Acetate accumulation through alternative metabolic pathways in ackA − pta − poxB − triple mutant in E. coli B (BL21)

Abstract

Individual deletions of acs and aceA genes in E. coli B (BL21) showed little difference in the metabolite accumulation patterns but deletion of the ackA gene alone or together with pta showed acetic acid gradually accumulated to 3.1 and 1.7 g/l, respectively, with a minimal extended lag in bacterial growth and a higher pyruvate formation. Single poxB deletion in E. coli B (BL21) or additional poxB deletion in the ackA-pta mutants did not change the acetate accumulation pattern. When the acetate production genes (ackA-pta-poxB) were deleted in E. coli B (BL21) acetate still accumulated. This may be an indication that perhaps acetate is not only a by-product of carbon metabolism; it is possible that acetate plays also a role in other cellular metabolite pathways. It is likely that there are alternative acetate production pathways.

Engineering Escherichia coli BL21(DE3) Derivative Strains To Minimize E. coli Protein Contamination after Purification by Immobilized Metal Affinity Chromatography

“…On the other hand, we designed our acetate dependency assay based on data collected from experiments performed with E. coli K-12, since the two available control aceE mutants are K-12 strains (21). K-12 and B strains are known to contain major differences in their respective metabolic pathways, particularly in pyruvate and acetate production (33,34). For example, in high-density cultures, E. coli K-12 excretes high levels of acetate in the presence of excess glucose concentrations, which affects its growth rate, while E. coli BL21 is much less sensitive to glucose concentration and produces lower levels of acetate (32).…”

“…For example, in high-density cultures, E. coli K-12 excretes high levels of acetate in the presence of excess glucose concentrations, which affects its growth rate, while E. coli BL21 is much less sensitive to glucose concentration and produces lower levels of acetate (32). It seems that not only are the lower levels of production of pyruvate and acetate in E. coli BL21 the result of more-active carbon metabolism (TCA cycle, glyconeogenesis, glyoxylate shunt, and anaplerotic pathways), but glucose transport may be better controlled in BL21 than in K-12 (30,33). In conclusion, the acetate assay indicates that AceE-CBD is most likely active.…”

Reconstitution of TCA cycle with DAOCS to engineer Escherichia coli into an efficient whole cell catalyst of penicillin G

“…Taking the carbon balance in the system into consideration, decrease in acetate production will not only prevent acidification of the reaction medium but also reduce the carbon loss from the system, which may increase the availability of acetyl-CoA to drive the G-7-ADCA production. There are two major acetate-producing pathways in aerobically grown E. coli: the PoxB and phosphotransacetylase-acetate kinase (Pta-AckA) pathways (19,20). Elimination of the Pta-AckA (△pta△ackA) pathway is an effective method to reduce acetate formation (19,20).…”

“…There are two major acetate-producing pathways in aerobically grown E. coli: the PoxB and phosphotransacetylase-acetate kinase (Pta-AckA) pathways (19,20). Elimination of the Pta-AckA (△pta△ackA) pathway is an effective method to reduce acetate formation (19,20). However, the deletion of ackA or pta also impaired growth (19,20).…”

Alternative Acetate Production Pathways inChlamydomonas reinhardtiiduring Dark Anoxia and the Dominant Role of Chloroplasts in Fermentative Acetate Production

“…In Corynebacterium glutamicum, all acetate biosynthesis in anoxic cultures is a consequence of the production of acetylCoA by pyruvate dehydrogenase (Blombach et al, 2007;Yasuda et al, 2007). In other organisms, acetate can be generated by the oxidative catabolism of pyruvate to acetate and CO 2 by pyruvate quinone oxidoreductase and pyruvate oxidoreductase (Lin et al, 2003;Lorquet et al, 2004;Schreiner et al, 2006;Phue et al, 2010).…”