No abstract

No abstract

Esters of fatty acids (FAs) and polyethylene glycol 400 (PEG) are valuable chemically derived surfactants. In this work, it is shown that the chemical synthesis of PEG esters can be replaced by enzymatic synthesis under milder conditions and using simpler and more environmentally friendly technology. The main obstacles to enzymatic catalysis in a system of PEG and higher FAs are the high viscosity of the former and the low water solubility of the latter. These problems are solved by selecting organic media and other con ditions of the process mediated by pancreatic lipase. The optimum conditions for the synthesis of PEG esters of FAs are determined: reaction medium, benzene/hexane in a ratio of 2 : 3; optimum temperature, 25°C; water content in the system, no more than 0.2%; FA : PEG molar ratio, 1 : 1.8; reaction time, 48 h. Under these conditions, the yields in synthesizing PEG esters of capric, lauric, and palmitic acids are 80, 78, and 44%, respectively.

Main applications of lipases for the production of esters with different structures are analyzed in the review. The effect of nonaqueous media, methods of lipase immobilization, and substrate specificity on enzymatic esterification is described. Implementations of enzymatic esterification reactions under industrial conditions using two configurations of reactors – with fixed or fluidized bed – are reported. Esters obtained by enzymatic catalysis are systematized with respect to their chemical structure. Lipases are shown to be promising for use in the esterification processes aimed to produce esters with different structures and intended for various purposes.

The target size of NADH-oxidase activity of M. lysodeikticus isolated membranes for electron radiation is nearly equal to that obtained for NADH-dehydrogenase (about 50 kD). The complete cross-linking of membrane proteins by glutaraldehyde causes an increase of NADH-oxidase target size to 3-3.5 times its original value. Electrons are transported by cross-linked respiratory chain from NADH to O2 with 60-50% effectiveness of that in untreated membranes. It is proposed that electrons are transported through a multi-enzymic complex of individual carriers having limited lifetime with exchange of carriers between different respiratory complexes via lateral diffusion in membrane.