Reusability study of Novozym® 435 for the enzymatic synthesis of mannosyl myristate in pure ionic liquids

Abstract

When developing a biocatalyzed synthesis route, the enzyme reusability is an important parameter to consider for the reduction of industrial costs. In this context, the functional stability of Novozym® 435 in ionic liquids (ILs) was studied in the transesterification of mannose with vinyl myristate. The enzyme was re-used five times in three ILs, 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim][TFO]), 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([Bmpyrr][TFO]) and in tert-butanol (tert-BuOH). [Bmpyrr][TFO] showed the best 24 h-yield (24 h-η), with 68.8% after the first cycle and the lowest loss of 24 h-η (42%) after five cycles (24 h-η of 39.9%). In comparison with [Bmpyrr][TFO], Novozym® 435 presented the most prominent loss of activity after five cycles of reaction in [Bmim][TFO] (loss of 89%), despite the good 24 h-η obtained after one cycle (60%). [Bmim][BF4] was the least interesting IL, as it was found to lead to the lowest 24 h-η, with 24.5% after one cycle and a significant loss of activity (77%) after five cycles, with a 24 h-η of 5.6%. After five cycles, the 24 h-η in [Bmpyrr][TFO] was higher than in tert-BuOH and the yield loss was higher for the organic solvent (57%). Consequently, these results reveal that, in the present study, the pyrrolidium-based IL [Bmpyrr][TFO] represented the best IL as it allowed the highest level of enzymatic activity and functional stability of Novozym® 435.

Keywords

• Esters
• carbohydrates
• esterification
• lipases
• enzyme technology