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Guo F, McAuliffe JC, Bongiorni C, Latone JA, Pepsin MJ, Chow MS, Dhaliwal RS, Hoffmann KM, Brazil BT, Heng MH, Robinson SL, Wackett LP, Whited GM. A Procedure for Removal of Cyanuric Acid in Swimming Pools Using a Cell-Free Thermostable Cyanuric Acid Hydrolase. J Ind Microbiol Biotechnol 2021; 49:6426183. [PMID: 34788856 PMCID: PMC9118981 DOI: 10.1093/jimb/kuab084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 11/08/2021] [Indexed: 11/13/2022]
Abstract
Cyanuric acid (CYA) is used commercially for maintaining active chlorine to inactivate microbial and viral pathogens in swimming pools and hot tubs. Repeated CYA addition can cause a lack of available chlorine and adequate disinfection. Acceptable CYA levels can potentially be restored via cyanuric acid hydrolases (CAH), enzymes that hydrolyze CYA to biuret under mild conditions. Here we describe a previously unknown CAH enzyme from Pseudolabrys sp. Root1462 (CAH-PR), mined from public databases by bioinformatic analysis of potential CAH genes, which we show to be suitable in a cell-free form for industrial applications based upon favorable enzymatic and physical properties, combined with high-yield expression in aerobic cell culture. The kinetic parameters and modeled structure were similar to known CAH enzymes, but the new enzyme displayed a surprising thermal and storage stability. The new CAH enzyme was applied, following addition of inexpensive sodium sulfite, to hydrolyze CYA to biuret. At the desired endpoint, hypochlorite addition inactivated remaining enzyme and oxidized biuret to primarily dinitrogen and carbon dioxide gases. The mechanism of biuret oxidation with hypochlorite under conditions relevant to recreational pools is described.
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Affiliation(s)
- Feng Guo
- Nutrition & Biosciences, International Flavors and Fragrances Inc., Palo Alto, California, USA
| | - Joseph C McAuliffe
- Nutrition & Biosciences, International Flavors and Fragrances Inc., Palo Alto, California, USA
| | - Cristina Bongiorni
- Nutrition & Biosciences, International Flavors and Fragrances Inc., Palo Alto, California, USA
| | - Jacob A Latone
- Nutrition & Biosciences, International Flavors and Fragrances Inc., Palo Alto, California, USA
| | - Mike J Pepsin
- Nutrition & Biosciences, International Flavors and Fragrances Inc., Palo Alto, California, USA
| | - Marina S Chow
- Nutrition & Biosciences, International Flavors and Fragrances Inc., Palo Alto, California, USA
| | - Raj S Dhaliwal
- Nutrition & Biosciences, International Flavors and Fragrances Inc., Palo Alto, California, USA
| | - Katherine M Hoffmann
- Nutrition & Biosciences, International Flavors and Fragrances Inc., Palo Alto, California, USA
| | - Bill T Brazil
- Nutrition & Biosciences, International Flavors and Fragrances Inc., Palo Alto, California, USA
| | - Meng H Heng
- Nutrition & Biosciences, International Flavors and Fragrances Inc., Palo Alto, California, USA
| | - Serina L Robinson
- Department of Environmental Microbiology, Eawag: Swiss Federal Institute for Aquatic Science and Technology, Überlandstrasse 133, CH-8600, Dübendorf, Switzerland
| | - Lawrence P Wackett
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - Gregory M Whited
- Nutrition & Biosciences, International Flavors and Fragrances Inc., Palo Alto, California, USA
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Cyanuric Acid Biodegradation via Biuret: Physiology, Taxonomy, and Geospatial Distribution. Appl Environ Microbiol 2020; 86:AEM.01964-19. [PMID: 31676480 DOI: 10.1128/aem.01964-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 10/27/2019] [Indexed: 12/24/2022] Open
Abstract
Cyanuric acid is an industrial chemical produced during the biodegradation of s-triazine pesticides. The biodegradation of cyanuric acid has been elucidated using a single model system, Pseudomonas sp. strain ADP, in which cyanuric acid hydrolase (AtzD) opens the s-triazine ring and AtzEG deaminates the ring-opened product. A significant question remains as to whether the metabolic pathway found in Pseudomonas sp. ADP is the exception or the rule in bacterial genomes globally. Here, we show that most bacteria utilize a different pathway, metabolizing cyanuric acid via biuret. The new pathway was determined by reconstituting the pathway in vitro with purified enzymes and by mining more than 250,000 genomes and metagenomes. We isolated soil bacteria that grow on cyanuric acid as a sole nitrogen source and showed that the genome from a Herbaspirillum strain had a canonical cyanuric acid hydrolase gene but different flanking genes. The flanking gene trtB encoded an enzyme that we show catalyzed the decarboxylation of the cyanuric acid hydrolase product, carboxybiuret. The reaction generated biuret, a pathway intermediate further transformed by biuret hydrolase (BiuH). The prevalence of the newly defined pathway was determined by cooccurrence analysis of cyanuric acid hydrolase genes and flanking genes. Here, we show the biuret pathway was more than 1 order of magnitude more prevalent than the original Pseudomonas sp. ADP pathway. Mining a database of over 40,000 bacterial isolates with precise geospatial metadata showed that bacteria with concurrent cyanuric acid and biuret hydrolase genes were distributed throughout the United States.IMPORTANCE Cyanuric acid is produced naturally as a contaminant in urea fertilizer, and it is used as a chlorine stabilizer in swimming pools. Cyanuric acid-degrading bacteria are used commercially in removing cyanuric acid from pool water when it exceeds desired levels. The total volume of cyanuric acid produced annually exceeds 200 million kilograms, most of which enters the natural environment. In this context, it is important to have a global understanding of cyanuric acid biodegradation by microbial communities in natural and engineered systems. Current knowledge of cyanuric acid metabolism largely derives from studies on the enzymes from a single model organism, Pseudomonas sp. ADP. In this study, we obtained and studied new microbes and discovered a previously unknown cyanuric acid degradation pathway. The new pathway identified here was found to be much more prevalent than the pathway previously established for Pseudomonas sp. ADP. In addition, the types of environment, taxonomic prevalences, and geospatial distributions of the different cyanuric acid degradation pathways are described here.
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