Abstract
Production of 1,3-propanediol (1,3-PDO) from glycerol is a promising route toward glycerol biorefinery. However, the yield of 1,3-PDO is limited due to the requirement of NADH regeneration via glycerol oxidation process, which generates large amounts of undesired byproducts. Glutamate fermentation by Corynebacterium glutamicum is an important oxidation process generating excess NADH. In this study, we proposed a novel strategy to couple the process of 1,3-PDO synthesis with glutamate production for cofactor regeneration. With the optimization of 1,3-PDO synthesis route, C. glutamicum can efficiently convert glycerol into 1,3-PDO with the yield of ~ 1.0 mol/mol glycerol. Co-production of 1,3-PDO and glutamate was also achieved which increased the yield of glutamate by 18% as compared to the control. Since 1,3-PDO and glutamate can be easily separated in downstream process, this study provides a potential green route for coupled production of 1,3-PDO and glutamate to enhance the economic viability of biorefinery process.
Highlights
1,3-PDO with 3-hydroxypropionic acid (3-HP), an oxidation product of glycerol, for NADH recycling has been achieved in K. pneumoniae with an overall yield of 0.66 mol 1,3-PDO plus 3-HP per mol glycerol[19]
When cultured in LPG2 medium using glucose and glycerol as co-substrates, strain PT01 can grow and simultaneously utilize glucose and glycerol (Fig. 2). 16.2 g/L of 1,3-PDO was produced from 20.3 g/L of glycerol, with the yield of ~1.0 mol PDO/mol glycerol, suggesting that almost all of glycerol is converted into 1,3-PDO
With the introduction of 1,3-PDO synthesis pathway, the engineered C. glutamicum strains can convert almost all of glycerol into 1,3-PDO (~1.0 mol PDO/mol glycerol)
Summary
1,3-PDO with 3-hydroxypropionic acid (3-HP), an oxidation product of glycerol, for NADH recycling has been achieved in K. pneumoniae with an overall yield of 0.66 mol 1,3-PDO plus 3-HP per mol glycerol[19]. It was previously reported that disruption of oxidative phosphorylation via the deletion of H+-ATPase significantly enhanced glutamate production[30] Based on these observation, we propose a novel process to couple the production of 1,3-PDO with glutamate fermentation in C. glutamicum for efficient cofactor regeneration (Fig. 1). The produced glutamate and 1,3-PDO can be purified via classical separation processes such as crystallization and distillation (Fig. 1). This process may be integrated into current glutamate production line, increasing the economic viability of glutamate industry. We showed that co-production of glutamate and 1,3-PDO in one fermentation was possible and the yield of glutamate could be increased in the coupled process This is the first report of 1,3-PDO production by industrial important strain C. glutamicum
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