Electrospun PVA fibrous mats immobilizing lipase entrapped in alkylsilicate cages: Application to continuous production of fatty acid butyl ester

Electrospun polyvinyl alcohol (PVA) fibers are used to immobilize lipase entrapped in organosilicate cages. The cages are prepared from dimethyldimethoxysilane and tetramethoxysilane (called Fiber-SilicaLip in this paper) and are used as the active component of a flow-through reactor for the continuous production of fatty acid butyl esters by butanolysis of rapeseed oil. The catalytic activity of the catalyst, defined by reaction rate during the first 4 h of reaction, depended on the content of water in the mixture of rapeseed oil and n-butanol (molar ratio of triglyceride and n-butanol = 1:3). The highest catalytic activity was detected at 0.5% (w/w) water addition. At this level, Fiber-SilicaLip showed a 57-fold increase in catalytic activity over purchased lipase powder and 3.7-fold higher catalytic activity than PVA fibers enclosing non-treated lipase. In addition, the reaction rate per amount of catalyst (matrix + protein lipase) detected at 0.5% (w/w) water addition was 1.6 times greater than the maximum value detected for Novozym 435 with no added water. The Fiber-SilicaLip continued to work as a catalyst for a 14 day run as a membranous component of a continuous fatty acid butyl esters production system.