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Designer Yeast for Low-Cost Arsenic Removal

Shailendra Singh1, Wonkyu Lee2, Dhawal Shah3, Nancy A. Da Silva3, and Wilfred Chen4. (1) Chemical & Environmental Engineeing, Cell Molecular & Developmental Biology, University of California, Riverside, Bourns Hall A 242, Riverside, CA 92521, (2) Chemical & Environmental Engineering, University of California, Riverside, Bourns Hall A 242, Riverside, CA 92521, (3) Chemical Engineering and Materials Science, University of California, Irvine, ET 936 The Henry Samueli School of Engineering, University of California, Irvine, Irvine, CA 92697, (4) Chemical and Environmental Engineering, University of California, Riverside, Bourns Hall A 242, Riverside, CA 92521

Arsenic (As) is an extremely toxic metalloid pollutant affecting health of millions of people worldwide. Arsenic exposure has been associated with many major health disorders such as increased risk of hypertension, skin, lung and bladder cancer. EPA's new regulatory limit on arsenic has been set at 10 ppb which would require corrective actions for almost 4000 water supply systems serving 20 million people across the country. In this work we report metabolic engineering on yeast Saccharomyces cerevisiae by combining its naturally existing As detoxification pathways with defense mechanisms used by other organism for the development of a designer biosorbent with an increased affinity to accumulate As. Expression of the Arabidopsis thaliana phytochelatin synthase gene (atPCS) resulted in production of arsenic binding phytochelatins (PC) and led to a 3-fold increase in As accumulation. Furthermore overexpression of the genes responsible for the uptake of arsenite (FPS1) and arsenate (PHO84) increased the amount of As being transported into the cell 2.5-fold and 2.6-fold, respectively. Resting engineered cells were able to reduce trace amounts (50 ppb) of arsenic below 10 ppb very rapidly. These results along with experiments on internal sequestration of As using a bacterial arsenite-binding peptide arsR will be reported. Currently, our focus is to combine the transport and sequestration system for further improved arsenic accumulation and removal.


Web Page: www.engr.ucr.edu/~wilfred/