Why does this project matter?

Lignocellulosic biomass (LCB) holds enormous promise as a renewable feedstock, but its inherent variability is a fundamental challenge for bioprocess design. The three main LCB components (cellulose, hemicellulose, lignin) vary substantially with plant species, geography, and season, and pre-treatment releases inhibitory compounds such as furfural, HMF, acetic acid and phenolics that impair microbial growth and productivity. No integrated Polyunsaturated fatty acid (PUFA) bioprocess has yet been systematically designed to accommodate this variability while maintaining high yields. P2 asks how fermentation processes can be engineered to be genuinely tolerant: both robust against inhibitors and flexible towards different feedstock sources.

What are we aiming to achieve?

P2 aims to develop a tolerant bioprocess for PUFA production using wild-type and engineered strains of R. opacus and S. cellulosum (in coordination with P1). Core objectives are: (1) characterize the effect of substrate composition and inhibitor load on microbial growth and PUFA yield; (2) define process windows in terms of substrate load, temperature, and feedstock composition; (3) design a biomass separation and PUFA extraction downstream process; and (4) generate quantitative process data for techno-economic and life cycle assessment in P9.

What will you work on as a PhD researcher?

As doctoral researcher in P2, you systematically investigate how different LCB feedstocks and their pre-treatment products affect microbial performance. You pre-treat four LCB sources  (corn stover, wheat straw, sugar beet pulp, beech wood) or obtain pretreated biomass from cooperation partners and characterize the hydrolysates by chemical analytics (HPLC). Growth of wild-type S. cellulosum and R. opacus on these substrates is investigated in microbioreactor systems (microtiter plates, parallel small-scale stirred bioreactors with online biomass monitoring), with systematic inhibition tests to build dose-response profiles for the most critical compounds.

Based on your results, you compare pre-treatment protocols for fermentation compatibility and evaluate detoxification options (activated charcoal, overliming) where needed. You also develop a PUFA extraction protocol in close collaboration with P7. All data – substrate compositions, growth curves, PUFA yields, inhibitor profiles – feed directly into the process simulation and LCA in P9 and guide strain engineering priorities in P1.

Skills and methods you will develop during your doctorate:

• Biomass pre-treatment and hydrolysate characterization

• Microbioreactor operation (microtiter plates, parallel small-scale bioreactors with online monitoring)

• Fermentation process development: growth kinetics, substrate and product analytics

• Lipid extraction

• Statistical design of experiments (DoE) for efficient parameter screening

• Process synthesis and data interpretation for bioprocess decision-making

• Cross-disciplinary collaboration with strain engineering (P1), separation process design (P7), and process modeling (P9)

Who will you work with and where?

The Lütz group has a strong track record in microbial and enzymatic process development, including whole-cell biocatalysis, fermentations with renewable feedstocks (xylose, lignocellulosic hydrolysates), and the production of high-value hydrophobic compounds such as limonene and monolignols. The laboratory is equipped with BioLector microtiter plate readers and parallel small-scale stirred bioreactors for high-throughput process development, lab-scale fermenters, HPLC and GC-MS analytics, and downstream processing equipment for biomass separation and product extraction. The group additionally has established infrastructure and expertise for techno-economic assessment and life cycle analysis of fermentation processes. Embedded in RTG TALENT, you gain access to a structured qualification program that combines advanced scientific training with transferable skills development, active exchange with academic and industrial collaboration partners, and tailored career support including the opportunity for a three-month placement in research, industry, or a start-up aligned with your career goals.