Page 19 - Science Focus (Issue 017)

「種」出人造肉 ─

未來的肉類生產方法？

Although cultured meat may sound like a great
replacement of meat production at first glance,
further refinements have yet to be made to increase
the sustainability of the process. Cultured meat start-
ups around the world are looking into solutions to
tackle the current longstanding problems. First,
growing meat (which contains muscle and fat cells)
in the laboratory requires vast amounts of fetal bovine
serum (FBS) — the conventional supplement in growth
medium used for culturing cells in the lab, which Europe and Southeast Asia, with a focus on slaughter-
contains growth factors, proteins, vitamins and other free methods of meat production. The rate of consumer
substances required for optimal cell growth. It is also acceptance for cultured meat is also encouraging. The
subject to widespread criticism and negativity, since ability to produce cultured meat holds much excitement
it is extracted from the heart of calves by a cardiac even for us, as it means we can delight in the possibility
puncture without anesthesia, following the slaughter of of consuming delicacies from sashimi-grade fish to
pregnant cows [8]. Since FBS is a byproduct of factory plump Peking duck, without harming animals nor the
farming, ongoing research is carried out on looking environment.
for serum-free alternatives to grow cultured meat. A
study conducted by Fujita et al. showed the promise of 1 Scaffold: A structure that provides proper surroundings and
using serum-free media for growing myoblast cells [9]. mechanical support for the cells to grow onto it. It also guides
Myoblasts are descendants of satellite cells. They have the tissue to grow into the desired shape.
the ability to fuse to form myotubes, a multi-nucleated, 2 Chitosan: A polymer derived from chitin, a substance which
elongated structure which indicates they are on the right makes up the shells of crustaceans, e.g. crabs and shrimps.
developmental track towards differentiating into mature
muscle cells. Some scientists are venturing towards the
search for suitable plant-derived growth supplements to
replace FBS for cell culture. Such research paves the way
for the possibility of cultured meat to be commercialized. 在史前時期，為了果腹，獵人製造武器協助他們狩
Another problem lies in the scaffold required for the 獵。隨著時間的推移，人類的知識變得豐富，帶來了畜牧、
orderly three-dimensional growth of cells — another 選擇育種和基因改造肉類。為了應付現今社會不斷膨脹的人
hurdle for scientists in the cultured-meat industry to
overcome for easier meat production. IntegriCulture, a 口所帶來的肉類需求，透過工廠化飼養（factory farming）
Japanese biotech start-up which focuses on developing 取得食用肉變成了肉類行業的常態。可是，這個過程少不免
cell-based meat, has suggested the possibility of using 會為動物帶來痛苦，亦為環境帶來沉重的負擔。肉類生產
edible materials, such as sponge collagen, chitosan
2
and chitin, as scaffold [10]. In fact, earlier in 2009, 出乎意料地佔用了地球陸地面積（被冰覆蓋的陸地除外）的
scientists have found the microporous collagen-chitosan, 26% [1]、全球淡水用量的 27% [2] ，以及佔人為溫室氣體
a material prepared by combining collagen and 排放的 18% [3]。僅是供人類食用而被屠宰的動物每年就有
chitosan, to be a suitable scaffold for the proliferation of
fibroblasts, a type of connective tissue cell [11]. Research 740 億隻 [4]。據估計，生產每公斤牛肉需要 25 公斤穀物和
from the Chinese University of Hong Kong has also 15,000 公升水 [5]；為了騰出空間飼養牛隻，人們還經常會
shown that the collagen-chitosan scaffold enhanced 在亞馬遜雨林等地區進行伐林活動 [6]。然而，動物產品只佔
the growth and division of rat stem cells from their bones
[12]. Although this mixture of scaffold has yet to be tested 人類攝取熱量的 18% 和攝取蛋白質的 37% ，可見這是一
amongst satellite cells, it is undoubtedly an area that 個低效率的食物生產系統 [7]。當氣候變化、資源稀少和環
deserves more investigation.
境污染已經變成世界今天切身的問題時，我們需要找尋更多
While there is still a ways to go before cultured meat 創新的方法避免工廠化飼養所導致的環境問題。人造肉的誕
could become the norm for satiating meat lovers around
the world, the progress made in this industry thus far is 生有望能使工廠化飼養成為歷史 ── 它是一個更環保、可持
promising! Start-ups are blooming in the United States, 續和有益的替代方案。

17