Crude Urease Extract for Biocementation

Abstract

A crude extract from jack beans (Canavalia gladiata) is demonstrated to be an effective source of urease enzyme for biocementation via enzyme-induced carbonate precipitation (EICP). Test tube tests of crude and purified extracts from jack beans, jack bean meal, soybeans, and watermelon seeds show that the crude jack bean extract results in the highest unit yield, defined as urease content per initial mass of source material, among these four plant sources. The efficacy of EICP using crude jack bean extract for biocementation was compared with the efficacy of three commercially available enzymes by biocementation of a granular soil. Unconfined compression tests on the granular soil specimens subject to biocementation via EICP demonstrated that the crude extract and the less purified commercially available enzyme were actually more effective than commercially available highly purified urease enzymes at enhancing soil strength, an effect attributed to the presence of complementary proteins in the less purified enzyme sources. The simple technique used to produce the crude extract from jack beans significantly lowers the cost of EICP, eliminating a major barrier to practical applications, including infrastructure construction and environmental protection.