Covalent immobilization of soybean seed hull urease on chitosan mini-spheres and the impact in their properties

BRACCO, LAUTARO F.; LEVIN, GUSTAVO J.; NAVARRO DEL CANIZO, AGUSTIN A.; WOLMAN, FEDERICO J.; MIRANDA, MARÍA V.; CASCONE, OSVALDO

Biocatalysis and agricultural biotechnology

Elsevier

Lugar: Amsterdam; Año: 2019 vol. 18

1878-8181

Urease is found in bacteria, fungi, algae, plants and some invertebrates, and in soils. In plants, it is present in most of Leguminosae seeds, accounting for 0.2-0.3 % of the extractable soybean seed protein, being also present in the hulls, in lesser amounts. Soybean hull is a low-cost agro-industrial waste from the soybean manufacturing process. In a way of exploiting its possible applications, urease was immobilized on thiolated chitosan mini-spheres through its sulphydryl groups. Almost quantitative immobilization from a crude extract of seed hull soybean was obtained. After 4 h at 70° C, the activity of free soybean hull urease (SBU) was 50 % lower than that of the immobilized enzyme. The pH of maximum activity shifted from 7 to 5 after immobilization, thus allowing its use in processes performed at acid pH. The immobilization brought about an increase in the optimum activity temperature from 65° C to 75° C. An 84 % of the activity of the immobilized SBU was retained after 25 cycles of utilization, and the activity was maintained after 90 days at 4° C. The immobilized enzyme was employed with success in the measurement of urea in serum.