Semi-crystalline Fe-BTC MOF material as an efficient support for enzyme immobilization

Metal-organic frameworks (MOFs) have revolutionized the potential applications of nanoporous materials. One of the most recent and promising applications of these materials is their use as supports for enzyme immobilization. In this context, the in-situ (one-step) methodologies, which do not require the use of MOFs with pores larger than the enzyme to be immobilized, seem to be particularly encouraging. This work presents a systematic study of the semi-crystalline Fe-BTC MOF material (commercialized as Basolite F300) employed as support of the enzymes laccase and lipase through either in-situ or post-synthesis methodology. The presence of the enzyme in the resultant solid biocatalysts was proved by CHNS chemical analysis, thermogravimetric analysis, Bradford assays and by SDS-PAGE electrophoresis. The enzymatic activity of the resultant Fe-BTC-based biocatalysts was also tested. The in-situ approach is particularly relevant due to various reasons: (i) the enzyme immobilization is given in one step; (ii) it is rapid (10 min); (iii) it is very efficient in terms of encapsulation capacity (≥98% for laccase and ≥87% for lipase); (iv) the enzymes are fully retained and no leaching is observed after an initial release of only around 10% of the enzyme molecules weakly immobilized; and (v) the activity of the retained enzyme can be substantially maintained (97% with respect to the free enzyme in the case of lipase). Any of these parameters systematically improves these given by the post-synthesis (two-step) approach. Moreover, Fe-BTC widely surpasses the benefits given by other MOF-based supports either by in-situ or post-synthesis approaches.