Preparation of multipurpose cross-linked enzyme aggregates and their application to production of alkyl ferulates

Commercial multicomponent enzyme preparations, Ultraflo L, Depol 740L and Depol 670L, with feruloyl esterase activity, were tested for the transesterification of methyl ferulate to 1-butyl ferulate in their free and immobilized form using as a reaction system a ternary water–organic mixture consisting of n-hexane, 1-butanol and water. A number of factors affecting enzymes precipitation and cross-linking into cross-linked enzyme aggregates (CLEAs) have been investigated. Consecutive optimization of the precipitant type and cross-linker concentration resulted in CLEAs showing higher operational stability and synthetic activity compared to the free enzymes’ forms. Under certain optimization conditions, conversion yields of 97%, 87% and 5%, were obtained by CLEAs prepared from Ultraflo L, Depol 740L and Depol 670L, respectively. The activities initially present in the three commercial preparations were completely retained after cross-linking resulting in multipurpose biocatalysts which have the potential to carry out different and independent reactions. This work is consistent to the novel CLEA concept called combi-CLEA.