehyde from air. Two different acids (hydrofluoric acid and sulfuric acid) were used to modify the surface of BAC prepared from a polymer material. The acid-modified BACs were further subjected to heat treatment. Physical and chemical characteristics of modified and unmodified BACs were investigated using nitrogen adsorption, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray fluorescence, and X-ray photoelectron spectroscopy. Formaldehyde removal was evaluated under both dry and moist conditions. From the results, acid treatment clearly improved the adsorption performance, especially under the moist condition. Qualitative and quantitative surface analyses were conducted, mainly to examine the amount of O-bonds after acid treatment and the formation of S–O or Cl–O on BAC.

Carboxylic acid가 CuInS₂/ZnS 반도체 나노입자의 광학적 특성에 미치는 영향

안시현,최규채,백연경,김영국,김양도,Ahn, Si-Hyun,Choi, Gyu-Che,Beak, Yeun-Kyung,Kim, Young-Kuk,Kim, Yang-Do 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.5

We report the effect of the chain length of carboxylic acid on the photoluminescence(PL) of $CuInS_2$/ZnS nanocrystals. $CuInS_2$/ZnS nanocrystals with emission wavelength ranging from 566 nm through 583 nm were synthesized with zinc acetate and carboxylic acids with various chain length. In this study, $CuInS_2$/ZnS nanocrystals prepared using long chain carboxylic acid showed more improved PL intensity. The origin of strong photoluminescence of the nanocrystals prepared with zinc acetate and long chain carboxylic acid was ascribed to improved size distribution due to strong reactivity between long chain carboxylic acid and zinc acetate.