Lipase@zeolitic imidazolate framework ZIF-90: A highly stable and recyclable biocatalyst for the synthesis of fruity banana flavour.

A zeolitic imidazolate framework (ZIF-90) has been synthesized through solvothermal method. The structure was characterized by means of FT-IR spectroscopy, X-ray diffraction, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS). The synthesized ZIF-90 was applied as a support for immobilization of porcine pancreatic lipase (PPL). The immobilized enzyme (PPL@ZIF-90) exhibited immobilization yield and efficiency of 66 ± 1.8% and 89 ± 1.4%, respectively. The pH and thermal stability of PPL was improved after immobilization and the initial activity was retained at about 57% after 20 days of storage at 4 °C for PPL@ZIF-90. Moreover, about 57% of the original activity was remained following 10 cycles of application. In Michaelis-Menten kinetic studies, Km value for PPL@ZIF-90 was lower, while, the Vmax was higher than free PPL. Moreover, optimized conditions to produce fruity banana flavour upon esterification of butyric acid were investigated. The optimum esterification yield was 73.79 ± 1.31% in the presence of 245 mg PPL@ZIF-90, alcohol/acid ratio of 2.78 and 39 h reaction time. PPL@ZIF-90 showed 39% relative esterification yield after six cycles of reuse. The results suggested that PPL@ZIF-90 can be used as a potential effective biocatalyst for synthesis of isoamyl butyrate.

Biodegradation of bisphenol A by the immobilized laccase on some synthesized and modified forms of zeolite Y.

Bisphenol A (BPA) is an environmental pollutant with adverse effects on different ecosystems. In this study, immobilized laccase enzymes onto inorganic supports were used to remove BPA. Laccase was successfully immobilized on sodium zeolite Y (NaY) and its modified desilicated (DSY) and dealuminated (DAY) forms. NaY-based supports were instrumentally characterized. The immobilized laccase on NaY (laccase@NaY), desilicated (laccase@DSY), and dealuminated (laccase@DAY) forms showed significant improvement on immobilization yield (IY%) and efficiency (IE%). Laccase@DSY and laccase@NaY showed IY% = 73.18 ±â€¯3.33 % and 46.23 ±â€¯1.81 % and IE% = 94.50 ±â€¯1.86 %, and 74.39 ±â€¯1.41 %, respectively, whereas IY% and IE% for laccase@DAY were achieved as 81.12 ±â€¯1.32 % and 98.56 ±â€¯2.93 %, respectively. The supports also increased the enzyme characteristics such as pH-temperature range, catalytic stability, and reusability. Km values were 0.73 ±â€¯0.05, 0.26 ±â€¯0.09, 0.31 ±â€¯0.5, and 1.01 ±â€¯0.03 mM for laccase@NaY, laccase@DAY, laccase@DSY, and the free enzyme, respectively. The enzyme demonstrated higher biodegradation ability of bisphenol A upon immobilization on the supports compared to that of the soluble enzyme. A bio-removal yield of 86.7 % was obtained considering three parameters including amount of laccase@DAY (8 U mg-1), concentration of BPA (0.5 mM), and treatment time (1 h) based on response surface methodology (RSM). Biodegradation metabolites (49 ±â€¯5.8 %) and unconverted BPA (14 ±â€¯5.2 %) were analyzed by gas chromatography-mass spectrometry.