Production of d-Xylonate from Corn Cob Hydrolysate by a Metabolically Engineered Escherichia coli Strain

Abstract

Corn cob is the secondary agricultural residue that can be easily hydrolyzed into hydrolysate with abundant d-xylose. Besides d-xylose, d-glucose, and l-arabinose are also utilizable sugars in corn cob hydrolysate. Here, we established a coutilization system through which recombinant Escherichia coli can use d-glucose and l-arabinose supporting its growth and convert d-xylose in corn cob hydrolysate into d-xylonate. First, biosynthetic pathway of d-xylonate was overexpressed and two xylonate dehydratases were knocked out in E. coli W3110 to enhance d-xylonate production from d-xylose. Then, the genes responsible for acetate, ethanol, and lactate synthesis were knocked out to decrease these byproducts production during the growth of the recombinant strain. Three successive strategies were employed to enhance the d-xylonate productionusing lactose as the inducer, eliminating carbon catabolite repression, and inactivating the lactose degradation. Finally, 108.2 g/L d-xylonate was produced with a yield of 1.09 g of d-xylonate/g of d-xylose using d-xylose as the substrate and d-glucose as the carbon source through fed-batch fermentation. When corn cob hydrolysate was used, 91.2 g/L d-xylonate was produced with a specific productivity of 1.52 g/[L·h]. This study is valuable not only for producing d-xylonate but also for providing a coutilization system to obtain other important chemicals from corn cob hydrolysate.

Efficient 2,3-butanediol production from whey powder using metabolically engineered Klebsiella oxytoca

“…The optical density (OD) was measured at 600 nm using a spectrophotometer (V5100H, Shanghai Metash Instruments Co., Ltd, China) after an appropriate dilution. The concentrations of lactose and other by-products were detected by high performance liquid chromatography (HPLC) in an Agilent 1100 series, equipped with a Aminex HPX-87H column (300 × 7.8 mm; Bio-Rad, USA) and a refractive index detector [40]. The mobile phase was 10 mM H 2 SO 4 at a flow rate of 0.4 mL/min at 55 °C.…”

“…Luria-Bertani (LB) medium was used for the cultivation of all the strains used. The M9 minimal medium [40] supplemented with 5 g/L yeast extract and 40 g/L lactose was used in shake flasks experiments for selection of the efficient BDO producing strain. The selection medium for single exchange strains of K. oxytoca was M9 minimal medium supplemented with 20 g/L sodium citrate and 40 µg/mL chloramphenicol.…”

Efficient 2,3-butanediol production from whey powder using metabolically engineered Klebsiella oxytoca

“…Luria-Bertani (LB) medium was used for the cultivation of all the strains used. The M9 minimal medium [40] supplemented with 5 g/L yeast extract and 40 g/L lactose was used in shake asks experiments for selection of the e cient BDO producing strain. The selection medium for single exchange strains of K. oxytoca was M9 minimal medium supplemented with 20 g/L sodium citrate and 40 µg/mL chloramphenicol.…”

“…The optical density (OD) was measured at 600 nm using a spectrophotometer (V5100H, Shanghai Metash Instruments Co., Ltd, China) after an appropriate dilution. The concentrations of lactose and other by-products were detected by high performance liquid chromatography (HPLC) in an Agilent 1100 series, equipped with a Aminex HPX-87H column (300×7.8 mm; Bio-Rad, USA) and a refractive index detector [40]. The mobile phase was 10 mM H 2 SO 4 at a ow rate of 0.4 mL/min at 55 °C.…”

Simple and Practical Multigram Synthesis of d-Xylonate Using a Recombinant Xylose Dehydrogenase

“…As this enzyme is more efficient for d -xylose oxidation, the production of d -xylonate was greatly improved in the organisms modified with this gene. 18−21 Further improvements of d -xylonate production have been accomplished by addition of the lactonase XylC also from C. crescentus . 22,23…”