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Lysozyme crystals in the presence of 1-butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim]BF(4)), 1-butyl-3-methylimidazolium chloride ([C(4)mim]Cl), 1-butyl-3-methylimidazolium bromide([C(4)mim]Br), and 1,3-dimethylimidazolium iodine([dmim]I) were prepared, and the influence of ionic liquids (ILs) on the structure and activity change of lysozyme was investigated. Fourier transform infrared spectroscopy revealed the major secondary structures of α-helix and β-sheet for lysozyme. It was interesting to note that increases of the band near 2,935 and 1,656 cm(-1) from Raman spectroscopy are attributed to the unfolding of lysozyme molecules. A shift in amide III from 1,230 to 1,270 cm(-1) in adding [dmim]I occurs, indicating a transformation from β-sheet to random coil. With regard to adding [C(4)mim]BF(4), [C(4)mim]Cl, and [C(4)mim]Br, α-helix and β-sheet are the predominant structures for lysozyme. The activity study showed that the ILs used brought a positive effect. Especially, [dmim]I leads to a drastic increase in relative activity, and its value reaches 50 %.

Understanding the salting effects on the solubility and transformation kinetics of amino acid solvates in aqueous solutions is important for a rational design of the industrial isolation and purification conditions of amino acid. We report measurements of L-phenylalanine anhydrate and monohydrate solubility as a function of temperature in aqueous NaCl, KCl, Na 2 SO 4 , and (NH 4 ) 2 SO 4 solutions with concentrations of 4 g/100 g of H 2 O in this work. It is found that salts play an important role in determining solubility reduction and solvated behavior, which had not been elucidated. This comparison has provided important insight into the dependence of L-phenylalanine solvates on temperature. The dependence of the L-phenylalanine anhydrate/monohydrate transformation kinetics on temperature in the presence of NaCl, as a typical salt, is discussed. It is noted that NaCl can markedly increase the rate of the transformation of L-phenylalanine between anhydrate and monohydrate compared with pure water. A simple model for the transformation kinetics based on the salt effect between anhydrate and monohydrate is established, which can quantitatively provide the observed experimental dependence of the transformation rate on time. This work can provide important instruction for optimum process control during industrial production of L-phenylalanine.

This study investigated the microstructure and physicochemical properties of amylose and amylopectin fractionated from kudzu starch. Enzymolysis of the fractionated amylose and amylopectin with pullulanase revealed significant differences in the D-glucose chain structures. The amylose molecule had a lower degree of polymerization (DP n ), with fewer but longer glucose unit chains compared with the amylopectin molecule. The average external and internal chain lengths of amylopectin were 12.71 and 7.21, respectively. X-ray diffraction analysis of the crystalline structure of the starches showed that the amylopectin derived from kudzu starch was amorphous with no obvious diffraction pattern, whereas the amylose exhibited a superposition of the A and B type diffraction patterns, while the native starch exhibited typical C-type patterns. The amylose fraction exhibited a higher iodine affinity and lower swelling power (SP) than the native starch, which was likely due to the water holding capacity of the hydrogen bonds within the starch molecules. The amylopectin had a very high solubility, a particular characteristic of kudzu starch which may render it suitable for certain special industrial applications. Analysis of the thermal properties of the starches revealed that amylose had a higher melting enthalpy than amylopectin, which may be related to the helical structure and higher crystallinity degree of this fraction. Collectively, these results are likely to inform future developments in the practical application of kudzu starch by industry, and enable improvements to be made in the functionality of products incorporating this starch.

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