Fabrication of Bacteria Environment Cubes with Dry Lift-Off Fabrication Process for Enhanced Nitrification

PLOS ONE, Dec 2019

We have developed a 3D dry lift-off process to localize multiple types of nitrifying bacteria in polyethylene glycol diacrylate (PEGDA) cubes for enhanced nitrification, a two-step biological process that converts ammonium to nitrite and then to nitrate. Ammonia-oxidizing bacteria (AOB) is responsible for converting ammonia into nitrite, and nitrite-oxidizing bacteria (NOB) is responsible for converting nitrite to nitrate. Successful nitrification is often challenging to accomplish, in part because AOB and NOB are slow growers and highly susceptible to many organic and inorganic chemicals in wastewater. Most importantly, the transportation of chemicals among scattered bacteria is extremely inefficient and can be problematic. For example, nitrite, produced from ammonia oxidation, is toxic to AOB and can lead to the failure of nitrification. To address these challenges, we closely localize AOB and NOB in PEGDA cubes as microenvironment modules to promote synergetic interactions. The AOB is first localized in the vicinity of the surface of the PEGDA cubes that enable AOB to efficiently uptake ammonia from a liquid medium and convert it into nitrite. The produced nitrite is then efficiently transported to the NOB localized at the center of the PEGDA particle and converted into non-toxic nitrate. Additionally, the nanoscale PEGDA fibrous structures offer a protective environment for these strains, defending them from sudden toxic chemical shocks and immobilize in cubes. This engineered microenvironment cube significantly enhances nitrification and improves the overall ammonia removal rate per single AOB cell. This approach—encapsulation of multiple strains at close range in cube in order to control their interactions—not only offers a new strategy for enhancing nitrification, but also can be adapted to improve the production of fermentation products and biofuel, because microbial processes require synergetic reactions among multiple species.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0165839&type=printable

Fabrication of Bacteria Environment Cubes with Dry Lift-Off Fabrication Process for Enhanced Nitrification

November Fabrication of Bacteria Environment Cubes with Dry Lift-Off Fabrication Process for Enhanced Nitrification S. A. P. L. Samarasinghe 0 1 2 Yiru Shao 0 2 Po-Jung Huang 0 2 Michael Pishko 0 2 Kung-Hui Chu 0 2 Jun Kameoka 0 1 2 0 a Current address: Wisenbaker Engineering Building , 3128 TAMU, 188 Bizzell Street , College Station , Texas, 77843 , United States of America ¤b Current address: CE Office Building, 3136 TAMU, 199 Spence St , College Station , Texas, 77843 , United States of America ¤c Current address: Reed-McDonald Bldg , 575 Ross St , College Station , TX, 77840 , United States of America ¤d Current address: Emerging Technologies Building, 3120 TAMU, 101 Bizzell Street , College Station , TX, 77843 , United States of America 1 Department of Electrical & Computer Engineering, Texas A&M University, College Station, Texas, United States of America, 2 Zachry Department of Civil Engineering, Texas A&M University, College Station, Texas, United States of America, 3 Department of Material Science and Engineering, Texas A&M University, College Station, Texas, United States of America, 4 Department of Biomedical Engineering, Texas A&M University, College Station , Texas , United States of America 2 Editor: Pankaj Kumar Arora, MJP Rohilkhand University , INDIA We have developed a 3D dry lift-off process to localize multiple types of nitrifying bacteria in polyethylene glycol diacrylate (PEGDA) cubes for enhanced nitrification, a two-step biological process that converts ammonium to nitrite and then to nitrate. Ammonia-oxidizing bacteria (AOB) is responsible for converting ammonia into nitrite, and nitrite-oxidizing bacteria (NOB) is responsible for converting nitrite to nitrate. Successful nitrification is often challenging to accomplish, in part because AOB and NOB are slow growers and highly susceptible to many organic and inorganic chemicals in wastewater. Most importantly, the transportation of chemicals among scattered bacteria is extremely inefficient and can be problematic. For example, nitrite, produced from ammonia oxidation, is toxic to AOB and can lead to the failure of nitrification. To address these challenges, we closely localize AOB and NOB in PEGDA cubes as microenvironment modules to promote synergetic interactions. The AOB is first localized in the vicinity of the surface of the PEGDA cubes that enable AOB to efficiently uptake ammonia from a liquid medium and convert it into nitrite. The produced nitrite is then efficiently transported to the NOB localized at the center of the PEGDA particle and converted into non-toxic nitrate. Additionally, the nanoscale PEGDA fibrous structures offer a protective environment for these strains, defending them from sudden toxic chemical shocks and immobilize in cubes. This engineered microenvironment cube significantly enhances nitrification and improves the overall ammonia removal rate - OPEN ACCESS Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: The imaging work was partially supported by NIH-NCRR (1S10RR22532-01). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. per single AOB cell. This approachÐencapsulation of multiple strains at close range in cube in order to control their interactionsÐnot only offers a new strategy for enhancing nitrification, but also can be adapted to improve the production of fermentation products and biofuel, because microbial processes require synergetic reactions among multiple species. Introduction Cross-linked hydrogels such as polyethylene glycol (PEG) or collagen are important materials in the biological and medical fields [ 1–9 ]. The porous nanostructure of hydrogels is able to transport molecules and provide flexible but stable mechanical characteristics [10]. Recently, these hydrogels have been miniaturized to increase molecular transport in a microscale environment. Many of these microscale hydrogels are fabricated by conventional emulsion and polymerization techniques. However, it is challenging to create the uniform size distribution of hydrogels [ 11– 17 ]. To address this issue, photolithography [ 18 ], imprint lithography [ 19 ], and micro-molding [ 20–21 ] involving the patterning process for micro-scaling the polyethylene glycol diacrylate (PEGDA) have all been investigated for the roles they play in precise dimension control. The precise patterning of photo-curable hydrogels has significant advantages over conventional emulsification approaches. Multiple layered hydrogel microstructures are also fabricated by flow lithography [22]; however, the complicated control system leads to a low throughput of 3D hydrogel structures. The microfabrication technique for hydrogels also provides a method of encapsulating biological materials such as cells or bacteria. This (...truncated)


This is a preview of a remote PDF: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0165839&type=printable

S. A. P. L. Samarasinghe, Yiru Shao, Po-Jung Huang, Michael Pishko, Kung-Hui Chu, Jun Kameoka. Fabrication of Bacteria Environment Cubes with Dry Lift-Off Fabrication Process for Enhanced Nitrification, PLOS ONE, 2016, Volume 11, Issue 11, DOI: 10.1371/journal.pone.0165839