Development and Substrate Specificity Screening of an In Vivo Biosensor for the Detection of Biomass Derived Aromatic Chemical Building Blocks

Plant biomass is a sustainable, non-petrochemical based option to generate chemicals, materials, fuels and energy. Therefore, the degradation of lignocellulosic feedstocks, and release of chemical building blocks have high importance for industry and society in general. Lignin depolymerisation is a challenge for the adoption, optimisation and application of these alternative feedstocks and processes. Thus, there is a demand for new technologies enabling its degradation and valorization into high-value chemicals and biomaterials. Determination of substrate and/or product concentration in chemo-enzymatic and whole-cell biosynthetic processes can create a major bottleneck, as off-line biochemical activity methods and analytical methods (GC/LC-MS) are generally laborious. In this work, a whole cell biosensor that allows the intracellular detection of biomass-derived aromatic chemical building blocks was developed [1]. The biosensor was characterized and a specificity screening was performed. To demonstrate its utility in practical applications and against complex substrate mixtures, it was also used to screen the release of aromatic building blocks from different biomass/lignin sources enzymatically treated with a range of feruloyl esterases (EC 3.1.1.73, CAZy, CE1). Overall, the biosensor was able to detect 13 substituted cinnamic acid based compounds. The ferulic acid substrate was detected over a 13-fold sensitivity range, with >25-fold signal read-out range, and four other compounds displayed similar efficacy. Following enzyme treatment against wheat flour biomass, the biosensor screening confirmed the release of ferulic acid and/or closely related analogues. A similar relative activity profile was observed for the enzymes against micronized oat husk biomass, however with reduced signal. Thirdly, no activity was detected against kraft lignin biomass. The developed biosensor can be used to monitor the degradation of plant biomass and release of chemical building blocks. Therefore, enabling several applications, such as, the screening of lignin degrading strains/enzymes, the search of membrane transporters for lignin derived monomers/products and the production of high value chemicals including vanillin and flavonoids. This combination of applications will improve/expand the bioprocesses for lignocellulose valorization and support the chemical using industries to source chemical building blocks from alternative sustainable bio-based feedstocks.

[1] Machado LFM, Dixon N. Development and substrate specificity screening of an in vivo biosensor for the detection of biomass derived aromatic chemical building blocks. Chem Commun (Camb) 2016;52:11402–5. doi:10.1039/c6cc04559f.