Chitin

About: Chitin is a research topic. Over the lifetime, 6590 publications have been published within this topic receiving 253993 citations.

Chitinase-overproducing mutant of Serratia marcescens.

Abstract: Genetic modification of Serratia marcescens QMB1466 was undertaken to isolated mutants which produce increased levels of chitinolytic activity. After mutagenesis with ultraviolet light, ethyl methane sulfonate or N-methyl-N'-nitro-N-nitrosoguanidine, 19,940 colonies were screened for production of enlarged zones of clearing (indicative of chitinase activity) on chitin-containing agar plates. Forty-four chitinase high producers were tested further in shake flask cultures. Mutant IMR-1E1 was isolated which, depending on medium composition, produced two to three times more than the wild type of the other components of the chitinolytic enzyme system--a factor involved in the hydrolysis of crystalline chitin and chitobiase. After induction by chitin, endochitinase and chitobiase activity appeared at similar times for both IMR-1E1 and QMB1466, suggesting possible coordinate control of these enzymes. The results are consistent with IMR-1E1 containing a regulatory mutation which increased production of the components of the chitinolytic enzyme system and/or with IMR-1E1 containing a tandem duplication of the chitinase genes. The high rate of reversion of IMR-1E1 to decreased levels of chitinase production suggests that the overproduction of chitinase by IMR-1E1 is due to a tandem gene duplication.

Reactivity characteristics of squid β-chitin as compared with those of shrimp chitin: High potentials of squid chitin as a starting material for facile chemical modifications

Abstract: Chemical reactivity of β-chitin isolated from squid pens has been examined in various reactions to elucidate the possibility of facile modifications in simple manners leading to the preparation of derivatives with well-defined structures. β-Chitin swelled in common solvents such as methanol and pyridine unlike the ordinary α-chitin and exhibited much higher reactivity than β-chitin. Free amino groups present in β-chitin were easily and selectively acetylated with acetic anhydride in methanol to give chitin with a uniform structure, poly(N-acetyl-D-glucosamine). When acetylation reaction was carried out in pyridine, O-acetylation proceeded smoothly besides N-acetylation. In the presence of 4-dimethylaminopyridine as the catalyst, even full acetylation was achieved under mild conditions. Tosylation was also quite efficient in pyridine without side reactions such as N-deacetylation which is unavoidable in the tosylation of α-chitin. β-Chitin also enabled direct tritylation in pyridine in the presence of 4-dimethylaminopyridine. All these reactions were quite sluggish with β-chitin, and no reactions or only very low extents of substitution were observed, indicating the high potential of β-chitin as a versatile starting material for facile modification reactions. © 1994 John Wiley & Sons, Inc.

Effect of Treatment Methods on Chitin Structure and Its Transformation into Nitrogen-Containing Chemicals

Abstract: Chitin treatment using different methods, including ball mill grinding, steam explosion, alkaline treatment, phosphoric acid, and ionic liquid (IL) dissolution/reprecipitation have been systematically investigated. The chitin structures were thoroughly investigated by using a series of analytical techniques, and the reactivity after each treatment was evaluated in dehydration and liquefaction reactions. The parallel studies enable direct comparisons of these methods and help to establish the structure-activity correlations. Ball mill grinding in dry mode was the most effective method, with the crystal size and the hydrogen-bond network being the two crucial factors in enhancing the reactivity. Remarkably, the yield of 3-acetamido-5-acetylfuran (3A5AF) from chitin dehydration increased to the highest amount (28.5 %) after ball mill grinding (the previous record yield was 7.5% for untreated chitin).

Conversion of chitin and N-acetyl-D-glucosamine into a N-containing furan derivative in ionic liquids

Abstract: Direct conversion of chitin to 3-acetamido-5-acetylfuran (3A5AF) in a range of ionic liquids (ILs) has been systematically investigated. 10 ILs with different cations and anions were tested as the solvent and 25 additives were screened. The results revealed that the presence of Cl in the IL is essential. In addition to the solubility enhancement of chitin in Cl containing ILs, the Cl anion appeared to participate in the chitin reaction cycle in IL solvents. 3A5AF can be obtained in some ILs, such as [BMIm]Cl, without any additive. Significantly enhanced yields of 3A5AF were obtained in [BMIm]Cl using boric acid and hydrochloric acid (HCl) as additives at 180 °C, a lower temperature than using organic solvents (215 °C). Kinetic studies showed that the product formed very quickly within 10 min, with much higher initial rate than using organic solvents. Recovered chitin was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and elemental analysis (EA). In an effort to improve the yield, extraction and distillation were attempted for both chitin and chitin monomer, N-acetyl-D-glucosamine (NAG). Further studies were performed on NAG to see if acidic ILs would lead to enhanced reactivity. However, these were less effective.