Pretreatment strategies for microbial valorization of bio-oil fractions produced by fast pyrolysis of ash-rich lignocellulosic biomass

This work evaluates a biorefinery approach for microbial valorization of bio-oil fractions produced by fast pyrolysis of ash-rich lignocellulosic biomass. Different methods are presented for the pretreatment of the low-sugar complex bio-oil consisting of organic condensate (OC) and aqueous condensate (AC) to overcome their strong inhibitory effects and unsuitability for common analytical methods. Growth of Pseudomonas putida KT2440, which was chosen as a reference system, on untreated bio-oil fractions was only detectable using solid medium with OC as sole carbon source. Utilization of a pretreated OC which was filtered, autoclaved, neutralized and centrifuged enabled growth in liquid medium with significant remaining optical instability. By subjecting the pretreated fractions to solid phase extraction, more stable and less inhibitory bio-oil fractions could be obtained enabling the appliance of common analytical methods. Furthermore, this pretreatment facilitated growth of the applied reference organism Pseudomonas putida KT2440. As there is currently no convincing strategy for reliable application of bio-oil as a sole source of carbon in industrial biotechnology, the presented work depicts a first step toward establishing bio-oil as a future sustainable feedstock for a bio-based economy.