Potential molecular targets in Clostridium spp. to obtain 1,3-propanediol from glycerol

• Grant number: 19/12044-9
• Support Opportunities: Scholarships abroad - Research
• Start date: October 23, 2019
• End date: December 22, 2019
• Field of knowledge: Biological Sciences - Microbiology - Applied Microbiology
• Principal Investigator: Valeria Reginatto Spiller
• Grantee: Valeria Reginatto Spiller
• Host Investigator: Hans-Peter Karl Heinrich Duerre
• Host Institution: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Institution abroad: Ulm University, Germany

Abstract

Several clostridium strains metabolize glycerol (C3) by two metabolic pathways: the reductive and the oxidative branches. In the reductive pathway, glycerol is dehydrated to 3-hydroxypropionaldehyde (3-HPA), which can be further reduced to 1,3-propanediol (1,3-PDO). The NADH cofactor of this reaction is generated by the oxidative glycerol pathway, thereby maintaining the intracellular redox balance, which might be critical for 1,3-PDO synthesis from glycerol. The generation of intracellular reducing power depends mainly on the carbohydrate oxidation. Deconstruction of lignocellulose-containing agricultural wastes releases fermentable monosaccharides such as glucose (C6) and xylose (C5). Many microorganisms can use C6 as a carbon source in industrial fermentations, but only a restricted number of microorganisms can consume C5. Fermentation of C3 alone and co-fermentation of C3 and C5 by clostridia will be used to regulate NADH supply, to increase 1,3-PDO production. The capacity of C. beijerinckii, C. pasteuranium, and C. butyricum to produce 1,3-PDO will be assayed by using pure glycerol and a combination of glycerol and xylose. The levels of gene expression in both carbon source conditions will be determined. The expression of dhaB1, dhaD1, dhaK, hydA, Pfo encoding the glycerol dehydratase (GDHt), glycerol dehydrogenase (GDH), dihydroxyacetone kinase (DHAK), hydrogenase (HYD), pyruvate-ferredoxin oxidoreductase (PFOR), which are key enzymes in glycerol metabolism in Clostridium, will be quantified and compared with some of the enzymatic activities. Clostridial cell samples will be collected during the fermentation assays. Then, mRNA extraction and cDNA synthesis will be done to perform qRT-PCR for selected genes. These actions will pave the way for future metabolic improvement of Clostridium strains for 1,3-PDO production. (AU)