PHB production from cellobiose with Saccharomyces cerevisiae

Area of Science:

• Biotechnology
• Synthetic Biology
• Polymer Science

Background:

• Petrochemical-based materials pose environmental challenges.
• Microbial production of biodegradable polymers requires efficient fermentation processes.
• Lignocellulosic materials offer a sustainable feedstock but often require costly enzymes for sugar release.

Purpose of the Study:

• To demonstrate poly(hydroxybutyrate) (PHB) production in Saccharomyces cerevisiae using cellobiose as a sole carbon source.
• To evaluate two distinct cellobiose utilization pathways for PHB production.
• To enhance the economic viability of biodegradable polymer production.

Main Methods:

• Engineered Saccharomyces cerevisiae strains expressing PHB pathway genes and a cellodextrin transporter (CDT-1).
• Complementation with either β-glucosidase (GH1-1) or cellobiose phosphorylase (Cbp) for cellobiose breakdown.
• Cultivation in shake flasks and bioreactors under controlled conditions.

Main Results:

• Both GH1-1 and Cbp pathways enabled PHB production using cellobiose, outperforming glucose as a carbon source in terms of yield per sugar consumed.
• Strains with GH1-1 showed faster cellobiose consumption, while Cbp strains achieved higher PHB accumulation in shake flasks (10.0% vs 8.1% CDW).
• In bioreactors, GH1-1 strains achieved higher PHB accumulation (18.5% CDW) compared to Cbp strains (13.4% CDW), demonstrating improved performance under optimized conditions. High molecular weight PHB was produced via both routes.

Conclusions:

• Microbial production of PHB using cellobiose as a sole carbon source is feasible in engineered yeast.
• The choice between GH1-1 and Cbp pathways impacts fermentation dynamics and yield, with bioreactor conditions favoring the GH1-1 route for higher accumulation.
• Efficient cellobiose conversion and high molecular weight PHB production present a promising avenue for sustainable biopolymer manufacturing.