Project: Synthetic Biology for Sustainable Production of the Methionine Analongon HMTB

Acronym	SynBioMet (Reference Number: 20)
Duration	01/02/2021 - 01/01/2024
Project Topic	Due to growing concerns regarding the ongoing climate change, society and (therefore) industry are increasingly demanding for manufacturing processes that ensure a sustainable economic development. The product family of amino acids represents a particularly striking example for our growing technological ability to replace petrol-based syntheses of bulk chemicals by production processes that are based on the use of renewable resources. Out of the 20 proteinogenic amino acids that are industrially produced, 19 are currently synthesised by fermentation processes using renewable sugar as the primary carbon source. However, the essential amino acid methionine and its analogon 2-hydroxy-4-(methylthio)butyrate (HMTB), which are both primarily used as a supplement in animal feed and which have an annual production volume of more than 1.1 million tons, are still exclusively produced from the fossil resources petrol and natural gas. Economically viable fermentation processes are currently lacking for this amino acid, which is mainly due to the extremely high metabolic cost for sulphur incorporation that cause productivity and carbon yield to be insufficient compared to classical chemical synthesis. In this context, we have developed the concept of a two-stage process for the synthesis of the methionine analogon HMTB: in the first (fermentative) stage, the precursor molecule (L)-2,4-dihydrohybutyric acid (DHB) is produced by microorganisms using glucose as the feedstock. In the following (chemical) stage, conversion of DHB into α-hydroxy-γ-butyrolactone followed by incorporation of methanethiol directly gives rise to HMTB. The chemical incorporation of methanethiol bypasses the metabolically costly reduction of sulphur thereby enabling significantly higher carbon yields and productivities. The conversion of DHB into HMTB can be considered state-of-the-art chemistry which permits near to 100 % product yields. In contrast, the cost-effective production of DHB is an extremely challenging problem since chemical synthesis from γ-butyrolactone is feasible but too expensive, and because DHB is not a natural metabolite in life cells thus rendering classic metabolic engineering approaches unfeasible. To get access to DHB, we have recently developed three synthetic metabolic pathways which enable microbial synthesis of this compound starting from glucose (Figure 1). Several new-to-nature enzymatic activities have been engineered and implemented in producer strains to demonstrate feasibility of these metabolic routes. When these pathways were operated in non-optimized producer strains, DHB was produced from glucose at yields of 0.1 g/g through the homoserine and malyl-P-dependent pathways.
Network	ERA CoBioTech
Call	3rd Joint Call on Biotechnologies

Project partner

Number	Name	Role	Country
1	Technische Universität Dresden	Coordinator	Germany
2	Institute of Applied Sciences Toulouse	Partner	France
3	ESPCI	Partner	France
4	Adisseo	Partner	France