Effect of biopolymer matrices on lactose hydrolysis by enzymatically active hydrogel and aerogels loaded with β-galactosidase nanoflowers

In this work, enzymatically active polysaccharide-based hydrogels and aerogels have been developed. To this end, a thermostable β-galactosidase (TmLac) enzyme from Thermotoga maritima embedded in nanoflowers’ format was used to evaluate the capacity of the hydrogel matrices to preserve the hydrolytic activity of the enzyme and the reusability of the hydrogels formed. Commercial agar, unpurified agar and agarose were compared as supporting materials. Although the developed hydrogel capsules can be used at high temperature (75 °C) and reused for the digestion of lactose to a greater extent than the free nanoflowers, loaded hydrogel capsules behaved differently depending on the type of polysaccharide used. Commercial agar was the most promising one since these hydrogel capsules could be reused, maintaining the structural integrity and reaching higher enzymatic activity (after seven cycles at 75 °C) than the free TmLac-Ca2+ nanoflowers. To facilitate handling and storage, aerogels were developed by freeze-drying the hydrogel capsules. Aerogels of agarose and unpurified agar underwent structural changes during freeze-drying that adversely affected their subsequent use, losing their integrity after being rehydrated. However, commercial agar aerogels were successfully developed and reused thanks to the existing interactions with TmLac-Ca2+ nanoflowers (confirmed by FTIR), which resulted in better capsule integrity and enzyme protection. The hydrolytic activity of enzymatically active aerogels based on commercial agar was in the same range of the free TmLac and TmLac-Ca2+ nanoflowers, being significantly higher to their counterparts in the hydrated form (hydrogels based on commercial agar).This research was supported by grants from Spain's ‘Secretaría de Estado de Investigación, Desarrollo e Innovación' (AGL2016-75245-R), Agencia Estatal de Investigación (AEI, Grant PCI2018-092886) and cofunded by the European Union's Horizon 2020 research and innovation programme (ERA-Net SUSFOOD2). MJF was supported by a Ramon y Cajal contract (RYC2014-15842) from the Spanish Ministerio de Economia; Industria y Competitividad.Peer reviewe