Potential of biotechnological conversion of lignocellulose hydrolyzates by Pseudomonas putida KT2440 as a model organism for a bio-based economy

Lignocellulose-derived hydrolyzates typically display a high degree of variation depending on applied biomass source material as well as process conditions. Consequently, this typically results in variable composition such as different sugar concentrations as well as degree and the presence of inhibitors formed during hydrolysis. These key obstacles commonly limit its efficient use as a carbon source for biotechnological conversion. The gram-negative soil bacterium Pseudomonas putida KT2440 is a promising candidate for a future lignocellulose-based biotechnology process due to its robustness and versatile metabolism. Recently, P. putida KT2440_xylAB which was able to metabolize the hemicellulose (HC) sugars, xylose and arabinose, was developed and characterized. Building on this, the intent of the study was to evaluate different lignocellulose hydrolyzates as platform substrates for P. putida KT2440 as a model organism for a bio-based economy. Firstly, hydrolyzates of different origins were evaluated as potential carbon sources by cultivation experiments and determination of cell growth and sugar consumption. Secondly, the content of major toxic substances in cellulose and HC hydrolyzates was determined and their inhibitory effect on bacterial growth was characterized. Thirdly, fed-batch bioreactor cultivations with hydrolyzate as the carbon source were characterized and a diauxic-like growth behavior with regard to different sugars was revealed. In this context, a feeding strategy to overcome the diauxic-like growth behavior preventing accumulation of sugars is proposed and presented. Results obtained in this study represent a first step and proof-of-concept toward establishing lignocellulose hydrolyzates as platform substrates for a bio-based economy.