p-Hydroxycinnamic acids (i. e., p-coumaric, ferulic, sinapic, and caffeic acids) are phenolic compounds involved in the biosynthesis pathway of lignin. These naturally occurring molecules not only exhibit numerous attractive properties, such as antioxidant, anti-UV, and anticancer activities, but they also have been used as building blocks for the synthesis of tailored monomers and functional additives for the food/feed, cosmetic, and plastics sectors. Despite their numerous high value-added applications, the sourcing of p-hydroxycinnamic acids is not ensured at the industrial scale except for ferulic acid, and their production cost remains too high for commodity applications. These compounds can be either chemically synthesized or extracted from lignocellulosic biomass, and recently their production through bioconversion emerged. Herein the different strategies described in the literature to produce these valuable molecules are discussed.

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This work reports on a solvent selection for the liquid-liquid extraction of p-coumaric acid produced by an engineered strain of Saccharomyces cerevisiae. The solvent selection is a key point of liquid-liquid extraction processes and this work describes a simple strategy to choose a suitable solvent for an in situ or in stream product recovery (ISPR) process during bioconversion. ISPR processes allow to limit the inhibition caused by end-products accumulation in the fermentation medium. The strategy consists in scoring different solvents based on different criteria weighted according to their significance for the process. Extraction performance, solvent biocompatibility and compatibility with materials, were chosen as essential criteria and the first two were assessed experimentally using distribution coefficients and flow cytometry, respectively. Following this first step, three solvents were selected as candidates for the process of interest and ranked according to the process needs using secondary criteria, namely safety, sourcing and price. Finally, oleyl alcohol obtained the highest score and was therefore considered as the most suitable candidate for an ISPR process with the aim of continuously extracting p-coumaric acid from the fermentation medium.This work is a first step towards the implementation of integrated extractive bioconversion for the production of bio-based molecules such as p-hydroxycinnamic acids and derivatives.

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Although organic UV-filters are extensively used in cosmetics to protect consumers from the deleterious effects of solar UV radiation-exposure, they suffer from some major drawbacks such as their fossil origin and their toxicity to both humans and the environment. Thus, finding sustainable and non-toxic UV-filters is becoming a topic of great interest for the cosmetic industry. A few years ago, sinapoyl malate was shown to be a powerful naturally occurring UV-filter. Building on these findings, we decided to design and optimize an entire value chain that goes from biomass to innovative biobased and non-toxic lignin-derived UV-filters. This multidisciplinary approach relies on: 1) The production of phenolic synthons using either metabolite extraction from biomass or their bioproduction through synthetic biology/fermentation/in stream product recovery; 2) their functionalization using green chemistry to access sinapoyl malate and analogues; 3) the study of their UV-filtering activity, their photostability, their biological properties; and 4) their photodynamics. This mini-review aims at demonstrating that combining biotechnology, green chemistry, downstream process and photochemistry is a powerful approach to transform biomass and, in particular lignins, into high value-added innovative UV-filters.