Fig. 3

Synthesis of VA from FA by R. palustris mediated whole-cell biocatalysis. a Schematic diagram of the biocatalytic route for VA synthesis from FA. FA: ferulic acid, FCoA: feruloyl-CoA, VA: vanillyl alcohol, VAC: vanillic acid. b The distribution profile of the products from 5 mM FA using different recombinant strains. Strains RVA1, RVA2, and RVA3 represent the base strain, the mutant with RPA1206 deletion, and the mutant with RPA1206, RPA1687 and RPA1725 deletions, respectively, containing CouBA-ADH2. c The effect of light exposure on the VA productions from different concentrations of FA incubating with the resting cells of RVA3 under dark- and light-anaerobic conditions. Two asterisk indicates statistically significant results (p < 0.005). d Time course of VA production from 30 mM FA by RVA3 using the pulse-feeding approach with supplementing 10 mM FA every 6 h under light-anaerobic conditions. The triangles represent for the feeding points. e Manipulation of carotenoid synthesis for reduced light shading. The absorption spectra and colour appearance of R. palustris under light-anaerobic conditions are provided. Strain YC3 (ispA^*), and YC4 (ispA^*crtE^*) represent the restriction of ispA and both ispA and crtE, respectively. f VA synthesis from 50 mM FA using strain RVA3 and RVA4 under the pulse-feeding mode by periodically adding 10 mM FA every 6 h. The triangles represent for the feeding points. All experiments were conducted in triplicate. Data represent the mean and standard deviations