Title : Preparation and application of modified loofah sponges for metal chelation, protein purification, and enzyme immobilization
The applications of modified loofah sponges for the removal of heavy metals from wastewater, the selective adsorption of His-tagged enzyme, and the integrated approach for the adsorption and immobilization of enzymes from unclarified cell homogenate will be discusses. Loofah sponge is the fibrous vascular reticulated system of the matured dried fruit of Luffa cylindrica. The conjugation of iminodiacetic acid to epichlorohydrin-activated loofah sponge was found to increase the metal chelation capacity by ca. 220% from 11.6 ± 0.017 mg/g to 37.9 ± 0.277 mg/g. Upon the grafting of hydroxyethyl cellulose, the adsorption capacity of the loofah sponge-based immobilized metal affinity adsorbent for His-tagged trehalose synthase was increased by ca. 60% from 1.51 mg/g to 2.45 mg/g. Similar results were also observed for delignified loofah sponge prepared by sodium chlorite-acetic acid pretreatment. Both the adsorption isotherms of the hydroxyethyl cellulose-grafted and the delignified loofah sponges followed the Langmuir isotherm model with dissociation constants, Kd, in the range of 10-6M. Bifunctional loofah sponge-based adsorbent with metal chelate groups for the selective adsorption of His-tagged proteins and epoxy groups for the subsequent covalent immobilization of the adsorbed proteins was prepared by partial iminodiacetic acid conjugation of epichlorohydrin-activated loofah sponge. Bifunctional loofah sponge-based adsorbent with an [epoxy groups]/[metal chelate groups] ratio of 0.75 exhibited both a protein adsorption capacity of 0.639 mg/g and an immobilization yield of 93%. The immobilized enzyme thus prepared exhibited superior operational stability in repeated-batch processes, retaining 96% of its initial activity after 20 cycles. The employment of the bifunctional loofah sponge can significantly facilitate the preparation of immobilized enzymes by consolidating protein purification and enzyme immobilization.
Audience Takeaway Notes:
- The diverse utilities of loofah sponge for biocatalysis, biosepartions, and wastewater treatment.
- The enhancement of metal chelating and protein adsorption capacities by hydroxyethyl cellulose grafting and delignification of loofah sponge.
- The potential of loofah sponge-based immobilized metal chelate adsorbents for the selective adsorption of His-tagged proteins from unclarified cell homogenates.
- The integrated approach for the purification and immobilization of His-tagged enzymes with metal chelate-epoxy bifunctional loofah sponge-based adsorbents.