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

Abstract

Graphical abstractResearch Highlights: Semi-crystalline Fe-BTC MOF material is an efficient support for enzymes  It can be used by either in-situ or post-synthesis approaches  The in-situ (one-step) biocatalysts are more active and have lower enzyme leaching  This enzyme support improves the benefits given by some other MOF-based supports ABSTRACT. 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 postsynthesis 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 minutes); (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 postsynthesis approaches.

Efficient One-Step Immobilization of CaLB Lipase over MOF Support NH2-MIL-53(Al)

“…Apart from our own studies using nanocrystalline NH 2 -MIL-53(Al) supports for enzymes [20,21], the MIL-53(Al) family has proved to be efficient in the immobilization of: (i) Laccase on NH 2 -MIL-53(Al), using our one-step room-temperature methodology [37]; (ii) laccase on meso-MIL-53(Al) by post-synthesis methods [38]; and (iii) luciferase on non-functionalized MIL-53(Al), also by post-synthesis methodology [39]. We also found excellent results for lipase in situ immobilization on the semi-crystalline support Fe-BTC [23], suggesting that this enzyme could be easily immobilized onto MOF supports. In spite of the fact that Fe-BTC resulted in an excellent support for lipase, it is worth investigating any other MOF-based support for this enzyme such as the NH 2 -MIL-53(Al) considered in this work.…”

“…Amongst the numerous potential applications of MOFs, their use as enzyme supports has awakened the interest of the scientific community in the past few years [10][11][12][13][14][15][16][17], particularly since the intrinsic pore size of MOFs does not have to be necessarily larger than the enzyme size [18][19][20][21][22][23][24].…”

“…Moreover, they possess very high external surface areas [29] that favour their interaction with any macromolecules (for instance, enzymes). This fact, together with the natural chemical affinity of the enzyme for the MOF [18], makes the in situ approach for enzyme immobilization onto MOF-based supports a very efficient method [19][20][21][22][23][24]. Furthermore, immobilization is presumably non-covalent, so minor activity loss against that of the free enzyme could be reached.…”

“…On one hand, this support has a crystalline-enough structure that allows to properly understand the lipase-MOF interaction and, on the other hand, it is basically inert from a catalytic point of view. In addition, employing NH 2 -MIL-53(Al) support for lipase immobilization allows extending the state-of-the-art over a previous immobilization approach [21][22][23]. Different in-solution deprotonating agents such as sodium hydroxide (NaOH), triethylamine (TEA), or ammonium hydroxide (NH 4 OH) are studied here for generating lipase-based solid biocatalysts with NH 2 -MIL-53(Al) as the crystalline support.…”

Laccase Encapsulation in ZIF‐8 Metal‐Organic Framework Shows Stability Enhancement and Substrate Selectivity

“…Recently, nanocrystalline MOFs were used for the immobilization of laccases. Thereby, in the most successful cases post‐synthesis immobilization (PSI) was applied . An exception to PSI was the work by Patil et al.…”