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
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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)