Escherichia coli KJ122 was engineered to produce succinate from glucose using the wild type GalP for glucose uptake instead of the native phosphotransferase system (ptsI mutation). This strain now ferments 10% xylose poorly. Mutants were selected by serial transfers in AM1 mineral salts medium with 10% xylose. Clones from this population all exhibited a similar improvement, co-fermentation of an equal mixture of xylose and glucose. One of these, AS1600a, produced 84.26 ± 1.37 g/L succinate, equivalent to that produced by the parent (KJ122) from 10% glucose (85.46 ± 1.78 g/L). AS1600a was sequenced and found to contain a mutation in galactose permease (GalP, G236D). This mutation was shown to be responsible for the improvement in fermentation using KJΔgalP as the host and expression vectors with native galP and with mutant galP(∗). Strain AS1600a and KJΔgalP(pLOI5746; galP(∗)) also co-fermented a mixture of glucose, xylose, arabinose, and galactose in sugarcane bagasse hydrolysate using mineral salts medium.

No abstract

A metabolically engineered Escherichia coli KJ122 was efficiently utilized for succinate production from cassava pulp during batch separate hydrolysis and fermentation (SHF) under simple anaerobic conditions. Succinate concentration of 41.46 ± 0.05 g/L with yield and productivity of 82.33 ± 0.14 g/100 g dry pulp and 0.84 ± 0.02 g/L/h was obtained. In batch simultaneous saccharification and fermentation (SSF), hydrolysis of 12 % (w/v) cassava pulp with an enzyme loading of 2 % AMG + 3 % Cel (v/w) at pH 6.5 was optimized at 39 °C. Succinate concentration of 80.86 ± 0.49 g/L with a yield of 70.34 ± 0.37 g/100 g dry pulp and a productivity of 0.84 ± 0.01 g/L/h was attained using E. coli KJ122. Fed-batch SSF significantly enhanced succinate concentration to 98.63 ± 0.12 g/L at yield and productivity of 71.64 ± 0.97 g/100 g dry pulp and 1.03 ± 0.01 g/L/h. This result indicated an efficient and economical succinate production from cassava pulp using SHF and SSF by the use of E. coli KJ122.

No abstract

BACKGROUND Succinate has been widely used in chemical industries and its microbial production is a desirable option. The feasibility of bio‐based succinate production on an industrial scale strongly depends on the utilization of cheaper renewable resources. The use of cassava starch may make the fermentation process of succinate more economically competitive. RESULTS Simultaneous saccharification and fermentation (SSF) of succinate production was performed in minimal salt medium containing a cheap cassava starch. The parameters affecting succinate production from cassava starch by E. coli KJ122 were optimized. A succinate concentration of 70.1 ± 0.1 g Ll−1 was produced with a yield of 1.00 ± 0.01 g g−1 substrate and productivity of 0.97 ± 0.01 g L−1h−1 during batch SSF in a 2 L fermentor under optimized conditions. Further improvements in succinate concentration (82.5 ± 0.7 g L−1), yield (1.03 ± 0.01 g g−1 glucose), and average and specific productivities of 1.15 ± 0.01 g L−1h−1, and 456 mg g CDW−1 h−1, respectively, were observed in fed‐batch SSF. CONCLUSION Escherichia coli KJ122 produced a succinate yield of 92% of theoretical maximum and the highest specific productivity ever reported. Succinate production yield and specific productivity from cassava starch in this study are superior to other previously published works. Escherichia coli KJ122 may be used as a biocatalyst for cost‐effective succinate production. © 2016 Society of Chemical Industry