ISEL - Eng. Quim. Biol. - Artigos
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Browsing ISEL - Eng. Quim. Biol. - Artigos by Author "Abdelmoez, Wael"
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- Optimisation and economic assessment of lipase-catalysed production of monoesters using Rhizomucor miehei lipase in a solvent-free systemPublication . Ahmad, Mustafa; Karmali, Amin; Abdelmoez, WaelEnzymatic production of glycerin monolaurate (GML) was carried out by lipase catalysed esterification of lauric acid and glycerin in a solvent-free media. Response surface methodology (RSM), based on 5-level and 3-variable composite design, was employed to study the interactive effects of reaction temperature (48-60 degrees C), enzyme load (1-4% w/w), and glycerin to lauric acid molar ratio (1:1-4:1) on glycerin laurate yield. The optimum conditions obtained were a temperature of 60 degrees C, an enzyme load of 4%, and a glycerin to lauric acid molar ratio of 4:1. The maximum predicted and experimental conversion values were 92.26% and 93.23%, respectively. Utilisation of Lipozyme RM IM (Rhizomucor miehei lipase) allowed the formation of a mixture consisting of 50% monoglyceride, 34.6% diglyceride and 8A% triglyceride, which fulfills the requirements established by the World Health Organization (WHO) for use as a food emulsifier. In addition, the Lipozyme RM IM maintained more than 90% of its original activity after being used for six cycles. Finally, an economic study was performed to interrogate the feasibility of the proposed enzymatic manufacturing process. The obtained results were Compared with the traditional catalysed chemical process. The economic feasibility study revealed that the needed amount of Lipozyme RM IM was 2.5 kg/t of feedstock. The high conversion achieved in a short reaction time (1 h), as well as the proven operational stability of Lipozyme RM IM, revealed a promising potential for this green and sustainable route in practical applications.
- A sensitive microplate assay for lipase activity measurement using olive oil emulsion substrate: modification of the copper soap colorimetric methodPublication . Mustafa, Ahmad; Karmali, Amin; Abdelmoez, WaelThe present work involves a sensitive high-throughput microtiter plate based colorimetric assay for estimating lipase activity using cupric acetate pyridine reagent (CAPR). In the first approach, three factors two levels factorial design methodology was used to evaluate the interactive effect of different parameters on the sensitivity of the assay method. The optimization study revealed that the optimum CAPR concentration was 7.5% w/v, the optimum solvent was heptane and the optimum CAPR pH was 6. In the second approach, the optimized colorimetric microplate assay was used to measure lipase activity based on enzymatic hydrolysis of olive oil emulsion substrate at 37°C and 150 rpm. The emulsion substrates were formulated by using olive oil, triton X-100 (10% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 1:1:1 in the case of Candida sp. lipase. While in the case of immobilized lipozyme RMIM, The emulsion substrates were formulated by using olive oil, triton X-100 (1% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 2:1:1. Absorbance was measured at 655 nm. The stability of this assay (in terms of colored heptane phase absorbance readings) retained more than 92.5% after 24 h at 4°C compared to the absorbance readings measured at zero time. In comparison with other lipase assay methods, beside the developed sensitivity, the reproducibility and the lower limit of detection (LOD) of the proposed method, it permits analyzing of 96 samples at one time in a 96-well microplate. Furthermore, it consumes small quantities of chemicals and unit operations.