Enzymatic synthesis, purification and identification of bioactive trehalose ester derivatives for health applications

• The Novozym 435 is an optimal biocatalyst for trehalose ester production.
• The novel compound has been purified and identified as 6-o-trehalose lipoate.
• The antioxidant activity of purified ester was 2.5-fold higher than lipoic acid.
• Stepwise addition combine co-solvent system improved 20% trehalose ester yield.

In the present work, we attempted to produce novel trehalose ester derivatives catalyzed by lipase using trehalose and lipoic acid as substrates. Our aim was to select the lipase with the highest catalytic efficiency as a biocatalyst to efficiently produce trehalose ester derivatives with the lowest production cost for further industrial applications. The highest conversion yields of trehalose lipoate (75.9 ± 1.9%) were obtained at the following optimal conditions: reaction temperature 40 °C, reaction time 4 days, substrate molar ratio 1:4 (trehalose:lipoic acid), total enzyme activity 3000 PLU (propyl laurate units), four stepwise additions of lipoic acid (0.03 mmol/day) and a cosolvent ratio of 4:1 [DMSO:2-methyl-2-butanol(2M2B)]. After isolation and purification, the carboxyl group of lipoic acid was determined to be connected to the C6 hydroxyl group of trehalose using nuclear magnetic resonance. The DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging activity (%) of purified 6-o-trehalose lipoate was at least 2.5-fold higher than that of lipoic acid. This bioactive trehalose ester exhibits improved antioxidant activity, which may have higher health benefits than those of lipoic acid, in various functional product applications.