High performance thin layer chromatography determination of cellobiosan and levoglucosan in bio-oil obtained by fast pyrolysis of sawdust

Next Challenges for the Comprehensive Molecular Characterization of Complex Organic Mixtures in the Field of Sustainable Energy

The conversion of lignocellulosic biomass by pyrolysis or hydrothermal liquefaction gives access to a wide variety of molecules that can be used as fuel or as building blocks in the chemical industry. For such purposes, it is necessary to obtain their detailed chemical composition to adapt the conversion process, including the upgrading steps. Petroleomics has emerged as an integral approach to cover a missing link in the investigation bio-oils and linked products. It relies on ultra-high-resolution mass spectrometry to attempt to unravel the contribution of many compounds in complex samples by a non-targeted approach. The most recent developments in petroleomics partially alter the discriminating nature of the non-targeted analyses. However, a peak referring to one chemical formula possibly hides a forest of isomeric compounds, which may present a large chemical diversity concerning the nature of the chemical functions. This identification of chemical functions is essential in the context of the upgrading of bio-oils. The latest developments dedicated to this analytical challenge will be reviewed and discussed, particularly by integrating ion source features and incorporating new steps in the analytical workflow. The representativeness of the data obtained by the petroleomic approach is still an important issue.

Conversion of levoglucosan and cellobiosan by Pseudomonas putida KT2440

Pyrolysis offers a straightforward approach for the deconstruction of plant cell wall polymers into bio-oil. Recently, there has been substantial interest in bio-oil fractionation and subsequent use of biological approaches to selectively upgrade some of the resulting fractions. A fraction of particular interest for biological upgrading consists of polysaccharide-derived substrates including sugars and sugar dehydration products such as levoglucosan and cellobiosan, which are two of the most abundant pyrolysis products of cellulose. Levoglucosan can be converted to glucose-6-phosphate through the use of a levoglucosan kinase (LGK), but to date, the mechanism for cellobiosan utilization has not been demonstrated. Here, we engineer the microbe Pseudomonas putida KT2440 to use levoglucosan as a sole carbon and energy source through LGK integration. Moreover, we demonstrate that cellobiosan can be enzymatically converted to levoglucosan and glucose with β-glucosidase enzymes from both Glycoside Hydrolase Family 1 and Family 3. β-glucosidases are commonly used in both natural and industrial cellulase cocktails to convert cellobiose to glucose to relieve cellulase product inhibition and to facilitate microbial uptake of glucose. Using an exogenous β-glucosidase, we demonstrate that the engineered strain of P. putida can grow on levoglucosan up to 60 g/L and can also utilize cellobiosan. Overall, this study elucidates the biological pathway to co-utilize levoglucosan and cellobiosan, which will be a key transformation for the biological upgrading of pyrolysis-derived substrates.

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Levoglucosan kinase is engineered into Pseudomonas putida KT2440.

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Cellobiosan can be cleaved to levoglucosan and glucose by β-glucosidases.

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This provides a path forward to co-utilize levoglucosan and cellobiosan.

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These transformations will be important for hybrid processing applications.