Scientist - Anaerobic Strain Engineering

Full-time, $80,000 - $120,000 depending on experience and domain expertise, Stock options, Medical, dental, vision

Purpose Bio is an early-stage biotech spun out of the Hsiao Lab  are building an oral, non-hormonal, non-systemic platform of engineered enzymes that act on the gut-liver axis across MASLD/MASH, obesity, and PSC.

We are small, fast, and unusually well-advised, with a scientific advisory board that includes leaders in microbiome and metabolic disease.

Our purpose is to treat the root cause of metabolic disease rather than its symptoms, and to bring a safer option to a patient population that has largely been left without one.

This role carries genuine ownership of the platform's scientific direction. We are looking for a scientist with the experience and judgment to make consequential decisions independently, and the creativity to shape how the platform is built rather than execute a predetermined approach.

You will own strain engineering end to end, from construct design through a functional live biotherapeutic candidate. Our near-term work centers on characterizing native enzyme candidates in our strains. As the platform advances, engineering those enzymes becomes the next phase, and a scientist who can lead that as well would have the opportunity to own it.

What you will do:

• Design, build, and characterize engineered anaerobic bacterial strains, including plasmid systems, genome integration, knockouts, and expression tuning.
• Screen and characterize native enzyme candidates for activity and expression in our strains, and build the assays that tell us which ones are worth carrying forward
• Build the assay infrastructure that tells us whether a construct is actually working, and iterate fast on what it tells you
• Partner with our in vivo team to move candidates from bench into mouse models, and interpret what comes back
• Contribute directly to IP strategy and grant applications, and grow into CMC and IND-enabling work as the company does

• PhD in microbiology, molecular biology, biochemistry, chemical biology, bioengineering, or a closely related field
• Demonstrated anaerobic strain engineering experience. You have built genetic tools for obligate anaerobes.
• A track record you can point to. First-author publications, a thesis, postdoc, or industry project you drove, or tools you built that other people now use
• Based in Los Angeles or willing to relocate. This role is on-site, and we are looking to fill it quickly.
• Authorized to work in the United States

• Protein and enzyme engineering depth. Rational or computational protein design, directed evolution, structure-function analysis, enzyme kinetics. Someone who thinks in terms of active sites and catalytic residues, not just constructs. Candidates with strength in both this and anaerobic strain engineering are of particular interest
• Experience contributing to IND-enabling work. CMC development, strain characterization and release testing, GLP-adjacent documentation, or any hands‑on role in moving a program toward an IND filing. Familiarity with the regulatory pathway for live biotherapeutic products is a significant advantage
• Knowledge of gut‑liver axis metabolic mechanisms
• Knowledge of host nuclear receptor and metabolite signaling in liver and metabolic disease
• Experience with live biotherapeutic products, or microbiome therapeutics
• LC-MS or metabolomics fluency
• Prior industry or startup exposure, including employment, internships, consulting, or industry collaborations during your PhD or postdoc

We are open to industry scientists, to PhDs entering industry directly, and to scientists making their first move out of academia. Prior industry experience is valuable and welcome, but it is not a requirement.

For candidates weighing this against a larger company, what this role offers that a large pharma position would not:

• Your name on the platform from the beginning, and equity that reflects it
• Project ownership and making big experimental decisions
• Direct exposure to IP prosecution, grant strategy, and regulatory planning, not just bench work
• Mentorship from senior industry advisors who have taken programs into the clinic

This environment suits scientists who value autonomy, creativity, speed and ownership. Candidates who work best within a defined support system should weigh that carefully.

• Creative and willing to take the lead and drive their project pipeline. You will be the expert and will need to feel comfortable making tough decisions
• Fast at the bench. Cycle time is our real currency at this stage
• Comfortable with a lean budget and knows how to strategically optimize experimentation
• A real team player. Small teams amplify whoever is in them, in both directions. We are protective of that and are only hiring great collaborative team members, so everyone is excited to come to the lab every day
• Bold. We are not optimizing an incremental asset

• Compensation: $80,000 - $120,000 base,…