Hydrolysis of olive oil catalyzed by Candida lipolytica lipase was investigated. The relative concentration of the components in the product was determined by using high performance liquid chromatography（HPLC）. Furthermore, a novel rapid method to detect the hydrolytic process of olive oil was developed based on the relationship between the acid value and the relative concentration of the different components.
GAO Gui ZHENG Liang-yu ZHANG Zuo-ming HAN Si-ping CAO Sui-gui
A simple method for rapid estimation of the enantioselectivity of lipase in resolution of chiral esters is described. The enantioselectivity of lipase can be estimated rapidly through comparing the difference of hydrolysis rates for the racemic ester and its slow reacting enantiomer under the same condition because the difference mainly depends on the enantioselective ratio（E values）. The higher the enantioselectivity of enzyme, the larger the difference of hydrolysis rate. The bromothymol blue（BTB） can be used as pH indicator for microplate reader to monitor the formation of acid in lipase-catalyzed hydrolysis of esters. This method has been successfully used to rapidly estimate the enantioselectivity of several lipases in the resolution of glycidyl butyrate.
WANG PingWANG LeiWANG Li-chengLI Chun-yuanWANG RenMIAO Qing-huaYANG MingWANG Zhi
A novel preparation method was developed to form a surfactant-lipase complex for the resolution of 2-octanol in a solvent-free system. The E value was improved from 6.64 to 120.2. The lipase modified by the anionic surfactant possessed a low solubility in the solvent-free system, which was beneficial to the recovery and the repeated usage of the lipase. The surfactant-lipase complex maintained a high enantioselectivity after five cycles of usage. The effect of water on both the activity and the enantioselectivity of the lipase has also been investigated; the direct addition of a salt hydrate pair of Na 4P 2O 7·H 2O and Na 4P 2O 7 can dramatically activate the modified enzyme.
The lipases from different sources were screened for their ability to catalyze the resolution of 2-octanol in organic solvents with vinyl acetate as the acylating reagent. The medium effect has been studied on the irreversible transesterification with varying water activity(a_w). The influence of vinyl acetate concentration on it has also been investigated. Under the optimal conditions, the enantiomeric ratio(E value) of pseudomonas fluorescence lipase(PFL) exceeded 200 with an enantiomeric excess(e.e.) of S-2-octanol above 99% at a 51% degree of conversion.
The changes in the activity and the conformation of the hyperthermophilic esterase derived from aerobic thermophilic Aeropyrum pernix K1 （ APE1547 ） were studied during denaturation by guanidine hydrochlofide （ GdnHC1 ） and urea. The denaturation course of APE1547 was followed by the steady-state and time resolved fluorescence methods. An increase in the denaturant concentration in the denatured system can significantly enhance the inactivation and unfolding of APE1547. The enzyme can be completely inactivated with a urea concentration of 2.7 mol/L or a GdnHCl concentration of 7.5 mol/L. The fluorescence emission maximum of the enzyme protein red shifts in magnitude to a maximum value（355 nm） when the concentration of GdnHCl is 5.1 mol/L. The experimental results indicate that APE1547 has a high resistance to urea. Unfolding of APE1547 in GdnHCI（4. 2-6.0 mol/L） was shown to be an irreversible process. The present results indicate that the ion pairs in this protein may be a key factor for the stability of this esterase.
