Metabolic and process engineering for microbial production of protocatechuate with <i>Corynebacterium glutamicum</i>
Mohamed E. Labib, Jonas Görtz, Christian Brüsseler, Nicolai Kallscheuer, Jochem Gätgens, Andreas Jupke, Jan Marienhagen, Stephan Noack
Abstract
Abstract 3,4‐Dihydroxybenzoate (protocatechuate, PCA) is a phenolic compound naturally found in edible vegetables and medicinal herbs. PCA is of high interest in the chemical industry and has wide potential for pharmaceutical applications. We designed and constructed a novel Corynebacterium glutamicum strain to enable the efficient utilization of d ‐xylose for microbial production of PCA. Shake flask cultivation of the engineered strain showed a maximum PCA titer of 62.1 ± 12.1 mM (9.6 ± 1.9 g L −1 ) from d ‐xylose as the primary carbon and energy source. The corresponding yield was 0.33 C‐mol PCA per C‐mol d ‐xylose, which corresponds to 38% of the maximum theoretical yield. Under growth‐decoupled bioreactor conditions, a comparable PCA titer and a total amount of 16.5 ± 1.1 g PCA could be achieved when d ‐glucose and d ‐xylose were combined as orthogonal carbon substrates for biocatalyst provision and product synthesis, respectively. Downstream processing of PCA was realized via electrochemically induced crystallization by taking advantage of the pH‐dependent properties of PCA. This resulted in a maximum final purity of 95.4%. The established PCA production process represents a highly sustainable approach, which will serve as a blueprint for the bio‐based production of other hydroxybenzoic acids from alternative sugar feedstocks.