Notions of Convexity
The first two chapters of this book are devoted to convexity in the classical sense, for functions of one and several real variables respectively. This gives a background for the study in the following chapters of related notions which occur in the theory
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ORIGINAL ARTICLE
Extracellular lipase of Aspergillus terreus var. africanus (CBS 130.55): production, purification and characterisation Hossam S. Hamdy & Medhat A. Abo-Tahon
Received: 28 November 2011 / Accepted: 6 February 2012 / Published online: 29 February 2012 # Springer-Verlag and the University of Milan 2012
Abstract An extracellular lipase was optimally produced by Aspergillus terreus var. africanus (CBS 130.55) after 4 days of submerged fermentation at 30°C, initial pH 6, agitation rate of 150 rpm, using COO(NH4)2H2O, olive oil and K2HPO4 as nitrogen, carbon and phosphorous sources, respectively. The enzyme was purified to electrophoretic homogeneity and its maximum activity was recorded at pH 7 and 35°C and was stimulated by Ba+2, Mg+2 and Na+1. Sugars, polyhydric alcohols and metal ions enhanced the enzyme’s thermal stability. In the presence of 10 mM glucose or Ba2+, Tm (midpoint of thermal inactivation) was recorded at 57°C and 60°C after 60 min, respectively, while T1/2 were found to be 17 and 13 weeks at 4°C or −15°C, respectively. Molecular mass, Vmax, Km and Kcat of the enzyme were found to be 42.5±0.9 kDa, 63.10 mM ml−1 min−1, 0.85 mM, and 1.62 mM ml−1 min−1, respectively. Possible participation of the SH group in the purified lipase was suggested and its glycoprotein nature was confirmed. The purified enzyme showed a reasonable stability with some commercial detergents. Keywords Aspergillus terreus . Lipase production . Enzyme purification and characterisation . Thermal stability . Compatibility with detergents
H. S. Hamdy (*) : M. A. Abo-Tahon Biological Sciences & Geology Department, Faculty of Education, Ain Shams University, Roxy, Heliopolis, Cairo 11757, Egypt e-mail: [email protected]
Introduction Lipases (triacylglycerol acylhydrolases, EC 3.1.1.3) hydrolyse tri-, di- and monoglycerides at an oil–water interface and the majority of lipases exhibit a high activity toward lipids with fatty acid residues of C8 to C18 chain length (Dixon and Webb 1979). Lipases have become an integral part of the modern food and beverage industry, and are used in flavour development for dairy products, the lipolysis of butter, fats and cream (Stecher and Faber 1997). Moreover, they are used as emulsifiers in the food, pharmaceuticals, cosmetics and perfumery industries as well as for the production of maltose- and lactose-like sugar fatty acid esters (Sharma et al. 2011). Lipases are used in manufacturing lipid biosensors used as clinical diagnostic tools and in the food industry (Benjamin and Pandey 2001). Lipases can reduce the environmental load of detergent products since they are biodegradable, save energy by enabling a lower wash temperature, have no negative impact on sewage treatment processes, and do not present a risk to aquatic life (Falch 1991). They have an important application in bioremediation by handling and removing oil spills, degrading wastewater contaminants with oil and purifying the waste gases from factories (Nakamura et al. 1994). Lipases play a role in the industry of surfactan
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