研究發現，一種會在自然環境中形成有毒優養化的海洋浮游藻類，可被利用來製造生物乙醇的原料，有機會成為交通工具燃料的新來源。
美國德拉瓦大學科學家發現，赤潮異彎藻（學名Heterosigma akashiwo）尤其適合用來製造生物乙醇原料，因為這種藻類生存在高一氧化氮的環境，而一氧化氮是火力發電廠排放之煙道氣的成份之一。
「赤潮異彎藻在一氧化氮環境中非常活躍，不但成長速度增加一倍，細胞也比在沒有一氧化氮的環境下更大。」德拉瓦大學地球海洋環境學院海洋生物學副教授Kathryn Coyne指出。
事實上，當施以和煙道氣中二氧化碳及一氧化氮含量相同的混和氣體時，赤潮異彎藻細胞成長非常快速。赤潮異彎藻增殖的時候會產生大量碳水化合物，這些碳水化合物能被轉換成生物乙醇。
優養化專家Coyne指出，赤潮異彎藻存在於世界各地的自然環境中。
Coyne的團隊發現，赤潮異彎藻在煙道氣中增殖時產生的碳水化合物量比在空氣中增殖時要多得多，而且赤潮異彎藻可能具有特殊能力，能中和威脅人體和環境的一氧化氮氣體。這讓Coyne的團隊開始研究這種藻類是否也能在二氧化碳中成長而不被煙道氣中高含量的一氧化氮殺死。
根據美國有毒物質和疾病登錄局的資料，一氧化氮氣體具有刺激性的甜味，室溫下雖不可燃，但卻是「毒性最強的氮氧化物」之一。汽機車排放廢氣，煤、石油和天然氣的燃燒，電弧焊接、電鍍、雕刻及炸藥爆破等過程都會釋放出氮氧化物。空氣中含有少量氮氧化物就能刺激眼睛、鼻子、喉嚨和肺部。吸入大量氮氧化物可能致命。
在煙道氣內，赤潮異彎藻不需一氧化氮以外的氮來源就可生長，因此培養赤潮異彎藻生產生物燃料將是相當節省成本的方法。
「赤潮異彎藻此特性可省下45%的能量輸入成本。」Coyne指出。
Coyne表示，此技術若持續發展，將可望成為減少碳污染的解決方案，有助實踐美國總統歐巴馬上周針對氣候變遷發表的談話。
「我們的目標不只是製造生物燃料，也將利用此藻類發展出緩解工業煙道氣毒性的生物修復技術。」Coyne說。
A species of swimming marine algae that forms toxic algal blooms in the natural environment can be harnessed to grow a feedstock for bioethanol to fuel vehicles.
The algae Heterosigma akashiwo are uniquely suited for this task because they can live and thrive in an atmosphere high in nitric oxide, a component of the flue gases emitted by fossil-fueled power plants, scientists at the University of Delaware have demonstrated.
“The algae thrive on the gas,” said Kathryn Coyne, associate professor of marine biosciences in the university’s College of Earth, Ocean, and Environment. “They grow twice as fast and the cells are much larger in size compared to when growing without gas treatment.”
In fact, the microscopic cells grow rapidly on a gas mixture that has the same carbon dioxide and nitric oxide content as flue gas. As the algae grow they make large amounts of carbohydrates, which can be converted into bioethanol.
Coyne and her team have found a large increase in carbohydrates when the algae grow on flue gas as compared to air.
Heterosigma akashiwo is naturally found worldwide, says Coyne, an expert in algal blooms.
She discovered that the species may have a special ability to neutralize nitric oxide, a harmful gas that poses threats to environmental and human health.
The U.S. Agency for Toxic Substances describes nitric oxide as a sharp sweet-smelling gas at room temperature that is nonflammable but is one of the “most toxicologically significant nitrogen oxides.”
Nitrogen oxides are released to the air from the exhaust of motor vehicles, the burning of coal, oil, or natural gas, and during processes such as arc welding, electroplating, engraving, and dynamite blasting.
Low levels of nitrogen oxides in the air can irritate the eyes, nose, throat, and lungs. Breathing high levels of nitrogen oxides can be fatal.
The characteristic ability of this algae to neutralize nitric oxide and grow on a gas containing it prompted Coyne and her team to investigate whether it could grow on carbon dioxide without getting killed off by the high nitric oxide content in power plants’ flue gas.
The algae need no other nitrogen sources beyond the nitric oxide in flue gas to grow, a cost-saving method of raising Heterosigma akashiwo for biofuel production.
“This alone could save up to 45 percent of the required energy input to grow algae for biofuels,” Coyne said.
Development of their technology could support a national focus on carbon pollution reduction that would complement President Barack Obama’s major speech last week on climate change, Coyne said.
“Our approach to the issue is to not just produce biofuels,” she said, “but to also use this species for bioremediation of industrial flue gas to reduce harmful effects even further.”
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