Smart Biotech Scientist | The CMC and Bioprocessing Podcast for Process Development and Manufacturing Leaders

Scale-up doesn't fail because the science was wrong. It fails because a cell's environment in a shake flask has little in common with its environment in a bioreactor. Christian Witz has spent years building the tools to close that gap: simulating exactly what a cell experiences as it moves from bench to plant, before a single liter is wasted finding out the hard way.
Continuing from Part 1, David Brühlmann and Christian Witz, CEO and founder of SimVantage, go deeper into how CFD moves from theory to daily practice: validating simulation results, scaling real cell therapy and Streptomyces processes, and an active FDA-backed project on residence time distribution in continuous bioprocessing.
Topics discussed:
Why data validation is crucial in CFD simulations and how to interpret and trust simulation results (02:39)
Real-world examples of scaling up from shake flasks to stirred tank reactors using CFD, including specific collaborations and cell therapy case studies (05:40)
Technical and validation challenges in simulating fluid dynamics in shake flasks and integrating these results into scale-up strategies (08:14)
Ongoing FDA-backed project to model residence time distribution in continuous bioprocessing and its regulatory significance (11:49)
The increasing openness of regulators like the FDA to include CFD data in submissions and relevant guidelines for simulation credibility (13:23)
Advice for small biotech teams on when and how to start using CFD in CMC development and scale-up planning (15:06)
Insights on the future of bioprocessing, including virtual scale-up, digital reactor repositories, and the democratization of CFD tools (18:20)
Smart insight: Christian Witz advised that teams begin CFD modeling as early as concept development. CFD not only helps choose the right equipment—even when working with contract manufacturers—but creates a digital process record that reduces experimental burden, shortens timelines, and impresses investors with its risk mitigation.
If this conversation got you rethinking your scale-up strategy, here are a few past episodes that go deeper on the pieces Christian touched on:
Episodes 91 - 92 : Mass Transfer Secrets: Mastering Bubbles and kLa from Bench to Large-Scale Production with Lars Puiman & Rik Volger
Episodes 245 - 246: Why Your Shake Flask Culture Doesn't Scale: OTR, Shaking Diameter, and How to Fix It with Tibor Anderlei
Episodes 173 - 174: Mastering Hybrid Model Digital Twins: From Lab Scale to Commercial Bioprocessing with Krist Gernaey
Episode 243: Turn Tech Transfer from a Gamble into a Managed Process: The 6-Pillar Biologics Scale-Up Framework
Connect with Christian Witz:
Website: www.simvantage.com
Christian’s LinkedIn: www.linkedin.com/in/christian-witz-84aa9b162/
Christian’s email: christian.witz@simvantage.com
Free 5-day email course, The CMC Failure Chain: the five recurring CMC mistakes that put your promising program at risk → Get it here
Support the show

You've perfected your process at the bench. Now comes the part that keeps CMC scientists up at night: will it still work at 2,000L? Right now, most teams find out the hard way, through failed runs, wasted batches, and months of delay to patients waiting on a therapy. Christian Witz believes there's a better way: use computational fluid dynamics to see how your cells will actually behave at full scale before you ever run the process, and stop treating scale-up as a guessing game.
On this episode of the Smart Biotech Scientist Podcast, David Brühlmann talks with Christian, founder of SimVantage, about why he treats CFD as a tool every process engineer should use directly, not something you outsource to a specialist. Christian's path into biotech ran through heat pump simulations and GPU-based particle flow modeling before he rebuilt a legacy Fortran bioreactor simulation program in modern C++ and CUDA, work that became the foundation of SimVantage.
Topics discussed:
Christian’s path from simulating heat pumps and particle flows to pioneering GPU-based bioreactor simulations (03:54)
The surprising lack of full equipment characterization in the biotech industry compared to fields like oil, gas, and iron & steel (06:40)
The interdisciplinary challenges and steep learning curve when entering biotech from other industries (08:07)
Why academic spinouts matter and the practical realities of founding a company based on university-developed software (09:44)
Reasons behind CFD’s low adoption in bioprocessing—perceived complexity, need for specialists, and historical limitations in algorithms and computing power (11:58)
How recent advances in GPU power, algorithms, and cloud computing remove barriers for routine use of CFD in process development (14:35)
Strategies for characterizing and scaling processes across various reactor types, from shake flasks to manufacturing reactors (16:39)
Practical considerations and limitations when setting up comprehensive CFD characterizations, including simulation parameter choices (19:49)
Smart insight: The degree of reactor characterization depends on a company’s needs. Startups might analyze a scale-up project once, while contract manufacturers—handling diverse products—benefit from comprehensive, reusable characterization across all reactors and operating conditions. Simulations are guided by physics (density, viscosity, surface tension) rather than biological specifics, allowing quick adaptation to new media or cell types.
If this conversation got you rethinking your scale-up strategy, here are a few past episodes that go deeper on the pieces Christian touched on:
Episodes 91 - 92 : Mass Transfer Secrets: Mastering Bubbles and kLa from Bench to Large-Scale Production with Lars Puiman & Rik Volger
Episodes 245 - 246: Why Your Shake Flask Culture Doesn't Scale: OTR, Shaking Diameter, and How to Fix It with Tibor Anderlei
Episodes 173 - 174: Mastering Hybrid Model Digital Twins: From Lab Scale to Commercial Bioprocessing with Krist Gernaey
Episode 243: Turn Tech Transfer from a Gamble into a Managed Process: The 6-Pillar Biologics Scale-Up Framework
Connect with Christian Witz:
Website: www.simvantage.com
Christian’s LinkedIn: www.linkedin.com/in/christian-witz-84aa9b162/
Christian’s email: christian.witz@simvantage.com
Free 5-day email course, The CMC Failure Chain: the five recurring CMC mistakes that put your promising program at risk → Get it here
Support the show

Biotech founders often pour everything into building the “perfect” product only to realize their real customers have walked out the door. Chasing perfection can burn money and stall even the most promising CMC innovations.
In this episode, David Brühlmann continues his conversation with biotech entrepreneur and investor John Bonham-Carter. John shares his insights on the realities of building and scaling successful biotools companies, from the challenges of fundraising and the importance of authentic storytelling, to knowing when to stop perfecting a product and start selling.
Topics discussed:
How fundraising is less about money and more about the story, team, and real commitment behind a startup (02:33)
Practical advice for founders: obsess over the customer, not just the technology (07:14)
The dangers of spreading yourself too thin as a startup founder and lessons from parenting applied to startups (07:09)
Choosing business partners and collaborators whose skills complement your own—and making peace with imperfection (10:10)
John’s approach to building teams and why accepting mediocrity in some areas can lead to collective excellence (11:16)
The story behind John joining Stellion Biosystems, and what makes their cell counting technology different in the market (11:51)
Using creative, low-budget tactics for visibility—why John chose a lizard mascot for Stellion Biosystems (15:19)
Thoughts on when (if ever) to stop and the value of keeping multiple life and career doors open (17:26)
John’s main takeaway: “Try everything”—professional advice drawn from experience (and Zootopia) (19:01)
Smart insight: John leaves us with a simple yet powerful credo: “Try everything.” In biotech, that means embracing experimentation not just in the lab, but in business strategy, partnerships, hiring, and technology adoption. By collaborating, iterating, and listening closely to customers, you can grow, succeed, and—perhaps—build something that truly makes a difference. In a field where the only constant is change, remember: launch before you’re ready, find your people, and keep your story genuine.
Some ideas are ahead of their time; a few people make a career of being early. This is part bioprocess history, part founder's playbook: why the best technology doesn't automatically win, how to move a conservative industry, and when to sell rather than scale. To go further on both the technology and the business behind it:
Episodes 191 - 192: Process Intensification Secrets: A Process Engineer's Decision Framework with Andreas Castan
Episodes 183 - 184: From Lab to Market: Secrets to Commercializing Cutting-Edge Biotech Innovations with Chervee Ho
Episodes 259 - 260: Why Strong Science Isn't Enough to Get Funded: What Investors Actually Look For with Michael Rome
Episodes 165 - 166: Why Your Funding Pitches Fail Despite Brilliant Science (And How to Fix It)
Connect with John Bonham-Carter:
Website: www.stellion-biosystems.com
LinkedIn: www.linkedin.com/in/johnbc
Free 5-day email course, The CMC Failure Chain: the five recurring CMC mistakes that put your promising program at risk → Get it here
Support the show

Biotech loves talk of disruptive technology, but few have repeatedly shifted the industry's direction. This episode of the Smart Biotech Scientist Podcast focuses on an idea once dismissed as a fool's game: process intensification through perfusion—now the backbone of leading biomanufacturing platforms.
Meet John Bonham-Carter, a serial entrepreneur whose fingerprints are on some of biotech's most transformative tools. From putting the once-ignored ATF system and perfusion on the global stage to pushing intensified cell therapy bioprocessing with ERBI, John's story isn't about chasing the next big exit. Instead, it's about spotting unmet needs and building and selling biotools companies more than once.
Topics discussed:
The story behind the ATF system, and how John Bonham-Carter and his collaborators convinced a conservative industry to adopt perfusion (04:43)
Early career influences, including family ties to bioprocess equipment manufacturing (05:03)
Reflections on the biotech industry’s culture of collaboration and the dual motivation to deliver medicines and achieve commercial success (07:18)
Realities of scaling a startup, trading income for equity, and the role of persistence in sales (09:34)
Lessons learned from global travel and building professional networks in biotech (10:16)
The importance of recognizing what drives different biotech companies to adopt new technology (12:25)
The transition from ATF to co-founding Erbi, a bioprocessing startup focused on small-volume cell therapy (19:05)
Strategic acquisitions: experiences of being acquired by Repligen and Merck Millipore (22:50)
Advice for founders on whether to build a company for exit or long-term operation (23:07)
The limits of leading with technology, and why customer understanding is critical to success (26:10)
Smart insight: For founders, John Bonham-Carter offers practical guidance anchored in self-awareness. Should you build a company for the long haul or for acquisition? The answer: “There isn’t really a right answer...it is, what is the life you want to lead?” Some entrepreneurs thrive at the scale of ten-person teams and relish the handoff to a strategic acquirer. Others yearn to build and steer a 200-person enterprise. Regardless, serving customers and employees well, and being attuned to the market’s shifting demands, matter most. Exit opportunities arise from building value and strategic fit—not from fixating on selling out.
Some ideas are ahead of their time; a few people make a career of being early. This is part bioprocess history, part founder's playbook: why the best technology doesn't automatically win, how to move a conservative industry, and when to sell rather than scale. To go further on both the technology and the business behind it:
Episodes 191 - 192: Process Intensification Secrets: A Process Engineer's Decision Framework with Andreas Castan
Episodes 183 - 184: From Lab to Market: Secrets to Commercializing Cutting-Edge Biotech Innovations with Chervee Ho
Episodes 259 - 260: Why Strong Science Isn't Enough to Get Funded: What Investors Actually Look For with Michael Rome
Episodes 165 - 166: Why Your Funding Pitches Fail Despite Brilliant Science (And How to Fix It)
Connect with John Bonham-Carter:
Website: www.stellion-biosystems.com
LinkedIn: www.linkedin.com/in/johnbc
Free 5-day email course, The CMC Failure Chain: the five recurring CMC mistakes that put your promising program at risk → Get it here
Support the show

What if building a world-class biotech company didn’t require owning a single piece of manufacturing equipment or even a lab of your own?
Most startups obsess over bricks, mortar, and stainless steel. Not Sandra Núñez. She’s challenging the status quo as CEO of Amela Biosciences by running a “virtual plant” model: zero in-house production, everything outsourced, and agility baked into every decision. It’s a bold experiment in redefining what a biotech company can look like. One that’s already delivering real, animal-free products to customers today.
Topics discussed:
Key considerations and pitfalls in tech transfer from academic labs to external CDMO partners (02:34)
The reasoning behind choosing a virtual plant model with no in-house manufacturing (04:57)
Criteria for selecting external manufacturing partners, including technical capabilities and cultural fit (06:28)
Stakeholder communications and managing misconceptions about outsourced manufacturing (07:44)
Process development challenges when scaling products for commercial use, including impurity profile and scalability of purification methods (08:53)
Early preparations for future GMP manufacturing and building a foundation for regulatory compliance (11:20)
The impact of regulatory shifts (like the FDA Modernization Act 2.0) on manufacturing strategy and product reproducibility (12:47)
Hopes for the company’s future role in the transition to animal-free and regenerative medicine (14:19)
Practical advice for startup founders considering a leap from corporate biotech to entrepreneurship (15:09)
Reflections on the importance of addressing batch-to-batch variability and building reproducible systems (16:40)
Smart insight: Don’t accept batch-to-batch variability. Reproducibility is non-negotiable. Batch-to-batch variability, whether in raw materials or process design, is a critical risk that forward-thinking should design out, not accept as inevitable. As Sandra concludes, reproducibility isn’t just a lab problem, it’s a company-building problem, one that shapes strategy, manufacturing partnerships, and regulatory success.
Here are four episodes that pick up the same threads: animal-free matrices, reproducibility by design, and building a biotech without a factory:
Episodes 271 - 272: From Static Scaffolds to Dynamic Matrices: Hydrogels for Animal-Free 3D Cell Culture with Jan Hunik and Matt Baker
Episodes 221 - 222: From 2D Cultures to Advanced 3D Cell Models for Preclinical Research with Catarina Brito
Episodes 275 - 276: From Lab-Scale Molding to GMP: Manufacturing a Collagen Implant for the Clinic with Eva-Maria Balet
Episodes 279 - 280: Why Nanovesicles Outperform Exosomes: Scalable Drug Delivery Beyond Injectable Vaccines with Christopher Locher
Connect with Sandra Núñez:
Website: www.amelabiosciences.com
Company LinkedIn: www.linkedin.com/company/amela-biosciences-ag
Sandra’s LinkedIn: www.linkedin.com/in/sandra-nunez-ch
Sandra’s email: s.nunez@amelabiosciences.com
Free 5-day email course, The CMC Failure Chain: the five recurring CMC mistakes that put your promising program at risk → Get it here
Support the show