Production of anthocyanins in metabolically engineered microorganisms:Current status and perspectives

Microbial production of plant-derived natural products by engineered microorganisms has achieved great success thanks to large extend to metabolic engineering and synthetic biology.Anthocyanins,the water-soluble colored pigments found in terrestrial plants that are responsible for the red,blue and purple coloration of many flowers and fruits,are extensively used in food and cosmetics industry;however,their current supply heavily relies on complex extraction from plant-based materials.A promising alternative is their sustainable production in metabolically engineered microbes.Here,we review the recent progress on anthocyanin biosynthesis in engineered bacteria,with a special focus on the systematic engineering modifications such as selection and engineering of biosynthetic enzymes,engineering of transportation,regulation of UDP-glucose supply,as well as process optimization.These promising engineering strategies will facilitate successful microbial production of anthocyanins in industry in the near future.

Parallel screening and cheminformatics modeling of flavonoid activated aptasensors

A parallel screening of 27 different flavonoids and chalcones was conducted using 6 artificial naringenin-activated riboswitches(M1,M2,M3,O,L and H).A quantitative structure-property relationship approach was applied to understand the physicochemical properties of the flavonoid structures resulting in specificity differences relied on the fluorescence intensity of a green fluorescent protein reporter.Robust models of riboswitches M1,M2 and O that had good predictive power were constructed with descriptors selected for their high correlation.Increased electronegativity and hydrophilicity of the flavonoids structures were identified as two properties that increased binding affinity to RNA riboswitches.Hydroxyl groups at the C-3′and C-4’positions of the flavonoid molecule were strictly required for ligand-activation with riboswitches M1 and M2.Riboswitches O and L preferred multi-hydroxylated flavones as ligands.Substitutions on the A ring of the flavonoid molecule were not important in the molecular recognition process.O-glycosylated derivatives were not recognized by any of the riboswitches,presumably due to steric hindrances.Despite the challenges of detecting RNA conformational change after ligand binding,the resulting models elucidate important physicochemical features in the ligands for conformational structural studies of artificial aptamer complexes and for design of ligands having higher binding specificity.