Biocatalytic Oxidation of Biobased Furan Aldehydes: Comparison of Toxicity and Inhibition of Furans toward a Whole-Cell Biocatalyst

Abstract

Furan carboxylic acids are promising and renewable building blocks in polymer and pharmaceutical industries. In this work, biocatalytic synthesis of furan carboxylic acids was performed from biobased furan aldehydes using recombinant Escherichia coli expressing 3-succinoylsemialdehyde-pyridine dehydrogenase (SAPDH). Particularly, the inhibition and toxicity of furan aldehydes and their carboxylic acid derivatives toward this whole-cell biocatalyst were evaluated. It was found that this biocatalyst displayed the highest tolerance level (200 mM) toward 5-hydroxymethylfurfural (HMF) in the oxidation of furan aldehydes, lower toward 5-methoxymethylfurfural (MMF, 150 mM), and the lowest (75 mM) toward furfural. This may be explained by the less detrimental effects of high concentrations of HMF on the biocatalyst which might be closely related to the low hydrophobicity of this substance. In addition, the presence of furan carboxylic acids resulted in the substantial decrease in both catalytic activities and viability of the cells. The inhibition and toxicity of furan carboxylic acids toward the cells were greatly relieved upon neutralization with a base. Based on the results obtained above, a combined reaction engineering strategy (fed-batch operation coupled with pH controlling) was designed for efficient synthesis of 5-methoxymethyl-2-furancarboxylic acid (MMFCA) from MMF. In addition, the gram-scale preparation of MMFCA was implemented. The desired product was obtained in an isolated yield of 89% and a purity of >98%. Its space-time yield was up to 1.2 g/L h.

Engineering Promiscuous Alcohol Dehydrogenase Activity of a Reductive Aminase AspRedAm for Selective Reduction of Biobased Furans

“…Whole cells harboring variant N93A exhibited significantly different catalytic efficiencies toward furans 1 – 4 , although the activities of variant N93A toward these substrates were comparable (70–83 mU/mg, Table 4 ). For example, the reaction rate of furfural 2 was much higher than that of HMF 1 (times required for almost complete substrate conversion: 18 vs 6 h), which is in good agreement with our recent results ( Cheng et al, 2020 ). In addition to the activities of variant N93A, the transport rates of substrates across hydrophobic cell membranes might influence the reaction rates in whole-cell catalysis as well ( Almeida et al, 2007 ; Wierckx et al, 2011 ).…”

“…5-Methylfurfuryl alcohol (98%) was purchased from Apollo Scientific Ltd. (United Kingdom). 5-Methoxymethylfurfuryl alcohol was synthesized and purified according to a recent method ( Cheng et al, 2020 ). Other chemicals are of analytical grade and commercially available.…”

Selective Biosynthesis of Furoic Acid From Furfural by Pseudomonas Putida and Identification of Molybdate Transporter Involvement in Furfural Oxidation

“…A reasonable explanation was that the strategy developed in this study to enhance the catalytic performances of cells was valid and reliable, which was also evidenced by the difference between the crude activities of inducer-free cells and HMF-induced cells (Supplementary Figure 1). Compared to the microorganisms reported previously (Zhou et al, 2017;Shi et al, 2019;Cheng et al, 2020;Wang et al, 2020;Wen et al, 2020), biocatalysts of this study appeared to be much more prevailing in synthesis of FA from FAL, because of its high tolerance toward the substrate as well as good catalytic performances.…”

“…Of the recently reported strains, each one displayed a distinct tolerant profile. The oxidation of FAL by E. coli harboring SAPDH became very sluggish when FAL concentration was improved to 125 mM (Shi et al, 2019 ; Cheng et al, 2020 ), whereas the yield of FA sharply decreased to 32.1% using 75 mM FAL as initial substrate in the case of whole-cells of E. coli harboring HMFO variant (Wang et al, 2020 ). The substrate-adapted Comamonas testosteroni SC1588 cells could convert 50 mM FAL to the desired product with yield of 96% in 24 h, but only yield of 64% from 100 mM FAL even with the prolonged reaction time of 120 h (Wen et al, 2020 ).…”

Whole Cell Biocatalysis of 5-Hydroxymethylfurfural for Sustainable Biorefineries

“…An E. coli strain modified with 3-succinoylsemialdehyde-pyridine dehydrogenase (SAPDH) from C. testosteroni SC1588 was able to produce HMFCA from 50 mM HMF with 95% yield [57]. Later, this strain was found to maintain high HMFCA yields even from higher HMF concentrations: ~90% from 175 mM HMF and almost 80% from 200 mM HMF [58]. A vanillin dehydrogenase from C. testosteroni SC1588 was also introduced in an E. coli strain by the same research group, resulting in the conversion of 200 mM HMF with 92% yield, which was further improved by a fed-batch strategy resulting in the synthesis of 292 mM of HMFCA [59].…”