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Kangaroo fecal microbes could reduce methane from cows
Baby kangaroo feces might help provide an unlikely solution to the environmental problem of cow-produced methane. A microbial culture developed from the kangaroo feces inhibited methane production in a cow stomach simulator in a Washington State University study.
After researchers added the baby kangaroo culture and a known methane inhibitor to the simulated stomach, it produced acetic acid instead of methane. Unlike methane, which cattle discard as flatulence, acetic acid has benefits for cows as it aids muscle growth. The researchers published their work in the journal Biocatalysis and Agricultural Biotechnology.
"Methane emissions from cows are a major contributor to greenhouse gases, and at the same time, people like to eat red meat," said Birgitte Ahring, corresponding author on the paper and a professor in with the Bioproducts, Sciences and Engineering Laboratory at the WSU Tri-Cities campus. "We have to find a way to mitigate this problem."
Reducing the burps and farts of methane emissions from cattle is no laughing matter. Methane is the second largest greenhouse gas contributor and is about 30 times more potent at heating up the atmosphere than carbon dioxide. More than half of the methane released to the atmosphere is thought to come from the agricultural sector, and ruminant animals, such as cattle and goats, are the most significant contributors. Furthermore, the process of producing methane requires as much as 10% of the animal's energy.
Researchers have tried changing cows' diets as well as giving them chemical inhibitors to stop methane production, but the methane-producing bacteria soon become resistant to the chemicals. They also have tried to develop vaccines, but a cow's microbiome depends on where it's eating, and there are far too many varieties of the methane-producing bacteria worldwide. The interventions can also negatively affect the animals' biological processes.
The WSU researchers study fermentation and anaerobic processes and had previously designed an artificial rumen, the largest stomach compartment found in ruminant animals, to simulate cow digestion. With many enzymes that are able to break down natural materials, rumens have "amazing abilities," said Ahring, who is also a professor in the Gene and Linda Voiland School of Chemical Engineering and Bioengineering and in Biological System Engineering.
Looking to investigate how to outcompete the methane-producing bacteria in their reactor, Ahring learned that kangaroos have acetic acid-producing, instead of methane-producing, bacteria in their foregut. Her students tracked down some kangaroos, took samples and learned that the specialized acetic acid-producing process only occurred in baby kangaroos—not in adults. Unable to separate out specific bacteria that might be producing the acetic acid, the researchers used a stable mixed culture developed from the feces of the baby kangaroo.
After initially reducing the methane-producing bacteria in their reactor with a specialized chemical, the acetic acid bacteria were able to replace the methane-producing microbes for several months with a similar growth rate as the methane-producing microbes.
While the researchers have tested their system in the simulated rumen, they hope to try it on real cows sometime in the future.
"It is a very good culture. I have no doubt it is promising," Ahring said. "It could be really interesting to see if that culture could run for an extended period of time, so we would only have to inhibit the methane production from time to time. Then, it could actually be a practice."
注释：
Feces:
表示“粪便 ”，means " solid excretory product evacuated from the bowels“，如：Please pick up dog feces from camps and trails. 请从帐蓬和小道上拾起狗的排泄物。
Fecal: adj
表示“ 排泄物的；渣滓的”，means "of or relating to feces “，如：After the doctor took a fecal sample, he sent it to the laboratory. 医生取了便样后，就把便样送进了化验室。
Methane: n
表示“ 甲烷； ”，means "a colorless odorless gas used as a fuel “，如：Cattle release methane when they digest their food. 牛在消化食物时,会释放出甲烷。
Microbial: adj
表示“ 微生物的 ”，means " of or involving or caused by or being microbes“，如：These compounds inhibit microbial growth. 这些化合物能抑制微生物的生长。
Inhibit: v
表示“抑制 ”，means " hold back“，如：You should inhibit wrong desires and impulses. 你应当抑制不正当的欲望和行动。
Inhibitor: n
表示“ 抑制物；”，means "a substance that retards or stops an activity “，如：Mouldproof wall paper, join mould inhibitor. 防霉墙纸，加入防霉剂。
Flatulence: n
表示“ 肠胃气胀 ”，means "a state of excessive gas in the alimentary canal “，如：One symptom of chronic gastritis is flatulence. 慢性胃炎的症状之一就是气胀。
Acetic:
表示“ 酸的 ”，means "relating to or containing acetic acid “，如：The wine in him has almost melted acetic acid. 他一肚皮的酒几乎全化为了醋酸。
Biocatalysis:
表示“生物催化 ”，如：Microbial reactions play key roles in biocatalysis and biodegradation. 在生物催化和生物降解中微生物反应起了关键的作用。
Mitigate: v
表示“ 减轻；缓和 ”，means "lessen or to try to lessen the seriousness or extent of; “，如：Her words mitigated my suffering. 她的话减轻了我的痛苦。
burp: n
表示“ 饱嗝儿 ”，means "a reflex that expels gas noisily from the stomach through the mouth “，如：A burp is not an answer. 打嗝不是答案。
fart: n
表示“ 屁 ”，means "a reflex that expels intestinal gas through the anus “，如：So, just because of putting a fart, I became a sceptic.
就这样，仅仅因为放了一个屁，我就成了一个怀疑论者。
ruminant: adj
表示“反刍的； ”，means "related to or characteristic of animals of the suborder Ruminantia or any other animal that chews a cud “，如：The teeth of the ruminant animals are specialised, unlike those of a carnivorous animal. 反刍家畜的牙齿很特殊，完全不同于肉食动物。
microbiome: n
表示“ 微生物组 ”，means "A microbial biome, such as the community of microbes within the human gut “，如：Jeremy Nicholson of Imperial College London is exploring both the microbiome and the metabolome. 伦敦帝国理工学院的JeremyNicholson分别对该微生物组和代谢组进行探究。
anaerobic: adj
表示“ 厌氧的 ”，means "living or active in the absence of free oxygen “，如：The anaerobic exercise is good for your muscle. 无氧运动有助于锻炼肌肉。
rumen: n
表示“ 瘤胃(反刍动物的第一胃)”，means "the first compartment of the stomach of a ruminant “，如：The cow gets rid of the gases formed in the rumen by belching at frequent intervals. 牛靠经常的打嗝以释放瘤胃中形成的气体。
outcompete: v
表示“ 胜过 ”，means "compete more than “，如：Grasses are well adapted to fire, being able to resprout quickly from their roots and thus outcompete tree seedlings. 草很适应火烧，能够迅速地从它们的根部重新发芽生长，于是就胜过了树苗。
gut: n
表示“肠,内脏 ”，means " intestine，he organs in and around the stomach“，如：It takes several hours for food to pass through the gut. 食物经过肠子需要几个小时
foregut: 表示“前肠 ”
中文简要说明：
畜牧业的甲烷排放问题，是科学家一直想要解决的，目前的主流方法是调查饲料的配方，希望牛的排气可能少一些。牛的排气源自肠内细菌，因此也有科学家想要为牛只「改善体内菌丛」，他们在袋鼠的粪便中找到理想的细菌，不但可以减少甲烷的产生，还可能使牛只更长肉。
物理学网(phys.org)报导，很难相信，牛只畜牧业是相当严重温室气体排放来源，由于牛奶与牛肉的供应需求量很大，全球牛只的打嗝和放屁产生的甲烷，总体排放量可不是闹着玩的。据统计，释放到大气中的甲烷，有一半以上来自农业部门，而甲烷是第二大温室气体者，每单位的升温的能力，大约是二氧化碳的 30 倍。
牛之所以会排放大量甲烷，这要从它们的消化说起。牛是典型的反刍动物，其特点就是有4个胃，分别是瘤胃、蜂窝胃、重瓣胃与皱胃。其中，瘤胃是最大的一个，它就个像个发酵桶，草料在胃里被大量的细菌分解着。然而分解的过程就会产生大量的甲烷。
研究人员一直试图解决这个发酵过程，好改善甲烷的产生量。先前研究曾尝试改变牛的饮食，并给它们化学抑制剂来阻止甲烷的产生，但是，产牾甲烷的细菌很快就会对这些化学物质产生抗药性。接下来，科学家也曾经尝试开发疫苗，但是，这只会杀死牛肚里的细菌，上一段提到，那些细菌在帮助牛消化草料，而且会产生甲烷的细菌种类太多，刻意干预可能产生负面影响。
华盛顿州立大学的研究团队决定先创造一个人造瘤胃，以研究发酵和厌氧过程。该计研发人造瘤胃的阿林教授(Birgitte Ahring)表示，我们将瘤胃中的酵素给放进人造瘤胃里，并保持牛的体温，以形塑一个类似瘤胃的环境。
经过几年的实验，研究团队找到袋鼠的粪便，袋鼠是一种植食动物，肠胃也要消化草料。团队发现，袋鼠粪便培养出的细菌，其分解作用的副产品竟然不是甲烷，而是乙酸，它也叫醋酸，也就是醋的主要成份。更好的是，醋酸对牛有益，因为它有助于肌肉生长。
阿林教授发现，那种细菌源自袋鼠的前肠，但是在后续研究发现，这种专门产生醋酸的过程，只发生在小龄袋鼠身上，而不是成年袋鼠身上。由于无法分离出可能产生乙酸的特定细菌，研究人员只好收集袋鼠宝宝的粪便，然后得出混合多种细菌的培养物。
接下来，研究团队刻意把甲烷细菌给去掉，将产醋酸细菌放到模拟瘤胃中，证实在后续的几个月内，产醋酸细菌能够在模拟瘤胃中持续存活。因此在理论上，它应该也能在牛胃中生存，然后彻底取代甲烷细菌。当然，牛能不能适应这种细菌提的帮助消化还不得而知，团队希望在不久之后，在真正的乳牛身上进行试验。
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