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A meaty question
IF YOU have ever longed for a meat substitute that smelt and tasted like the real thing, but did not involve killing an animal, then your order could be ready soon. Researchers believe it will soon be possible to grow cultured meat in quantities large enough to offer the meat industry an alternative source of supply.
Growing muscle cells (the main component of meat) in a nutrient broth is easy. The difficulty is persuading those cells to form something that resembles real meat. Paul Kosnik, the head of engineering at a firm called Tissue Genesis, is hoping to do it by stretching the cells with mechanical anchors. This encourages them to form small bundles surrounded by connective tissue, an arrangement similar to real muscle.
Robert Dennis, a biomedical engineer at the University of North Carolina, believes the secret of growing healthy muscle tissue in a laboratory is to understand how it interacts with its surroundings. In nature, tissues exist as elements in a larger system and they depend on other tissues for their survival. Without appropriate stimuli from their neighbours they degenerate. Dr Dennis and his team have been working on these neighbourly interactions for the past three years and report some success in engineering two of the most important-those between muscles and tendons, and muscles and nerves.
At the Touro College School of Health Sciences in New York, Morris Benjaminson and his team are working on removing living tissue from fish, and then growing it in culture. This approach has the advantage that the tissue has a functioning system of blood vessels to deliver nutrients, so it should be possible to grow tissue cultures more than a millimetre thick-the current limit.
Henk Haagsman, a meat scientist at the University of Utrecht in the Netherlands, is trying to make minced pork from cultured stem cells with the backing of Stegeman, a sausage company. It could be used in sausages, burgers and sauces.
But why would anyone want to eat cultured meat, rather than something freshly slaughtered and just off the bone? One answer, to mix metaphors, is that it would allow vegetarians to have their meatloaf and eat it too. But the sausagemeat project suggests another reason: hygiene. As Ingrid Newkirk of PETA, an animalrights group, puts it, "no one who considers what's in a meat hot dog could genuinely express any revulsion at eating a clean cloned meat product."
Cultured meat could be grown in sterile conditions, avoiding Salmonella, E. coli, Campylobacter and other nasties. It could also be made healthier by adjusting its composition-introducing heartfriendly omega-3 fatty acids, for example. You could even take a cell from an endangered animal and, without threatening its extinction, make meat from it. Giantpanda steak, anyone?
一个食用肉类的问题
如果你曾经希望能有一种肉类的替代品，闻起来和尝起来都像真的，但是并不是通过杀害动物得来的，那么你的要求将在不久之后得到满足。研究者相信培养肉类马上就可能大量生产，作为一种供给的替代品供应肉类工业。
在富有营养的肉汤中使瘦肉细胞成长（肉类的主要成分）是一件容易的事情。困难在于使这些细胞能组成像真的肉类那样的东西。一个名为组织创世纪公司的工程师的首领Paul Kosnrk希望利用机械锚定技术来拉伸细胞。这种技术刺激细胞形成被结缔组织环绕的细小肌肉束，和真的肌肉的组织形式相类似。
北卡罗来纳州立大学的生物医学工程师Robert Dennis相信，在实验室中培养出健康的肌肉组织的秘密在于理解肌肉组织是怎样和环境相互作用的。自然界中，肌肉组织作为一个更大的机体组织的基础而存在，并且依靠这个机体中的其他组织而存在。如果没有它们的邻居适当的刺激，它们就将退化。Dennis博士和他的团队在过去的三年里研究了这些相似的组织的相互作用，并且发表了在两个最重要的生物工程学方面成功的研究--肌肉组织和结缔组织的关系，以及肌肉组织和神经组织的关系。
在纽约托罗大学的保健科学学院，Morris Benjaminson和他的团队正在研究怎样从鱼的身体上取下活体组织，然后人工培养。这种方法的优点是，组织有一个输送养分功能的血管系统，这样它就可以在人工环境中生长出超过厘米数量级的厚度--这也是现今生长的极限。
荷兰Utrecht 大学的肉类科学家Henk Haagsman正在试图从Stegeman香肠公司得到对其碎块猪肉的支持，这些猪肉块源于人工生长的细胞。这种材料可以用到香肠，汉堡和寿司中去。
然而，为什么一个人想要食用人工的，而不是刚宰了并剔骨后的新鲜的肉类呢？含糊地说，这样可以让素食者们拥有并享用他们理想的肉块。但是香肠肉类工程还有另外一个原因：卫生。正如动物权利组织PETA的Ingrid Newkrik指出的：想到热狗里面的肉原来是什么时，没有人会在心底里反对食用干净的克隆肉类制品。
人工肉类可以在无菌环境中培养起来，以避免沙门氏菌，大肠杆菌，弯曲状杆菌以及其他脏东西。也可以通过对成分的调节来使得其更加健康--例如，引进有益心脏的omega3型脂肪酸。在丝毫不威胁到物种种群的情况下，你甚至还可以从快要灭绝的动物身上取下细胞，用这些细胞来培养成肉。大熊猫肉排，还有呢？
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