A Novel Bioreactor for High Density Cultivation of Diverse Microbial Communities
December 25th, 2015
A novel reactor design, coined a high density bioreactor (HDBR), is presented for the cultivation and study of high density microbial communities. Here, the HDBR is successfully applied in a photobioreactor (PBR) configuration for the study of nitrogen metabolism by a mixed high density algal community.
The overall goal of this bioreactor design and experiment is to demonstrate the cultivation of a highly dense, mixed photosynthetic community in a novel bioreactor for effective treatment of wastewater. This method can be used to answer key questions such as how to design and operate algal bioreactors in order to remediate waste streams, as well as how to cultivate algal biomass. The main advantage of this technique is the cultivation of high density algal biomass in the absence of external separation methods.
We first had the idea for this application when we realized that this high density bioreactor system was highly successful in growing heterotrophic bacteria from activated sludge in the treatment of organic compounds from wastewater, as well as autotroph nitro fires and de nitro fires in the treatment of the nitrogenous wastewater contaminant ammonia. Demonstrating this procedure is Thomas Thompson, A-B-S-M-S student at Drexel University, who's also a co-op and technician in my laboratory. To begin place the reactor on a mixing plate and add a stir bar to the reactor.
Place the recycle tank beside the stir plate and reactor so that the effluent port of the tank is directed towards the edge of the lab bench. Place the waste container underneath the effluent port of the recycle tank. Then place the feed tank next to the recycle tank.
Secure the reactor against tipping with an appropriately sized stand and clamp. Insert neoprene peristaltic pump tubing in the recycle pump and feed pump heads. Install the pump heads onto the pump drives with the screws provided with the pump drives.
Next connect pump a's tubing to the ports on the reactor and the recycle tank. Insert the end of pump B'S tubing into the feed tank and the recycle tank. Connect the top reactor port to the recycle tank with tubing.
Finally, apply clamps to the tubing at the reactor ports. Prepare five liters of in fluent or feed solution to start the reactor. First, add 0.5 milliliters of mineral solution per liter of solution being made.
Then dilute two milliliters of ammonia stock solution, and two milliliters of nitrate stock solution to one liter total volume. Add 750 milliliters of the feed solution to the reactor. Fill the recycle tank with 500 milliliters of feed solution.
Use a long pipette to gently add an inoculate suspension containing 1.5 grams of algae near the bottom of the reactor. Allow the inoculum to settle to the bottom of the reactor as insured by visual observation before proceeding to the next step. Place the aeration stone in the recycle tank and turn it on.
Once the cells have settled, remove the tube clamps and turn on pump A to a slow flow rate. Using the controls on the pump drive unit, gradually add the feed solution to the recycle tank as the solution is pumped into the reactor. Continue the addition until both the reactor and the recycle tank are at capacity and effluent.
Starts to exit the recycle tank via the top port. Pour the remaining feed solution into the feed tank. Then set pump a to 19 revolutions per minute, establishing a recycle flow rate of 72.5 milliliters per minute.
Observe the algae begin to loft from the bottom of the reactor using the gradations on the reactor. Determine the algae biomass zone height. Ensure that the height is constant before proceeding to the next step.
When setting the speed of the mixing plate, it is vital to monitor the height and stability of the algal biomass to prevent the loss of biomass. Modern incremental changes to the speed of the mixing bar help to prevent this from occurring. Turn on the mixing plate at very low speed.
A setting of one or two is appropriate to start. The mixing bar will assist in lofting biomass further, but aggressive mixing will cause algae. To leave the reactor, enter the recycle tank and leave in the effluent.
Start the feed pump. After observing a clear boundary between the algal plug and the reactor fluid, set the pump to 25 revolutions per minute, establishing a flow rate of 1.5 milliliters per minute. Observe the reactor fluid, exit the effluent port due to gravity and displacement caused by the incoming influenced stream.
Carry out sample collection activities prior to performing maintenance on the reactor system. Collect 20 milliliters of effluent and influence samples daily. Collect effluent samples from within the recycle tank.
Collect influence samples directly from the feed tank.Vacuum. Filter the samples to remove suspended solids prior to storage and analysis. Store the fluent and effluent samples at minus 20 degrees Celsius until further analysis.
Limit the number of freeze thaw cycles. The samples are subjected to finally carry out sample analysis for nitrate nitrite and ammonia using standard techniques. Ammonia removal was observed over all ranges of feet composition, but the magnitude of ammonia removal was not significantly affected by the influence ammonia composition.
Similarly, ammonia removal not significantly affected by the influence nitrate composition nitrate was observed to accumulate within the reactor through most of the influe compositions. Nitrate removal was negatively related with ammonia feed composition, whereas removal of nitrate was positively related with nitrate feed composition. The removal of ammonia coinciding with the creation of nitrate suggests that ammonia and nitrate oxidizing bacteria are present within the mixed community and that these organisms are contributing to nitrogen species transformation within the reactor.
The oxygen required by ammonia and nitrite oxidizing bacteria would be provided by aeration within the recycle tank and transported through the biomass zone within the reactor via the recycle pump. In addition to chemical composition of in fluent and effluent monitoring, the suspended solids content within the reactor has been found to be a good predictor of population crashes. Large and sudden changes in feed composition can have adverse effects on the microbial community and may result in reactor crashes.
Consequently, feed composition schedules should be carefully selected to prevent such crashes, should So.Although this method can provide insight into the algal bacterial systems that function in this photo bioc, we can also study heterotrophic bacteria from activated sludge in the system as well as nitro fires and de nitro fires, ox bacteria and phosphate cating organisms Once mastered a high density bioreactor can be assembled and seated in under two hours daily. Activities such as sample collection and ilu preparation should take about an hour. We hope that this demonstration encourages other investigators to adopt this reactor in order to study other microbial systems.
Thank you for watching and good luck with your experiments.
View the full transcript and gain access to thousands of scientific videos
Overview
This article presents a novel high density bioreactor (HDBR) designed for cultivating high density microbial communities. The HDBR is utilized in a photobioreactor configuration to study nitrogen metabolism in a mixed algal community.
Key Study Components
Area of Science
- Microbial ecology
- Biotechnology
- Wastewater treatment
Background
- The HDBR allows for the cultivation of dense algal biomass.
- This method eliminates the need for external separation techniques.
- It has previously shown success in growing heterotrophic bacteria from wastewater.
- The system is effective in treating nitrogenous contaminants like ammonia.
Purpose of Study
- To demonstrate the cultivation of a mixed photosynthetic community.
- To explore the design and operation of algal bioreactors.
- To investigate the remediation of waste streams using algal biomass.
Methods Used
- Placement of the reactor on a mixing plate.
- Addition of a stir bar to facilitate mixing.
- Application of the HDBR in a photobioreactor setup.
- Monitoring nitrogen metabolism in algal communities.
Main Results
- The HDBR successfully cultivated high density algal communities.
- Effective treatment of nitrogenous wastewater was demonstrated.
- The system showed potential for large-scale algal biomass production.
- Key operational parameters for algal bioreactors were identified.
Conclusions
- The HDBR is a promising tool for wastewater treatment.
- It facilitates the growth of mixed algal communities without external separation.
- This approach can enhance the efficiency of algal biomass cultivation.
Frequently Asked Questions
Executive Industry Relevance
High density bioreactor (HDBR) technology enables the cultivation and study of diverse microbial communities at scale, supporting robust evaluation of nitrogen metabolism and biomass productivity. This platform eliminates external separation steps, streamlining workflows for wastewater bioremediation and microbial system interrogation. Its reproducible, high-density cultivation environment enhances predictive confidence for early-stage bioprocess development and microbial target validation.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables controlled hypothesis testing of microbial community function and nitrogen transformation.
- Supports mechanistic de-risking by isolating the impact of feed composition on nitrogen removal.
- Facilitates functional validation of ammonia- and nitrite-oxidizing bacteria within mixed communities.
Screening & Assay Development
- Provides a standardized platform for reproducible cultivation of high-density microbial and algal systems.
- Delivers quantitative outputs on nitrogen species removal, supporting assay comparability.
- Reduces variability by maintaining a stable biomass zone and low suspended solids in effluent.
Translational & Preclinical Research
- Enables study of microbial community resilience and response to feed composition changes, informing translational bioprocess design.
- Supports continuity from discovery to scale-up by modeling operational stability and crash predictors.
- Aligns with risk-adjusted advancement decisions through quantitative monitoring of system performance.
Pipeline & Workflow Integration
The HDBR platform integrates from early discovery of microbial function through assay development and preclinical bioprocess modeling, supporting iterative optimization and translational continuity.
- Discovery Biology: Facilitates hypothesis-driven testing of nitrogen metabolism and microbial interactions.
- Screening: Provides reproducible, quantitative readouts for nitrogen removal and biomass stability.
- Analytics: Enables daily measurement of influent and effluent nitrogen species for comparative analysis.
- Translational Research: Models operational stability and crash risk under variable feed conditions.
- Enterprise Reuse: Adaptable for diverse microbial systems, supporting broad R&D portfolio needs.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in microbial system performance and target validation.
- Operational Value: Streamlines workflows by eliminating external separation and enabling rapid setup.
- Strategic Value: Supports data-driven go/no-go decisions and reduces late-stage process risk.
- Portfolio Impact: Enhances risk-adjusted prioritization for microbial bioprocess development.
Implementation Considerations
- Requires expertise in microbial cultivation and reactor operation.
- Needs access to analytical infrastructure for nitrogen species quantification.
- Demands cross-team standardization of feed composition and sampling protocols.
- Adaptable to various microbial and algal systems with protocol adjustments.
- Feed composition changes must be managed to prevent population crashes.
