Abstract
In order to improve the capability of Klebsiella pneumoniae to produce an important chemical raw material, 1,3-propanediol (1,3-PDO), a new type of K. pneumoniae x546 was obtained by glycerol acclimation and subsequently was used to produce 1,3-PDO. Under the control of pH value using Na+ pH neutralizer, the 1,3-PDO yield of K. pneumoniae x546 in a 7.5-L fermenter was 69.35 g/L, which was 1.5-fold higher than the original strain (45.91 g/L). After the addition of betaine, the yield of 1,3-PDO reached up to 74.44 g/L at 24 h, which was 40% shorter than the original fermentation time of 40 h. To study the potential mechanism of the production improvement of 1,3-PDO, the Tandem Mass Tags (TMT) technology was applied to investigate the production of 1,3-PDO in K. pneumoniae. Compared with the control group, 170 up-regulated proteins and 291 down-regulated proteins were identified. Through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis, it was found that some proteins [such as homoserine kinase (ThrB), phosphoribosylglycinamide formyltransferase (PurT), phosphoribosylaminoimidazolesuccinocarboxamide synthase (PurC), etc.] were involved in the fermentation process, whereas some other proteins (such as ProX, ProW, ProV, etc.) played a significant role after the addition of betaine. Moreover, combined with the metabolic network of K. pneumoniae during 1,3-PDO, the proteins in the biosynthesis of 1,3-PDO [such as DhaD, DhaK, lactate dehydrogenase (LDH), BudC, etc.] were analyzed. The process of 1,3-PDO production in K. pneumoniae was explained from the perspective of proteome for the first time, which provided a theoretical basis for genetic engineering modification to improve the yield of 1,3-PDO. Because of the use of Na+ pH neutralizer in the fermentation, the subsequent environmental pollution treatment cost was greatly reduced, showing high potential for industry application in the future.
Highlights
IntroductionThe rise of the biodiesel industry leads to the overproduction of glycerol as a by-product, which threatens the economic feasibility of the industry (Pan et al, 2019; Kim et al, 2020)
Na2CO3 was used as the pH neutralizer in fermentation, and betaine was added to alleviate the high osmotic pressure caused by excessive Na+, which would significantly enhance the yield of 1,3-PDO
During the whole fermentation process, Na2CO3 was used as the pH neutralizer, which had an effect on the osmotic pressure of the fermentation liquid and the production yield of 1,3-PDO, so betaine as a fermentation medium was added (Fan et al, 2018)
Summary
The rise of the biodiesel industry leads to the overproduction of glycerol as a by-product, which threatens the economic feasibility of the industry (Pan et al, 2019; Kim et al, 2020) This situation has prompted scientists to explore the utilization of glycerol as a carbon source to produce 1,3-propanediol (1,3PDO), which is a precursor of some important commercial polymers such as polyester and polyurethane (Zhou et al, 2019b; Bao et al, 2020; Chen et al, 2020). The Tandem Mass Tags (TMT) technology was one of the most powerful analytical methods with the highest flux, the smallest systematic error, and the most powerful function (Sogame et al, 2014) It could provide more accurate digital signals, higher detection fluxes, and wider detection ranges. It is necessary to apply the TMT technology to the study of 1,3-PDO production by K. pneumoniae
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