To explain how his San Leandro company Geltor makes vegan gelatin based on the very proteins found in animal bones and skin, co-founder and CEO Alexander Lorestani describes what he calls a “microbial factory.”

Perfect Day Foods in Berkeley, which is working on an animal-free version of cow milk, likens its production method to brewing beer — except that these meat breweries make protein rather than alcohol.

Both companies are practitioners of yeast-based fermentation. Like cultured meat, this method of making protein is difficult to envision — or to even think of as something that resembles food production. But in the Bay Area, several companies are in the development phase of producing milk, egg whites and gelatin using yeast-based fermentation to create proteins that are chemically identical to the original, yet animal free. Some could be in stores as early as next year.

They’re taking advantage of a method that’s been in production since 1990 to make vegetarian rennet, used in the majority of the world’s hard cheese.

The process starts with scientists using bioengineering to introduce protein genes to yeasts to create the desired protein during fermentation, though the genetically engineered yeast is filtered out of the final product.

“We order the sequences for these genes and have them deliver them in a little tube from a company that prints DNA,” says Geltor’s Lorestani. The microbes go into a fermentation tank, are fed with nutrients and then reproduce in (hopefully) large quantities.

“If you were to jump in with scuba gear, you would be swimming around in a mix of pure protein and the cells that have made them,” says Lorestani, a molecular biologist and vegetarian who is currently developing the product with his team at Lawrence Berkeley National Lab.

The proteins brewing in the Berkeley tanks of Perfect Day Foods, which is developing animal-free milk and other similar dairy products, are casein and whey, made with a yeast they named Buttercup. They’re still working on the final recipe for the full beverage, but after they filter the protein from the yeast, they will add vitamins and minerals, a nonlactose sugar (to avoid allergens), and some kind of plant-based fat for richness without cholesterol.

“There’s a delicate balance. Obviously we’re making sure everything is as healthy and sustainable as possible, while understanding that that magic of dairy is not from a very healthy fat,” says Ryan Pandya, Perfect Day Foods co-founder and CEO.

In addition to being vegan and free of allergens, Pandya says the milk should be less expensive than cow milk because it relies on fewer resources. The question remains how similar to milk it will taste.

Geltor is hoping to replace the traditional gelatin that gives chew to gummy bears and shape to Yoplait yogurt and Jell-O pudding, and is used widely in medicines, cosmetics and medical research. Lorestani says many producers are interested in vegan gelatin but they don’t want to sacrifice texture. Plant-based substitutes like agar-agar don’t make products as consistently firm or chewy.

“The opportunity to get something that is molecularly and functionally identical (to animal gelatin) is really exciting for them,” Lorestani says.

The company plans to send samples to large manufacturers this summer for research and development. The product could be on the market within three years.