Promoting microbial utilization of phenolic substrates from bio-oil

Area of Science:

• Biotechnology
• Microbiology
• Chemical Engineering

Background:

• The economic feasibility of biorefineries hinges on effective lignin valorization.
• Biological upgrading using aromatic-catabolic microbes is a promising lignin valorization strategy.
• Fast pyrolysis and fractionation yield lignin monomers, but their low water solubility hinders microbial processing.

Purpose of the Study:

• To address the challenge of low water solubility for lignin-derived phenolic monomers.
• To investigate the use of an emulsifier blend to enhance the aqueous availability of phenolic monomers for microbial utilization.
• To evaluate the growth of *Pseudomonas putida* KT2440 with emulsified phenolic monomers.

Main Methods:

• An emulsifier blend of Tween® 20 (70 wt%) and Span® 80 (30 wt%) was formulated.
• Phenolic monomer-rich product from red oak fast pyrolysis was emulsified.
• Microbial growth of *Pseudomonas putida* KT2440 was assessed using optical density (OD600) measurements.

Main Results:

• *Pseudomonas putida* KT2440 achieved an optical density (OD600) of 1.0 ± 0.2 with 1.6 wt% emulsified phenolic monomers.
• The emulsifier dose was optimized at 0.076 ± 0.002 g emulsifier blend per g of phenolic monomer-rich product.
• The emulsification strategy partially mitigated the toxicity of p-coumarate but not benzoate or vanillin.

Conclusions:

• Emulsification of biomass-derived phenolics significantly enhances their aqueous availability.
• This approach represents a proof of concept for improving microbial utilization of lignin monomers.
• Further research is needed to address toxicity of specific phenolic compounds like benzoate and vanillin.