Chitin, chitosan recovered from fly crabs shells have been investigated by the elemental analysis, potentiometric titraton and FT–IR spectrometry methods. The molecular weght of chitosan was determined by measuring their viscosity. The adsorption kinetics of reactive dye and equilibrium conditions has been investigated. The adsorption of reactive dye on chitin and chitosan proceeds according to pseudo – second – order kinetic equation. Adsorption investigations under equilibrium conditions showed that. Theses results were fitted by both Langmuir and Freudlich models.

The effects of the insecticide diflubenzuron (DFB) on the growth characteristics of two gram negative soil bacterial isolates were examined. The bacterial isolates were grown in the presences of varying amounts of DFB and showed no apparent change in cell numbers, over time, when compared to control cultures. However, one of the two isolates tested showed a delayed response in chitinase production, over the same time period, as determined by radioisotopic methodology. Chitinase fractions obtained from cell free culture supernatants, concentrated by ultrafiltration and purified by affinity chromatography, were examined for activity in the presence of DFB. High performance liquid chromatography (HPLC) techniques were utilized in the identification and quantification of products from control and experimental samples. Due to the loss of overall chitinase activity in the supernatants, this technique proved ineffective in determining chitinase response to DFB. / Department of Biology

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 7 uppsatser.

Thesis (Master)--İzmir Institute of Technology, İzmir, 2004 / Includes bibliographical references (leaves. 94).

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

A finalidade deste trabalho foi obter suspensões aquosas estáveis de beta-quitina (GA = 79%) explorando o uso de ultrassom de alta intensidade, e preparar filmes autossuportados por casting a partir de suspensões de beta-quitina, soluções aquosas de quitosana (GA = 4,9%) e da combinação de ambas em diferentes proporções. Assim, foram preparados os filmes BQF (100% beta-quitina) e QF (100% quitosana), e os filmes compostos BQ80/Q20, BQ50/Q50, BQ20/Q80, sendo que as porcentagens de beta-quitina e quitosana são indicadas pelos sub-índices empregados na identificação dos referidos filmes. Foi constatado por análises de espectroscopia na região do infravermelho e espectroscopia de ressonância magnética nuclear de hidrogênio que o tratamento de ultrassom não alterou a estrutura de beta-quitina, enquanto a viscosimetria capilar em solução diluída mostrou ligeiro decréscimo (16%) da viscosidade intrínseca, indicando a ocorrência de despolimerização em baixa extensão. As análises de microscopia eletrônica de varredura e microscopia de força atômica mostraram que os filmes com maiores teores de beta-quitina exibiram superfícies mais heterogêneas, granulares e rugosas, enquanto a presença de quitosana resultou em filmes mais homogêneos e significativamente menos rugosos. Assim, os filmes BQF e QF apresentaram valores de rugosidade média quadrática (RMS) 225,0 nm e 21,6 nm , respectivamente. As medidas de ângulo de contato revelaram que o filme QF é o mais hidrofílico (θ ≈ 75,40), enquanto os filmes compostos BQ20/Q80, BQ50/Q50 e BQ80/Q20, que têm teores crescentes de beta-quitina, foram mais hidrofóbicos, apresentando ângulos de contato 87,50, 95,60 e 95,20, respectivamente. As análises termogravimétricas revelaram que o tratamento de ultrassom favorece o intumescimento das partículas de beta-quitina e que o baixo grau de ordem dos filmes contribui para diminuir a estabilidade térmica quando comparada à beta-quitina na forma de pó. As análises de calorimetria exploratória diferencial dos filmes compostos mostraram que a eliminação de água demanda maior energia quanto maior o teor de beta- quitina, evidenciando a ocorrência de fortes interações entre as cadeias de beta-quitina e moléculas de água. Assim, os resultados mostraram que o tratamento de ultrassom permitiu o processamento de beta-quitina/quitosana para a formação de filmes autossustentados sem a utilização de solventes orgânicos, e que os filmes exibem características e propriedades que dependem fortemente de sua composição, i. e. dos teores de beta-quitina e quitosana. / The purpose of this study was to obtain stable aqueous suspensions of beta-chitin (GA = 79%) exploring the use of high intensity ultrasound, and to prepare self-sustained films by casting from suspensions of beta-chitin, chitosan aqueous solutions (GA = 4.9%) and from the combination of both, in different proportions. Thus, the films BQF (100% of beta-chitin) and QF (100% of chitosan) and compound films BQ80/Q20, BQ50/Q50, BQ20/Q80 were prepared, the percentages of beta-chitin and chitosan being indicated by the sub-indices used in the identification of those films. It has been found by infrared spectroscopy and proton nuclear magnetic resonance spectroscopy that the ultrasound treatment did not alter the structure of beta-chitin, while the capillary viscometry in dilute solution showed a slight decrease (16%) of intrinsic viscosity indicating the occurrence of depolymerization at low extension. Atomic force microscopy and scanning electron microscopy showed that the films with higher content of beta-chitin exhibited more heterogeneous, granular and rough surfaces, while the presence of chitosan resulted in significantly more homogeneous and less rough films. Thus, QF and BQF films showed values of mean square roughness (RMS) 225.0 nm and 21.6 nm, respectively. The contact angle measurements showed that QF (θ ≈ 75.40) is the more hydrophilic film, while the composite films BQ20/Q80, and BQ50/Q50, BQ80/Q20, which have increasing contents of beta-chitin were more hydrophobic, exhibiting contact angles 87.50, 95.60 and 95.20, respectively. Thermogravimetric analysis showed that the ultrasound treatment favored the swelling of the particles of chitin and that the low degree of order of the films contributed to decrease the thermal stability when compared to beta-chitin in powder form. The differential scanning calorimetry of the compound films showed that the elimination of water requires more energy the higher the content of beta-chitin, indicating the occurrence of strong interactions between the chains of beta- chitin and water molecules. Thus, the results showed that the ultrasoud treatment allowed the processing beta- chitin/chitosan for the formation of self-sustained films without the use of organic solvents, and that the films exhibited characteristics and properties strongly dependent on their composition, i. e. the content of beta-chitin and chitosan.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20712号 / 工博第4409号 / 新制||工||1685(附属図書館) / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 跡見 晴幸, 教授 森 泰生, 教授 浜地 格 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Cellulose nanofibers (CNFs) have established widespread attention in various industries with their potential applications. Production of CNFs from agricultural post harvesting wastes has several cost-effective and eco-friendly benefits. The objective of this research was to prepare four different types of CNFs from cotton stalks by different chemical treatments followed by ultra-sonication. CNFs via untreated bleached pulp, sulfuric acid hydrolysis, and TEMPO [(2,2,6,6-tetramethylpiperidin-1-yl) oxy radical]-mediated oxidation process were produced. Physical and chemical properties of these CNFs were investigated by morphological (FE-SEM, AFM), structural (FTIR), and thermal gravimetric analysis (TGA). Developed TEMPO-oxidized cellulose nanofibers (TEMPO-CNFs) were brighter and higher in yields (>90%). It was the first time uniform and very small sized (3-15 nm diameter and 10-100 nm length) nanofibers were produced. In application purpose, TEMPO-CNFs were introduced into chitosan matrix (prepared from shrimp exoskeletons) for the development of bionanocomposite food packaging films and into chitin for hydrogels preparation in order to eliminate heavy metals from water bodies. Development of bionanocomposite films (chitosan/TEMPO-CNFs compositions) was an effective and complete green approach with enhanced mechanical and barrier properties. Also use of TEMPO-CNFs in this method makes it possible to produce flexible, transparent, and low cost food packaging films with good antimicrobial activity against Salmonella enterica, E. coli O157:H7, and Listeria monocytogenes. In a similar way, generation of recyclable biobased adsorbents (chitin/TEMPO-CNFs compositions) with superior adsorption capacity and high surface area were effectively used in lead (Pb2+) removal from aqueous solutions, thus provide new opportunities as economical and environmentally friendly green remediation.

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Previous studies have indicated that fermentation with yeast strains whose cell walls contain higher chitin levels may lead to reduced wine haze formation. In order to adjust cell wall chitin levels, more information on the regulation of chitin synthesis in wine-relevant yeast is required. Yeast cells are known to increase chitin levels when subjected to certain environmental changes such as an increase in temperature. The main aim of this project was to investigate chitin accumulation and synthesis in wine yeast strains when exposed to environmental change. This was achieved by subjecting the strains to various environmental conditions and comparing chitin levels. The information gained may aid future selection and/or manipulation of yeast strains for the production of higher chitin levels. Three Saccharomyces cerevisiae strains and two Saccharomyces paradoxus strains were subjected to conditions that had been linked to a change in chitin synthesis in past studies in laboratory yeast strains. Of the conditions used in this study, the addition of calcium to a rich media led to the highest cell wall chitin levels. The data also show that chitin synthesis is largely strain dependant. Two conditions which resulted in increased chitin deposition were chosen for gene expression analyses, using strains with strongly diverging average chitin levels. Results showed that an increase in chitin levels correlates with an increase in expression of GFA1, the gene encoding for the first enzyme of the chitin synthesis pathway. Overall, this study provides novel insights into chitin synthesis in Saccharomyces cerevisiae wine yeast strains as well as Saccharomyces paradoxus strains, with possible future implications on haze prevention studies. / AFRIKAANSE OPSOMMING: Vorige studies het aangetoon dat fermentasie met gisrasse waarvan die selwande hoë chitienvlakke bevat, kan lei tot verminderde wynwaasvorming. Om selwandchitienvlakke aan te pas, word daar meer inligting rakende die regulering van chitienvlakke in wyn gisrasse verlang. Dit is bekend dat gisselle chitienvlakke verhoog wanneer die selle onderwerp word aan sekere veranderinge in die omgewing soos ’n verhoging in temperatuur. Die hoofdoel van hierdie projek was om die chitienopbou en -sintese in wyngisrasse te ondersoek waar gis blootgestel word aan omgewingsveranderinge. Dit is bereik deur die selle aan verskeie omgewingstoestande bloot te stel en chitienvlakke met mekaar te vergelyk. Die inligting hieruit verkry kan toekomstige gisraskeuses asook die manipulering van gisrasse met die oog op hoër vlakke van chitienproduksie vergemaklik. Drie Saccharomyces cerevisiae rasse en twee Saccharomyces paradoxus rasse is onderwerp aan toestande wat in vorige studies gekoppel is aan ’n verandering in chitienvorming in laboratorium-gisrasse. Van die toestande toegepas in hierdie studie, het die toevoeging van kalsium tot ’n nutrientryke medium gelei tot die hoogste chitienvlakke in selwande. Die data toon ook aan dat chitiensintese hoofsaaklik rasverwant is. Twee toestande wat gelei het tot verhoogde chitienafsetting is gekies vir geen-uitdrukkingsanalise, terwyl rasse gebruik is met gemiddelde chitienvlakke wat wyd uiteenlopend is. Die resultate het getoon dat ’n verhoging in chitienvlakke ooreenstem met ’n verhoging in die uitdrukkingsvlakke van GFA1, die geen wat kodeer vir die eerste ensiem in die chitiensintesebaan. Oor die algemeen verskaf hierdie studie nuwe insigte oor chitiensintese in Saccharomyces cerevisiae wyngisrasse en Saccharomyces paradoxus rasse en verskaf dit belangrike inligting vir moontlike toekomstige studies oor waasvoorkoming.

Submitted in complete fulfillment for the Degree of Master of Technology (Biotechnology), Durban University of Technology, Durban, South Africa, 2014. / Chitin, a highly insoluble 1,4- -linked polymer of N-acetyl- -D-glucosamine, is the second-most abundant bio-polysaccharide in nature after cellulose. Most chitinolytic fungi are known to produce more than one kind of chitinase. The recent sequencing of the Thermomyces lanuginosus SSBP genome by our group has revealed four putative family 18 chitinases. In this study, three novel chitinase genes (chitl, chit2 and chit3) and the previously reported chit4 gene were cloned from Thermomyces lanuginosus SSBP and their gene structures were analysed. chit3, encoding a 36.6 kDa protein, and chit4, encoding a 44.1 kDa protein, were successfully expressed in Pichia pastoris. The recombinant Chit3 and Chit4 enzymes exhibited optimum activity at pH 4.0 and 5.0 and at 40oC and 50°C, respectively. Chit3 was stable at 40oC and retained 71% of its activity at 50°C after 60 min, while Chit4 was stable at 50°C and retained 56% of its activity at 60°C after 30 min. Both enzymes produced chitobiose as the major product using colloidal chitin, chitooligosaccharides and shrimp shell powder as substrates. Of the fungal strains tested, Chit3 displayed antifungal activity against Penicillium sp. and Aspergillus sp. This is the first report on the multi-chitinolytic system of T. lanuginosus and enzyme characterization has shown the potential of the enzymes to be used in degradation of the under-utilized bio-resource chitin. / PDF Full-text unavailable. Please refer to hard copy for Full-text / M