Improved Production of Propionic Acid in Propionibacterium jensenii via Combinational Overexpression of Glycerol Dehydrogenase and Malate Dehydrogenase from Klebsiella pneumoniae

Abstract

dMicrobial production of propionic acid (PA), an important chemical building block used as a preservative and chemical intermediate, has gained increasing attention for its environmental friendliness over traditional petrochemical processes. In previous studies, we constructed a shuttle vector as a useful tool for engineering Propionibacterium jensenii, a potential candidate for efficient PA synthesis. In this study, we identified the key metabolites for PA synthesis in P. jensenii by examining the influence of metabolic intermediate addition on PA synthesis with glycerol as a carbon source under anaerobic conditions. We also further improved PA production via the overexpression of the identified corresponding enzymes, namely, glycerol dehydrogenase (GDH), malate dehydrogenase (MDH), and fumarate hydratase (FUM). Compared to those in wild-type P. jensenii, the activities of these enzymes in the engineered strains were 2.91-؎ 0.17-to 8.12-؎ 0.37-fold higher. The transcription levels of the corresponding enzymes in the engineered strains were 2.85-؎ 0.19-to 8.07-؎ 0.63-fold higher than those in the wild type. The coexpression of GDH and MDH increased the PA titer from 26.95 ؎ 1.21 g/liter in wild-type P. jensenii to 39.43 ؎ 1.90 g/liter in the engineered strains. This study identified the key metabolic nodes limiting PA overproduction in P. jensenii and further improved PA titers via the coexpression of GDH and MDH, making the engineered P. jensenii strain a potential industrial producer of PA.

Microbial Propionic Acid Production

“…It is difficult to extrapolate the potential implications of the failed acetate knock-out on glycerol [65] to the ability to use this strategy to overcome the yield challenges facing sugar fermentations. The over-expression of pathways that provide reduced cofactors, such as the pentose phosphate pathway, may be a more promising alternative as shown in our recent work [79], particularly since it may be impossible to eliminate acetate production by gene knock-out due to the promiscuity of the propionyl-CoA: succinate CoA-transferase (CoAT).…”

“…Necessarily, the strategies implemented to date have been relatively simple; in fact, the first study to co-express two genes in propionibacteria was published in 2015 [79]. Recently, genome-scale models for a number of closed Propionibacterium genomes [58] were developed and these were used to design rational engineering strategies in P. shermanii [34].…”

Bio-produced Propionic Acid: A Review

“…They usually form wet, bright and oily, round or granular colonies of a creamy, red, brown or orange colour. The genus of Propionibacteria is divided into two groups: dairy and cutaneous Propionibacteria [2]. Dairy Propionibacteria are widely used in the production of Swiss cheese, vitamin B12 and propionic acid.…”

“…Propionic acid titres have been improved by overexpressing enzymes such as glycerol dehydrogenase, malate dehydrogenase [2] and fumarate hydratase in Propionibacterium jensenii, phosphoenolpyruvate carboxylase (PPC) in Propionibacterium freudenreichii, and propionyl-CoA:succinate CoA transferase in Propionibacterium shermanii [8]. The yield of propionic acid was also increased by the inactivation of the acetate kinase gene [23].…”

Metabolic engineering of acid resistance elements to improve acid resistance and propionic acid production of Propionibacterium jensenii

“…shermanii (Wang et al, ). In a recent study, we constructed a Propionibacterium ‐ Escherichia coli shuttle vector for the metabolic engineering of Propionibacterium jensenii (Zhuge et al, ), and glycerol dehydrogenase and malate dehydrogenase genes have also been overexpressed to enhance PA production by P. jensenii (Liu et al, ).…”