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

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.

Atomic force microscopy studies on the nanomechanical properties of Saccharomyces cerevisiae.

In the past years atomic force microscopy (AFM) techniques have turned out to be a suitable and versatile tool for probing the physical properties of microbial cell surfaces. Besides interaction forces, nanomechanical properties can be obtained from force spectroscopic measurements. Analyzing the recorded force curves by applying appropriate models allows the extraction of cell mechanical parameters, e.g. the Young's modulus or the cellular spring constant. In the present work the nanomechanical properties of the baker's yeast Saccharomyces cerevisiae are extensively studied by force spectroscopy using an AFM. Single cells deform purely elastically so that a cellular spring constant can reliably be determined. It is presented, how this spring constant depends on the probing position on the cell, and how it depends on the extracellular osmotic conditions. Investigations aiming a statistically firm description of the nanomechanical behavior of the yeast cell population are conducted. Finally, the informative value of the cellular spring constant as a cell mechanical parameter is critically discussed.