Novel microgel puts enzymes to work

Using biopolymers to take natural catalysts to industrial-scale reactions.

One of the main stumbling blocks to the widespread adoption of enzymes as natural catalysts in industrial-scale reactions has been the difficulty of extracting the enzyme after the reaction has finished. Now a team of US chemists has come up with a possible way around the problem by immobilising enzymes within a specially designed biopolymer microgel.

Developed by chemists from Carnegie Mellon University, Pittsburgh, the microgel is made up of Y-shaped constructs of DNA, formed from three partially complementary strands.

To get the constructs to form the microgel, the researchers attach the vitamin biotin to the end of each arm of the DNA construct. Adding the protein avidin, which can bind up to four biotin groups simultaneously, causes the DNA constructs to join together into a homogenous solution of cross-linked particles.

The microgel has two main properties that make it useful as an enzyme immobiliser. First, it is easy to incorporate a range of enzymes into the microgel by conjugating them with avidin. Second, although the microgel is a stable solution at around 35°C, at room temperature the microgel particles aggregate together and begin to precipitate out of solution, providing an easy way to retrieve the enzyme.

The researchers tested the potential of the microgel using the enzyme beta-galactidose, which is widely used in the dairy industry to hydrolyse lactose in milk. They discovered that not only did the enzyme work perfectly well when it was incorporated within the microgel solution, but that it retained its catalytic capability after the microgel particles to which it was attached had precipitated out of solution.

Jon Evans