| CPU_Nanjing - iGEM 2022

Overview

In order to verify the technical feasibility of manufacturing phosphate from phosphite in the context of terrestrial planets, we developed our Hardware prototype, a solar-energy-driven sequence batch bioreactor. With phosphite as the raw material, we successfully performed phosphate production in bench-scale.

There are four major parts of our bioreactor (Figure 1): algae cultivation tank (section A), initial bacteria cultivation tank (section B), main fermentation tank (section C), solar energy conversion module (section D). The reaction flow is showed below:

Figure 1. Work flow of our solar-energy-driven sequence batch bioreactor

Components

Figure 2. Carbon dioxide generator

Carbon Dioxide Generator: It is designed to serve as a carbon dioxide source to simulate the atmosphere on terrestrial planets which may contain carbon dioxide. A steady flow of carbon dioxide gas enters section A, the algae cultivation tank, where it is converted into organic substances by algae consistent with oxygen release.

Figure 3. Container & Electric Heater

Container & Electric Heater: This component is designed to ‘cook’ the algae for our engineered E. coli. It is powered by the battery module, which is charged by the solar panel.

Figure 4. Solar panel

Solar Panel: It generates power from sunlight and charges the battery module. The latter will supply power for our electric heater.

Figure 5. Battery module

Battery Module: This is a UPS (Uninterruptible Power Supply) who accepts power input from the solar panel. It powers the electric heater directly so that the algae will be converted into lysate assimilable to our engineered E. coli.

Figure 6. Peristaltic pump

Peristaltic Pump: It’s a precise instrument used to transfer solution between different sections.

Integrated Hardware

Figure 7. Front view

Section A: Algae Cultivation Tank

This is the key part for algae cultivation and is connected to all other sections. Culture system is contained inside, whose function map is showed in Figures 9 and 10:

Figure 8. Function map 1 of section A

Figure 9. Function map 2 of section A

    Blue Arrow: Carbon Dioxide Input

    Green Arrow: Oxygen-Rich Gas Flow

    Yellow Arrow: Algae Transfer Direction

    Purple Arrow: Phosphate Input (Derived from phosphite oxidation by our engineered E. coli)

Section B: Initial Bacteria Cultivation Tank

Figure 10. Front view of section B

The initial inoculum is contained in this section and provide phosphate for algae to grow. Oxygen produced from photosynthesis by algae enters this section through a tube from section A (Marked as green arrow in Figure 9 and 10). Solution containing phosphate is transferred to section A through another tube (Marked as purple arrow in Figure 9 and 10).

Section C: Phosphate Production Tank

Figure 11. Side view of section C

Phosphate manufacture takes place in this section. Engineered E. coli consumes oxygen released from section A through a tube between them (Marked as green arrow in Figure 11). The algae lysate , together with the substrate (phosphite) waiting to be oxidized, is fed to the engineered E. coli. After aerobic cultivation, engineered E. coli rich in polyphosphate is concentrated by filter concentrate processing. The final product phosphate can then be recovered from the supernatant after anaerobic phosphate release process.

Section D: Solar Energy Conversion Module

Figure 12. Solar energy conversion module

This section provides energy to cook the algae for the engineered E. coli. It contains a solar panel, battery module, electric heater and algae container. The panel collects solar energy and stores it inside the battery module. The latter then powers electric heater directly.