Phenolics Value Chain and l-Lactic Acid Bioproduction from Agricultural Biomass

Abstract

To make the quantum leap from conceptualization of an idea to possible commercialization of a product, at first it would be desirable to have the opportunity to showcase the potential of a given product stream, successes, and the challenges involved. Using agricultural biomass as model feedstock, we feature in this chapter the tasks that were carried out in our laboratory in the context of bioproduction of vinyl phenols from two phenolic acids---vinyl guaiacol from ferulic acid and vinyl syringol from sinapic acid---as value-added chemicals. As a proof of concept, these monomers were polymerized to produce new biopolymers with improved properties. Along a similar product line, direct fermentation by a Rhizopus fungus of a nonfood feedstock to produce an optically pure l-lactic acid, a precursor to the well-known polyester, polylactic acid (PLA) was also featured. Technological advances made in these studies include the discovery and characterization of new enzymes viz. feruloyl esterases that release phenolic acids from lignocellulosic biomass. Guided by the 3-D structure of a phenolic acid decarboxylase (PAD), a novel sinapic acid decarboxylase (SAD) was evolved to effect the biotransformation of sinapic acid to vinyl syringol. Throughout the development, process optimization of various kinds was explored that include in situ recovery of water-insoluble compounds exemplified by vinyl guaiacol in a biphasic aqueous-solvent bioreactor system. We commented on some of the recent advances made in related areas and the necessity to push the green chemistry and innovation agenda forward for a sustainable future.