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Purifying Arsenic Polluted Water with Engineered Yeast . Matthew Alpert Shailendra Singh Shen-Long Tsai Dr. Ashok Mulchandani Dr. Wilfred Chen. Arsenic Toxicity. Common as As(V) and As(III). Arsenic Toxicity. Common as As(V) and As(III)
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Purifying Arsenic Polluted Water with Engineered Yeast Matthew Alpert Shailendra Singh Shen-Long Tsai Dr. Ashok Mulchandani Dr. Wilfred Chen
Arsenic Toxicity • Common as As(V) and As(III)
Arsenic Toxicity • Common as As(V) and As(III) • As(V) can be substituted for phosphate in the citric acid cycle, interfering with:
Arsenic Toxicity • Common as As(V) and As(III) • As(V) can be substituted for phosphate in the citric acid cycle, interfering with: • The reduction of NAD+ • ATP synthesis • Mitochondrial respiration
Arsenic Toxicity • As(III) acts as an endocrine disruptor by binding to hormone receptors
Arsenic Toxicity • As(III) acts as an endocrine disruptor by binding to hormone receptors • Disrupting the endocrine system has a serious impact on:
Arsenic Toxicity • As(III) acts as an endocrine disruptor by binding to hormone receptors • Disrupting the endocrine system has a serious impact on: • Metabolism • Tissue function • Growth and development
Hyperkeratosis Arsenic Toxicity
Hyperkeratosis Hypertension: Strokes Heart failure Arterial aneurysm Arsenic Toxicity
Hyperkeratosis Hypertension: Strokes Heart failure Arterial aneurysm Cancer: Skin cancer Lung cancer Kidney cancer Bladder cancer Arsenic Toxicity
Arsenic Pollution • Herbicide • Insecticide • Pesticide
Arsenic Pollution • Herbicide • Insecticide • Pesticide • Brain damage has been found in those working the sprayers
Arsenic Pollution • Herbicide • Insecticide • Pesticide • Brain damage has been found in those working the sprayers • Kingicide
Arsenic Pollution • Herbicide • Insecticide • Pesticide • Brain damage has been found in those working the sprayers • Kingicide • King George III of Great Britain • Francesco I de' Medici, Grand Duke of Tuscany
Arsenic Pollution • Chromated copper arsenate (CCA) (Tanalith brand)
Arsenic Pollution • Chromated copper arsenate (CCA) (Tanalith brand) • Protects wood from various forms of decay • The arsenic acts as an insecticide
Arsenic Pollution • Chromated copper arsenate (CCA) (Tanalith brand) • Protects wood from various forms of decay • The arsenic acts as an insecticide • Depending on application and environment, the amount of chemical leaching varies
Arsenic Pollution • Arsenic is a waste product of some mining and smelting activities • Coal, gold, etc. • Poor handing leads to various forms of pollution, including arsenic in groundwater
Arsenic Pollution • Arsenic is found in various geological formations • Granites containing cooper and tin
Arsenic Pollution • Arsenic is found in various geological formations • Granites containing cooper and tin • Natural wearing can lead to its release
Arsenic Pollution • Arsenic is found in various geological formations • Granites containing cooper and tin • Natural wearing can lead to its release • Wells may tap into polluted ground water • Wells are commonly used as a source of microbiologically safe drinking water without much though to possible chemical dangers
Arsenic PollutionWorldwide Source: World Bank
Arsenic PollutionUnited States • For decades the regulatory limit for arsenic was set to 50 g/L (ppb)
Arsenic PollutionUnited States • For decades the regulatory limit for arsenic was set to 50 g/L (ppb) • Recently the U.S. Environmental Protection Agency lowered the limit to only 10 g/L (ppb)
Arsenic PollutionUnited States • For decades the regulatory limit for arsenic was set to 50 g/L (ppb) • Recently the U.S. Environmental Protection Agency lowered the limit to only 10 g/L (ppb) • Many sites which previously had “safe” levels of arsenic are now over the limit by as much as five times
Cleanup • An inexpensive and efficient method for arsenic remediation is needed
Cleanup • An inexpensive and efficient method for arsenic remediation is needed • Most existing methods are impractical
Cleanup • An inexpensive and efficient method for arsenic remediation is needed • Most existing methods are impractical • They lack specificity • Are small scale • Require alteration of water chemistry • Fail to remove trace quantities • Or are completely ineffective against As(III) which is uncharged at natural pH
Yeast • Yeast has defense mechanisms to protect itself from heavy metals and metalloids
Yeast • Yeast has defense mechanisms to protect itself from heavy metals and metalloids • As(III) • Transported back out of the yeast cells • Bound by glutathione and stored in vacuoles • Bound by phytochelatins and sulfides forming various complexes
Yeast • Yeast has defense mechanisms to protect itself from heavy metals and metalloids • As(III) • Transported back out of the yeast cells • Bound by glutathione and stored in vacuoles • Bound by phytochelatins and sulfides forming various complexes • As(V) • Reduced to As(III) and dealt with accordingly
Cysteine • As(III) has an affinity for thiol groups
Cysteine • As(III) has an affinity for thiol groups • This is why it binds to proteins, wreaking havoc on various organisms
Cysteine • As(III) has an affinity for thiol groups • This is why it binds to proteins, wreaking havoc on various organisms • This is also how it binds to PC and is made harmless within the Yeast
Bioremediation • Efficiency must be increased
Bioremediation • Efficiency must be increased • Saccharomyces cerevisiae 15616 Acr3Δ
Bioremediation • Efficiency must be increased • Saccharomyces cerevisiae 15616 Acr3Δ • The Acr3p membrane transporter is deleted • As(III) is prevented from reentering the water
Bioremediation • Efficiency must be increased • Saccharomyces cerevisiae 15616 Acr3Δ • The Acr3p membrane transporter is deleted • As(III) is prevented from reentering the water • Arabidopsis thaliana phytochelatin synthase
Bioremediation • Efficiency must be increased • Saccharomyces cerevisiae 15616 Acr3Δ • The Acr3p membrane transporter is deleted • As(III) is prevented from reentering the water • Arabidopsis thaliana phytochelatin synthase • Increase the quantity of available PCs for binding As(III)
Bioremediation • Treponema denticola cysteine desulfhydrase
Bioremediation • Treponema denticola cysteine desulfhydrase • Available cysteine are stripped of their thiol groups, increasing the availability of free sulfides for binding As(III)
