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

• Published in: Biotechnology and bioengineering 2020-05, Vol.117 (5), p.1381-1393
• Main Authors: Duuren, Jozef B. J. H., Wild, Paul J., Starck, Sören, Bradtmöller, Christian, Selzer, Mirjam, Mehlmann, Kerstin, Schneider, Roland, Kohlstedt, Michael, Poblete‐Castro, Ignacio, Stolzenberger, Jessica, Barton, Nadja, Fritz, Michel, Scholl, Stephan, Venus, Joachim, Wittmann, Christoph
• Format: Article
• Language: English
• Subjects: Acids; Adipic acid; Aromatic compounds; Benzoates; Biocatalysts; Bioconversion; Bioreactors; Carbon dioxide; Carbon sources; Catechol; cis; cis‐muconic acid; Cost analysis; Cresols; Distillation; Empirical analysis; Energy demand; fast‐pyrolysis; Fermentation; Gases; Guaiacol; Life cycle analysis; Life cycle assessment; Life cycles; Lignin; Microorganisms; Muconic acid; Petrochemicals industry; Phenols; Pseudomonas putida; Pseudomonas putida KT2440; Pyrolysis; Softwoods; Steam; Substrates
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.27299

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. A fast‐pyrolysis process using softwood lignin resulting in a two‐phase bio‐oil was applied. Van Duuren and co‐workers have shown that 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. Based on a limited life cycle and cost analysis of an integrated biotechnological and chemical process for producing adipic acid, the authors have estimated its environmental benefits and cost‐effectiveness.