Enzymatic reactions of polar steryl conjugates

Project abstract

Plant sterols are functional food ingredients, which have gained significant interest owing to their cholesterol lowering function. The wide range of different plant sterols and their conjugates are, however, not fully exploited by the food industry, as the polar conjugates, namely steryl ferulates and steryl glycosides, are not yet abundantly used in food applications. The more polar characteristics and functional groups in the conjugated molecules give them additional health benefits and physical functions, which could be better utilized, if these ingredients were available more abundantly. On the other hand, some industrial processes, like the biodiesel production, suffer from the precipitation of
steryl glycosides, and would greatly benefit form their enzymatic hydrolysis.

The greatest difficulty in the enzymatic synthesis and hydrolysis of steryl ferulates and steryl glycosides is the poor knowledge over the factors that govern the enzymatic interconversions. In particular, there is an enormous gap in the knowledge over the enzymes that are capable of acting on sterol substrates, the reaction conditions that decide the direction of the reaction, as well as the specificities of the enzymes towards different sterols and the different conjugated compounds. This project aims to (i) identify the enzymes that are responsible for sterol conjugation and sterol conjugate hydrolysis, (ii) define the optimal conditions for each of the reactions, and (iii) characterize the properties of the steryl conjugates as functional food ingredients. The two major outcomes of the project are methods to tailor polar sterol
ingredients to foods, and a solid understanding over their hydrolytic reactions at processing conditions and in humans after food consumption.