One-Pot lignin bioconversion to polyhydroxyalkanoates based on hierarchical utilization of heterogeneous compounds.

Area of Science:

• Biotechnology
• Microbial Degradation
• Biorefining

Background:

• Lignin valorization is crucial for sustainable biorefining.
• Pseudomonas putida is a promising microorganism for degrading lignin compounds.
• Optimizing conditions for lignin degradation and valuable bioproducts like polyhydroxyalkanoates (PHA) remains a challenge.

Purpose of the Study:

• To investigate the effects of nitrogen availability and initial cell biomass on lignin degradation and PHA production by Pseudomonas putida.
• To elucidate the substrate utilization hierarchy of P. putida under different growth conditions.
• To develop an optimized one-pot strategy for lignin bioconversion and PHA production.

Main Methods:

• Cultivation of Pseudomonas putida with alkali-pretreated lignin liquor under varying nitrogen conditions.
• Optimization of initial cell biomass concentration for enhanced lignin degradation.
• Analysis of substrate utilization patterns and PHA production.
• Augmentation of acetate to facilitate one-pot bioconversion under nitrogen-limited conditions.

Main Results:

• Nitrogen-replete conditions favored lignin degradation (35%) but yielded low PHA (PHA/dry cell weight).
• Nitrogen limitation increased PHA content (43%) but reduced lignin degradation (22%).
• Increased initial biomass (0.1-1.5 g/L) under nitrogen limitation improved lignin degradation (22% to 33%).
• A hierarchical utilization of compounds was observed: simple carbon sources first, then aromatics.
• Augmenting acetate under nitrogen-limited conditions with optimized biomass improved lignin bioconversion (near 35%) and PHA yield (39 mg/g-lignin).
• Redesigned anaerobic digestion favored acetate production (91 wt%), providing an economic feedstock.

Conclusions:

• Nitrogen availability and initial biomass are critical factors in balancing lignin degradation and PHA production by P. putida.
• Acetate augmentation and optimized biomass enable efficient one-pot lignin bioconversion and PHA synthesis.
• This study presents a viable strategy for lignin valorization and sustainable production of PHA and acetate.