Enzymatic Glycosylation of Anthranilates for Enhanced Functionality

Anthranilate (ANT) is a precursor for the synthesis of valuable compounds, including its alkyl esters (AEANTs), such as methyl anthranilate (MANT). These derivatives are industrial petrochemical products used as flavouring agents and bird repellents. Due to the mandatory green transition, their biological industrial production must be considered. However, their antimicrobial activity and physicochemical properties inhibit efficient microbial production and challenge their practical use. To overcome this, we explored enzymatic glycosylation using UDP-dependent glycosyltransferases (UGTs). Screening identified three UGTs with activity on a selected AEANT panel, with UGT72B68 from Solanum lycopersicum showing the highest efficiency (840 s-1 M-1) for MANT. Rational engineering produced a mutant (F145M) with improved activity for bulkier AEANTs. We scaled up enzymatic synthesis, producing 9.3 g of MANT-N-glucose (>99% purity, 74% yield). With this in hand, we observed that MANT-N-glucose has a significantly lower impact on the growth of E. coli and P. putida, supporting microbial production. Furthermore, we found that MANT-N-glucose completely inhibited sunflower seed consumption, compared to a 70% reduction observed in a previous study using MANT, when tested on captured red-winged blackbirds. Finally, a preliminary life-cycle assessment demonstrated that microbially produced MANT-N-glucose is a viable alternative to chemically synthesised MANT as a bird repellent.