Tailoring of alginates by enzymatic modification in vitro

High molecular weight alginates having a variety of initial composition and sequential structures were modified with a mannuronan-C-5 epimerase from Azotobacter vinelandii to yield polymers with a high content of guluronic acid and, hence, an enhanced ability to form gels with calcium ions. The monad, diad and triad frequencies in the modified polymers were determined by n.m.r. spectroscopy, and the strength of homogeneous gels prepared from them with calcium ions were measured and compared with those prepared from the starting materials and other naturally occurring alginates. Immobilization of the bacterial enzyme on Eupergite beads greatly increased its stability and favoured high degree of conversion.