Intro

I want to understand why cultivated meat isn't more successful. Why are people so bearish on it? Why isn't it already competing with factory-farmed meat? What are the big bottlenecks?

To answer any of these questions, I first need to lay out the basic process... that's the goal of this post.

The 3 main phases

The process of cultivating meat can be broken down into 3 high-level phases: the lab phase, the brewery phase, and the kitchen phase. As you might expect, these labels refer to the place where each phase actually happens. Here's what they each focus on:

Lab: isolating / refining the cells you want
Brewery: cultivating cells to reach a target volume
Kitchen: turning cultivated cells into a final consumable product

Of course, this tripartite structure is an oversimplification. There are actually two different methods you can use for the brewery phase – batch cultivation (aka fed-batch) and continuous cultivation (aka perfusion). Similarly, the kitchen phase varies a lot based on whether the end product is unstructured (e.g., ground meat) or structured (e.g., a steak). I've included breakdowns of all the different options and how they fit within the overarching 3-phase model below.

Lab

Biopsy the target animal. From this biopsy, isolate your desired cell type (e.g., stem cells, myoblasts, adipocytes, etc.). Each cell type has different tradeoffs (which I hope to dive into in a different post). Then, using some combination of selection, adaptation, and / or engineering, optimize your cell line for growth. The goal here is to develop cells that will grow quickly in suspension, that require only cheap media, and that can double many times before they run into issues. Once you've developed your cells, bank them: freeze thousands of vials for future cultivation.

Brewery

Batch

Thaw a vial of banked cells (for reference, this will usually be ~10-50 million cells in 1-2mL of solution) and use it to inoculate a ~50-200mL flask of media. Let it incubate for a few days. Then, move it through a chain of bioreactors that steadily increase in volume: start in a 1-2L bioreactor, then move to a 10-50L bioreactor, then to a 100-500L bioreactor and finally to a production-scale bioreactor (typically 2000-20,000L). Each of these bioreactors is basically identical: cells are kept warm, fed with growth media, agitated continuously, and provided with fresh oxygen (via sparging).

Once you hit your desired cell volume / density, harvest the full output: drain the production bioreactor into a centrifuge and use it to concentrate cells into a wet paste. Then, reset everything -- clean, sterilize and refill all the bioreactors with fresh media. Repeat this process for each new batch.

Continuous

This process starts similarly to the batch process -- you thaw a vial of banked cells and scale them up through a series of increasingly large bioreactors. The main difference here is that this process only happens once to get things started, rather than for every single batch. Once you achieve your target volume / density in the production-scale bioreactor, you start bleeding small portions off into a centrifuge for harvest. At the same time, you filter out any waste products and add fresh media in so that the unharvested portion can keep growing. I think of this like sourdough starter.

Now, even though this process doesn't need to be reset every batch, occasional resets are required for cleaning and maintenance. Whenever that happens, repeat the full process to get back to steady-state.

Kitchen

Unstructured

Take the wet cell paste and blend it with standard cooking ingredients (e.g., oils, binders, flavors, salt, colors, etc.) to achieve the desired taste, texture and nutrient profile. Then, use standard food-processing equipment to add shape. Finally, finish things off with cooking, pasteurization, and packaging as necessary.

Structured

This approach is significantly more complicated. Start by seeding cells onto an edible scaffold which acts as the physical structure for a cut of meat. Then, differentiate cells into the desired types (e.g., muscle fibers, fat cells, etc.). Allow the tissue to mature and develop structure. Finally, cook, pasteurize and package as necessary.

Conclusion

So, at a veryyyyyy high-level, this is how you cultivate meat! It's worth calling out a few things:

There are new, experimental methods for the brewery phase (e.g., packed-bed and hollow-fiber) that I have not included here
Historically, the vast majority of cultivated meat companies have aimed to create unstructured products. Structuring is an ongoing area of research