Abstract

  Lignocellulosic biomass deconstruction generates around 20 - 25 w/w% of hemicellulose derived xylose that must be exploited as a sugar platform for production of value-based chemicals. The absence of genes in the metabolic pathways for uptake and utilization of xylose in most microbes restricts its potential applicability to be used as carbon source. Rapidly evolving separation technologies dictate emerging preference for hetero-fermentation with high overall substrate based yields over lower yield homo-fermentations. Escherichia coli is known to metabolize both hexose and pentose sugars, and the present study describes construction and characterization of a double knock-out engineered mutant E. coli BW25113 ΔadhE ΔldhA for hetero-fermentative production of organic acids in > 90% yield on xylose majorly comprising of acetic acid. Fermentation parameters such as aeration, agitation, pH were observed to impact the xylose uptake rate, and consequently the acetate and total organic acid production rate. These investigative studies resulted in acetate yield and productivity of 0.51 ± 0.0027 g/g and 0.33 ± 0.0048 g/L.h; and a total organic acid yields and productivities of 0.92 ± 0.019 g/g and 0.61 ± 0.013 g/L.h on pure xylose. The modified strain demonstrated equivalent acetate yield of 0.51 ± 0.026 g/g and slightly reduced acetate productivity of 0.21 ± 0.011 g/L/h on lignocellulose derived xylose stream containing lignin, nitrate and furfural. Reduction in formate yield was possibly due to disproportion of formate to H₂ and CO₂ in the presence of nitrate in the lignocellulose derived xylose stream. Recovery of nitrate from the xylose fraction by employing a suitable filtration method can eliminate or reduce nitrate presence and provide higher formate yields. The study provides noteworthy insights on the practical applicability of lignocellulose derived xylose for commercial production of organic acids as important biochemical precursors.

Keywords: Escherichia coli; Lignocellulosic Biomass; Xylose; Organic Acids; Acetic Acid

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Citation

Citation: Arvind M Lali., et al. “Genetically Modified Escherichia coli for High Yield Mixed Organic Acid Production on Lignocellulosic Biomass Derived Xylose". Acta Scientific Biotechnology 1.9 (2020): 28-38.

Copyright

Copyright: © 2020 Arvind M Lali., et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.