Chimioselective Esterification of Wood Sterols with Lipases

3 Chimioselective Esterification of Wood Sterols with Lipases 

Esterases (EC 3.1) are a subclass of enzymes that catalyze the hydrolysis of esters to carboxylic acids and alcohols. Carboxylic ester hydrolases (EC 3.1.1) 

Microbial lipases are produced mostly by submerged fermentation. Many studies have been undertaken to define the optimal culture and nutritional requirements for lipase production. Lipase production is strongly influenced by a wide range of fermentation parameters such as nitrogen and carbon sources, pH, temperature, agitation, dissolved oxygen concentration and presence of lipids (Elibol and Ozer 2001). A survey of fermentation conditions for the production of bacterial lipases has been reported by Gupta et al. (2004). 

Other fermentation parameters, such as temperature, pH, agitation and aeration rate are important in microbial hpase production. These parameters are strain dependent bacteria prefer neutral pHs and the optimum temperature for lipase production corresponds with the growth temperature of the respective organism, which is in the 20-45 °C range, although in some cases optimum temperatures outside that range have been reported Sharma et al. (2002). 

Most commercial applications, such as enzyme preparations for detergents, do not require pure lipases, but a certain degree of purity simplifies their successfiil usage as biocatalysts because reduces side-product formation and simplifies product downstream. Extensive lipase purification should be considered when structural studies are going to be performed or when it will be used as biocatalyst in a synthetic reaction for the pharmaceutical industry. The main drawbacks of traditional purification strategies are low yields and productivities. The extent of purification varies with the number and the order of purification steps (see section 2.2.3) the importance of designing optimal purification schemes has been highlighted in several comprehensive reviews on this topic (Taipa et al. 1992 Aires-Barros et al. 1994 Palekar et al. 2000 Saxena et al. 2003). 

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