2015年，兩位普林斯頓大學的博士生尼爾?奧佐諾夫和亞歷山大?勞瑞斯塔尼申請到了舊金山的生物技術加速器項目IndieBio。他們的目標是設計一種能產生大量蛋白質的微生物，以滿足一些特殊用途。他們當時認為，這種微生物或許能應用于制藥科學，比如用來制造胰島素等。

不過Indiebio加速的聯合創始人萊恩?貝森科特卻鼓勵道，他們應該考慮如何將這種蛋白質作為一種產品應用于食品領域。

貝森科特解釋道：“胰島素已經不新鮮了，現在其他人也能做胰島素，所以你必須轉型。”那么他們轉向了什么開創性的領域？答案是不含動物成分的明膠。明膠一般是用膠原蛋白制成的，而膠原蛋白一般來自豬、牛等動物的骨骼和皮膚等組織。他們選擇的這個新方向，也令本身就是素食者的貝森科特興奮不已。

生物科技這門科學原本是大型制藥企業的專寵，主要用來生產一些高價值的商品——比如胰島素等。但隨著DNA測序等生物技術的相關成本大幅下降，生物科技的研究對象也越發多樣化。同時生物燃料的興起也進一步促進了行業經濟的重新洗牌。幾乎一夜之間，生物反應器等設備的價格已經不再高不可攀了。因此，生物科技也不再局限于制造高價格的藥品，而是也可以制造食品這樣的大宗產品。

奧佐諾夫和勞瑞斯塔尼最后創辦了一家名叫Geltor的公司，它也是舊金山灣區少數采用發酵技術生產動物制品的創業公司之一。這家公司的創新性在于，他們生產的動物制品并不需要宰殺任何動物。另外，還有兩家由IndieBio支持的創業公司Clara Foods和Perfect Day也在利用類似的技術生產蛋白和乳蛋白。他們的生產工藝中需要使用細胞，但他們的最終產品中卻并沒有細胞，這種產品也稱為非細胞產品。（相比之下，Memphis Meat和MosaMeat等創業公司則主要研究細胞產品，也就是最終產品中包含細胞本身。）

當你走進一家研究這種細胞農業技術的創業公司時，你首先會發現他們的實驗室里彌漫著一股濃濃的發酵的味道。Clara公司的CEO阿圖羅?埃利桑多解釋道，酵母菌就像一座座小工廠，只要對它們進行“編程”，它們幾乎能造出任何東西，而且它們對整個發酵過程至關重要。

在這些實驗室里，科學家會從基因上對酵母菌或細菌進行修改，然后用糖分喂養它們，使它們的分子結構變得與膠原蛋白（用來制作明膠）或是酷蛋白和乳清蛋白（用來制作奶酪）完全相同。在發酵過程的最后，這些蛋白質會從混合物中提純出來。

最后的產品雖然用基因工程做出來的，但科學家并不認為它是一種轉基因生物，因為科學家們會把所有轉基因的酵母菌都清除掉。那么消費者會不會對此感到不適呢？對此，奧佐諾夫表示：“自然界生產膠原蛋白的方式其實要比這惡心得多。”

本文的另一版本載于2017年12月15日刊的《財富》雜志。

In 2015 Nick Ouzounov and Alexander Lorestani applied to the San ?Francisco–based biotech accelerator IndieBio. The two Princeton Ph.D.s had an idea for a way to engineer a microbe that could build vast amounts of protein designed for specific functions. They envisioned that it could have biopharma applications, such as being used to produce insulin.

But Ryan Bethencourt, who cofounded the accelerator, instead encouraged them to focus on using the protein for a product in the food space.

“Insulin was an old play. There are other people who can make insulin,” Bethencourt explains. “You have to be transformative.” The groundbreaking idea that they went with? Animal-free gelatin, which in its regular form is derived from collagen—a material that is typically made from the bones, skin, and tissues of cows and pigs. The reaction from Bethencourt, who is himself a vegan: “Brilliant.”

Biotech was once a tool reserved for pharmaceutical giants making high-value goods—just like insulin. But there’s a shift that’s taken place as biotech’s associated costs, such as DNA sequencing, have plummeted. The biofuel bust has helped further reshuffle the economics of the industry. All of a sudden bioreactors and other equipment have become available for cheap. The result is that biotech is no longer reserved just for producing high-priced medicine but could start to make sense for commodity products like food.

Ouzounov and Lorestani ended up cofounding Geltor, one of a handful of Bay Area startups using a biotech process called fermentation to make animal products. The transformative part is they don’t need the animals to do it. Fellow IndieBio-backed startups Clara Foods and Perfect Day are using the method to make egg whites and milk proteins, respectively. They use cells as part of their production method but there are no cells in the end result—what’s called an acellular product. (In contrast, startups Memphis Meats and MosaMeat are working on cellular products, in which the end result contains the cells themselves.)

One obvious tell that you are visiting a startup working on this form of cellular agriculture is the yeasty smell that hits you as you walk into one of their labs. Yeast are like little factories, explains Clara CEO Arturo Elizondo. They can be programmed to make essentially anything and are critical to fermentation.

In these labs scientists genetically modify yeast or bacteria and feed them sugars to produce a protein that’s molecularly identical to collagen (in the case of gelatin) or casein and whey (for cheese). At the end of the process that protein is purified out of the mixture.

The end result is made using genetic engineering, but is not considered a genetically modified organism since scientists remove the altered yeast. Will consumers be freaked out by the process? “The natural way of making gelatin is much more disturbing,” says Ouzounov.

A version of this post appears as a sidebar in the article “Silicon Valley and the Search for Meatless Meat” in the Dec. 15, 2017 issue of Fortune.