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

Abstract

Propionic acid (PA) and its salts are widely used in the food, pharmaceutical, and chemical industries. Microbial production of PA by propionibacteria is a typical product-inhibited process, and acid resistance is crucial in the improvement of PA titers and productivity. We previously identified two key acid resistance elements-the arginine deaminase and glutamate decarboxylase systems-that protect propionibacteria against PA stress by maintaining intracellular pH homeostasis. In this study, we attempted to improve the acid resistance and PA production of Propionibacterium jensenii ATCC 4868 by engineering these elements. Specifically, five genes (arcA, arcC, gadB, gdh, and ybaS) encoding components of the arginine deaminase and glutamate decarboxylase systems were overexpressed in P. jensenii. The activities of the five enzymes in the engineered strains were 26.7-489.0% higher than those in wild-type P. jensenii. The growth rates of the engineered strains decreased, whereas specific PA production increased significantly compared with those of the wild-type strain. Among the overexpressed genes, gadB (encoding glutamate decarboxylase) increased PA resistance and yield most effectively; the PA resistance of P. jensenii-gadB was more than 10-fold higher than that of the wild-type strain, and the production titer, yield, and conversion ratio of PA reached 10.81 g/L, 5.92 g/g cells, and 0.56 g/g glycerol, representing increases of 22.0%, 23.8%, and 21.7%, respectively. We also investigated the effects of introducing these acid resistance elements on the transcript levels of related enzymes. The results showed that the expression of genes in the engineered pathways affected the expression of the other genes. Additionally, the intracellular pools of amino acids were altered as different genes were overexpressed, which may further contribute to the enhanced PA production. This study provides an effective strategy for improving PA production in propionibacteria; this strategy may be useful for the production of other organic acids. Biotechnol. Bioeng. 2016;113: 1294-1304. © 2015 Wiley Periodicals, Inc.

Comparative genomics and transcriptomics analysis‐guided metabolic engineering of Propionibacterium acidipropionici for improved propionic acid production

“…In the proteomic study, some of the identified proteins such as LysE and secretory protein were directly or indirectly involved in amino acid metabolism (Guan et al, ); the importance of amino acid metabolism in P. acidipropionici acid tolerance and PA production was apparent in the metabolomic analysis (Guan et al, ). The roles of arginine deaminase (ADI) and glutamate decarboxylase (GAD) systems on acid resistance in P. acidipropionici have been confirmed repeatedly in microenvironmental analyses (Guan et al, ) and metabolic engineering (Guan et al, ).…”

“…In our previous studies, the acid tolerance mechanism of P. acidipropionici was investigated at the levels of the microenvironment (Guan et al, ), proteins (Guan et al, ), and the metabolome (Guan et al, ). Additionally, acid‐resistance elements identified in these studies were engineered to improve the acid tolerance and PA production of P. jensenii (Guan et al, ). In this study, to further reveal the molecular mechanisms of acid tolerance and identify potential engineering targets, comparative genomic and transcriptomic analyses were conducted on wild‐type and acid‐tolerant P. acidipropionici .…”

Microbial Propionic Acid Production

“…[64] Genome editing, overexpression P. jensenii poxB or ldh knock-out and ppc overexpression Maximum 30% improvement in titre and 24% improvement productivity [65] Improve acid tolerance Overexpression P. acidipropionici otsA overexpression strain Propionic acid yield 11% higher. [66] Overexpression P. jensenii strains overexpressing gadB, arcA, arc, gdh or ybaS Up to a 1.5-fold increase in yield and 5.4-fold increase in titre, in shake flasks [67] Increase of metabolic flux towards propionate production Overexpression P. shermanii CoAT overexpression strain Increase yield and productivity, maximum 10% and 46%, respectively.…”

“…A novel approach for improving propionate production was explored by Guan et al by over-expressing acid resistance mechanisms in P. jensenii [67]. Compared to the strain harbouring an empty plasmid, over-expression of components of the arginine deiminase and glutamate decarboxylase systems typically improved the yield of propionate and the absolute titre reached in a glycerol media in shake-flasks.…”

Bio-produced Propionic Acid: A Review

“…Two key acid resistance elements, the arginine deaminase and glutamate decarboxylase systems, have been identified and modified to improve acid resistance by 10 fold and even propionic acid production by 20% with regard to Propionibacterium jensenii [31].…”