Papers by Keyword: Deacetylation

Abstract: In this study, Volvariella vovacea (straw mushroom, SM) and Flammulina velutipes (Golden mushroom, GM) were used as a natural source of chitin. The aim of this research is to extract chitin and thus, converted into chitosan via acetylation process. The obtained chitosan was applied in the wastewater treatment process as the coagulant to improve the quality of wastewater. As these two types of mushrooms are readily available in the local area in Northeastern Thailand and relatively cheap. The chitin extraction process was obtained by firstly removing fat, minerals, protein and pigment of SM and GM using petroleum ether, HCl, NaOH and acetone respectively. Extracted chitin was deacetylated by using 50% (v/v) NaOH at 140 ^oC for 2 hours to convert into chitosan. The properties of extracted chitosan was examined by FT-IR and TGA. FTIR spectrum showed the peaks of C-H stretching at 2870 cm^-1 , N-H₂ bending at 1586 cm^-1, N-H stretching at 1026 cm^-1, etc. which corresponded to the standard chitosan. TGA showed the thermal decomposition which is divided into three phases. First stage of weight loss is between 50-115 °C caused by water evaporation. There was no changes of weight during a temperature of 115-268 °C. The second phase during 268-330 °C indicates a significant weight loss which is due tot he saccharide degradation of chitosan and at a temperature more than 330°C refers to the volatile organic material. As a result of TGA, it can be confirmed that the extracted chitosan from SM and GM is very similar to the standard commercial chitosan. After that, 3 g of extracted chitosan was mixed with 300 mL of deionized water and 6 mL of acetic acid was added for 24 hours to prepare the chitosan coagulant. Then, it was dropped in the separate jar which contained high TSS, COD and BOD wastewater. The results showed that chitosan biocoagulant could reduce TSS, COD and BOD by 62, 62 and 88% respectively which proved to be efficient in the use of wastewater treatment.

Abstract: Chitosan is a natural biopolymer derived by deacetylation of chitin from the two main sources of crustaceans, shrimp and crabs. Chitosan, which is soluble in acidic solutions, is used in many applications (biomedical/pharmaceutical, water engineering, food, cosmetics). There have been many researchers who have developed a process of deacetylation of chitin from shrimp shells waste by thermochemical or enzymatic methods. However, application of ultrasonic irradiation for chitin deacetylation has received little attention. In this work, the deacetylation of chitin with concentrated sodium hydroxide was performed using ultrasound irradiation (80 W, 42 kHz). The reaction time and degree of deacetylation were compared with conventional process. Results showed that under the same condition, the degree of deacetylation was similar. However, the use of ultrasonic irradiation decreased the reaction time, showing that this method may be a promising alternative method to the conventional method.

Abstract: Smart hydrogels which can change their swelling behavior and other properties in response to environmental stimuli such as temperature, pH, solvent composition and electric fields, have attracted great interest as chemical sensor material and controlled release system. The pH stimulus responsive hydrogels were synthesized by gamma-irradiation graft copolymerization of chitosan-acrylamide. In this research the influence of deacetylation process on the hydrogels characterization were investigated by measuring grafting efficiency, gel fraction, swelling degree, and crosslink density. Evidence of grafting was confirmed by FTIR spectroscopy. X-ray diffraction showed reduction in the crystallinity of chitosan with different deacetylation process also after the graft copolymerization reaction. The results showed that decreasing acetyl group of chitosan increase the grafting efficiency, gel fraction and swelling degree. While crystallinity decreased. The hydrogels indicated pH-dependent swelling behaviour.

Abstract: Treatment of protected furanoses with FeCl₃·6H₂O in acetonitrile with microwave irradiation provides an efficient and mild protocol for regioselective removal of anomeric O-acetyl group. This method features cost efficient reagents, simple procedures, and high yields. The experimental results proved that microwave irradiation could notably shorten the reaction time and increase the product yield compared to the conventional thermal heating condition.

Abstract: A novel and efficient method for the preparation of α-D-mannose-1-phosphate has been developed. Phosphitylation of tetraacetylated D-mannose, hydrolysis yielded H-phosphonate monoester. Silylation of H-phosphonate, followed by oxidative coupling and hydrolysis gave protected D-mannose-1-phosphate. Finally, deprotection of tetraacetylated D-mannose-1-phosphate afforded D-mannose-1-phosphate in excellent yield.

Abstract: β-chitosan preparation from squid pens was carried out using aqueous NaOH with the ultrasonic assistance. Single factor experiments and L₉ (3⁴) orthogonal experiments were used to investigate the effect of three parameters (reaction time, concentration of NaOH and reaction temperature) on deacetylation of β-chitin. The optimal conditions for deacetylation of chitin were reaction temperature 80°C, reaction time 2 h and concentration of NaOH 50%. The optimal conditions allowed deacetylation degree of β-chitin from 71.32% to 92.91%. The β-chitosan from squid pens was confirmed by Fourier transform infrared spectroscopy. The antibacterial activities of the prepared β-chitosans again staphylococcus aureus (S. aureus) and Escherchia coli (E.coli) were then determined and compared by the MIC (minimum inhibitory concentration). Results indicate that β-chitosans with different degrees of deacetylation (DD) possess different antibacterial activity. The growth of S. aureus can be easily inhibited by prepared β-chitosan than E.coli.

Abstract: Konjac glucomannan (KGM) were modified by deacetylation with sodium hydroxide, calcium hydroxide, sodium carbonate, sodium phosphate, respectively and mechanical properties of modified KGM films were investigated. The modification mechanism was explored by FTIR. Results show that deacetylation of KGM play an important role on the flexibility of the modified membranes, and the flexibilities vary with different modifiers. The flexibility of the films modified by sodium hydroxide is significantly higher than that of the others. The modified films with good flexibility were prepared by simple steps as follows: NaOH modifiers and KGM (1%) were added to water, stirred until the pH arrived at 9. And then the KGM swelled at the temperature of 50°C for 2 hours, the modified KGM sol was cast onto glass plates, the modified membranes were formed after dried at 50°C.