Limited life cycle and cost assessment for the bioconversion of lignin‐derived aromatics into adipic acid

Abstract

Lignin is an abundant and heterogeneous waste byproduct of the cellulosic industry, which has the potential of being transformed into valuable biochemicals via microbial fermentation. In this study, we applied a fast‐pyrolysis process using softwood lignin resulting in a two‐phase bio‐oil containing monomeric and oligomeric aromatics without syringol. We demonstrated that an additional hydrodeoxygenation step within the process leads to an enhanced thermochemical conversion of guaiacol into catechol and phenol. After steam bath distillation, Pseudomonas putida KT2440‐BN6 achieved a percent yield of cis, cis‐muconic acid of up to 95 mol% from catechol derived from the aqueous phase. We next established a downstream process for purifying cis, cis‐muconic acid (39.9 g/L) produced in a 42.5 L fermenter using glucose and benzoate as carbon substrates. On the basis of the obtained values for each unit operation of the empirical processes, we next performed a limited life cycle and cost analysis of an integrated biotechnological and chemical process for producing adipic acid and then compared it with the conventional petrochemical route. The simulated scenarios estimate that by attaining a mixture of catechol, phenol, cresol, and guaiacol (1:0.34:0.18:0, mol ratio), a titer of 62.5 (g/L) cis, cis‐muconic acid in the bioreactor, and a controlled cooling of pyrolysis gases to concentrate monomeric aromatics in the aqueous phase, the bio‐based route results in a reduction of CO2‐eq emission by 58% and energy demand by 23% with a contribution margin for the aqueous phase of up to 88.05 euro/ton. We conclude that the bio‐based production of adipic acid from softwood lignins brings environmental benefits over the petrochemical procedure and is cost‐effective at an industrial scale. Further research is essential to achieve the proposed cis, cis‐muconic acid yield from true lignin‐derived aromatics using whole‐cell biocatalysts.

Industrial biotechnology of Pseudomonas putida: advances and prospects

“…6 . A recent limited life cycle assessment concluded the feasibility of the bio-based production of adipic acid from softwood lignin-derived aromatics based on P. putida as the whole-cell biocatalyst (van Duuren et al 2020 ) and even possible offset credits were promoted for the bioethanol biorefinery, if the lignin in the their wastewater is no longer burnt but converted to the value-added product adipic acid instead (Corona et al 2018 ). Purification of MA produced by P. putida from lignin model compounds by activated carbon treatment was demonstrated with a good recovery at > 97% purity.…”

Mushroom Ligninolytic Enzymes―Features and Application of Potential Enzymes for Conversion of Lignin into Bio-Based Chemicals and Materials

“…Ideally, lignin conversion would reduce environmental impacts by saving energy in comparison with conventional petroleum-based products. Recently, an LCA for the production of lignin-derived adipic acid and catechol showed that it produces less CO 2 emissions and byproducts [166][167][168]. Most LCAs performed to data have concluded that lignin-based products offer better environmental performance than petroleum-based products due to their reduced impact in terms of climate change.…”

One-Pot Synthesis of Adipic Acid from Guaiacol in Escherichia coli

“…Valorization of lignin monomers directly into adipic acid is therefore an important challenge in chemical and synthetic biology. 2,6 Herein we report the synthesis of adipic acid from catechol (benzene-1,2-diol) and guaiacol (2-methoxyphenol) using engineered whole-cells of E. coli (Figure 1C). The one-pot reaction proceeds under mild conditions (37 ˚C, pH 7.2, aqueous media), requires no additives and produces no by-products.…”

“…To best of our knowledge, this is the first synthesis of adipic acid from guaiacol in an engineered microorganism. [5][6]18 Although the precise reason(s) for this latter increase in yield are currently unclear, the accumulation of ccMA and guaiacol in low-and high-OD reactions, respectively, indicates that a fine balance exists between GcoAB and BcER expression and activity in this pathway (Table S7).…”