Sustainable biosynthetic pathways to value-added bioproducts from hydroxycinnamic acids.

The biorefinery concept, in which biomass is utilized for the production of fuels and chemicals, emerges as an eco-friendly, cost-effective, and renewable alternative to petrochemical-based production. The hydroxycinnamic acid fraction of lignocellulosic biomass represents an untapped source of aromatic molecules that can be converted to numerous high-value products with industrial applications, including in the flavor and fragrance sector and pharmaceuticals. This review describes several biochemical pathways useful in the development of a biorefinery concept based on the biocatalytic conversion of the hydroxycinnamic acids ferulic, caffeic, and p-coumaric acid into high-value molecules. KEY POINTS: • The phenylpropanoids bioconversion pathways in the context of biorefineries • Description of pathways from hydroxycinnamic acids to high-value compounds • Metabolic engineering and synthetic biology advance hydroxycinnamic acid-based biorefineries.

Identification of a New Endo-ß-1,4-xylanase Prospected from the Microbiota of the Termite Heterotermes tenuis.

Xylanases are hemicellulases that break down xylan to soluble pentoses. They are used for industrial purposes, such as paper whitening, beverage clarification, and biofuel production. The second-generation bioethanol production is hindered by the enzymatic hydrolysis step of the lignocellulosic biomass, due to the complex arrangement established among its constituents. Xylanases can potentially increase the production yield by improving the action of the cellulolytic enzyme complex. We prospected endo-ß-1,4-xylanases from meta-transcriptomes of the termite Heterotermes tenuis. In silico structural characterization and functional analysis of an endo-ß-1,4-xylanase from a symbiotic protist of H. tenuis indicate two active sites and a substrate-binding groove needed for the catalytic activity. No N-glycosylation sites were found. This endo-ß-1,4-xylanase was recombinantly expressed in Pichia pastoris and Escherichia coli cells, presenting a molecular mass of approximately 20 kDa. Enzymatic activity assay using recombinant endo-ß-1,4-xylanase was also performed on 1% xylan agar stained with Congo red at 30 °C and 40 °C. The enzyme expressed in both systems was able to hydrolyze the substrate xylan, becoming a promising candidate for further analysis aiming to determine its potential for application in industrial xylan degradation processes.