A high efficiency method combining metal chelate ionic liquid-based aqueous two-phase flotation with two-step precipitation process for bromelain purification.

This work was to develop a cost-effective and sustainable method which included metal chelate ionic liquid-based aqueous two-phase flotation (IL-based ATPF) and a two-step precipitation process for purifying bromelain from pineapple. Firstly, the metal chelate IL-based ATPF with a copper chelate-functionalized thermosensitive block copolymer (L64-IDA-Cu(II)) as trapping agent was used as the primary purification to obtain the L64-IDA-Cu(II)-bromelain complex. Secondly, the two-step precipitation process based on the thermosensitive properties of the L64-IDA-Cu(II) was mainly carried out to achieve the further purification of bromelain. According to a series of optimal experiments, the enzymatic activity recovery of final bromelain was 95.22 ± 0.04%, and the purification factor reached 6.56 ± 0.03. The results of recycling of ILs and the trapping agent were satisfactory. Furthermore, the conclusions of comparison with other methods proved the superiority of this method. This novel recycling purification method has a goodindustrial prospect in future.