Lipases (triacylglycerol acylhydrolase, EC 3.1.1.3) are part of the family of hydrolases that act on carboxylic ester bonds. The physiologic role of lipases is to hydrolyze triglycerides into diglycerides, monoglycerides, fatty acids, and glycerol. These enzymes are widely found throughout the animal and plant kingdoms, as well as in molds and bacteria. Of all known enzymes, lipases have attracted the most scientific attention. In addition to their natural function of hydrolyzing carboxylic ester bonds, lipases can catalyze esterification, interesterification, and transesterification reactions in nonaqueous media. This versatility makes lipases the enzymes of choice for potential applications in the food, detergent, pharmaceutical, leather, textile, cosmetic, and paper industries. The most significant industrial applications of lipases have been mainly found in the food, detergent, and pharmaceutical sectors. Limitations of the industrial use of these enzymes have mainly been owing to their high production costs, which may be overcome by molecular technologies, enabling the production of these enzymes at high levels and in a virtually purified form.
The thermostable esterase from the moderate thermophile Bacillus circulans was purified to homogeneity using a four-step procedure. Esterase activity was associated with a protein of molecular mass 95 kDa, composed of three identical subunits of 30 kDa. The esterase activity was thermostable with a maximum activity at 55 degrees C using initial rate assay. The half-inactivation temperature was 71 degrees C after a 1-h treatment, which compared favorably to that of other enzymes. Activity at temperatures of 30-37 degrees C was high (about half of maximum), making this new enzyme very attractive for applications in this moderate temperature range. The esterase also showed high activity at a rather alkaline pH (higher than 10). The specificity pattern showed a marked specificity for mid-chain-length fatty acids (3-8 carbon atoms), which classified the enzyme as a carboxylesterase.
Growth and ethanol production by three strains (MSN77, thermotolerant, SBE15, osmotolerant and wild type ZM4) of the bacterium Zymomonas mobilis were tested in a rich medium containing the hexose fraction from a cellulose hydrolysate (Aspen wood). The variations of yield and kinetic parameters with fermentation time revealed an inhibition of growth by the ethanol produced. This inhibition may result from the increase in medium osmolality due to ethanol formation from glucose.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.