Team:UCL/Science/Bioprocessing

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Stages of large scale fermentation of E. coli:</p>
Stages of large scale fermentation of E. coli:</p>
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<a href="https://2014.igem.org/Team:UCL/Project/Manufacturing"><p>Check out our Manufacturing page where we outline how we are going to use Bioprocess Engineering to industrialize our remediation process.</p></a>
<a href="https://2014.igem.org/Team:UCL/Project/Manufacturing"><p>Check out our Manufacturing page where we outline how we are going to use Bioprocess Engineering to industrialize our remediation process.</p></a>
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Revision as of 20:47, 23 September 2014

Goodbye Azodye UCL iGEM 2014

Bioprocess Engineering

Overview

In the textile industry today, the global production of dyestuff amounts to over millions of tonnes per year. Azodyes represent two thirds of this value, a majority of which find their way to wastewater effluent streams. Characterised by the presence of one or more azo group (more on chemistry), this type of organic colorant is also found in cosmetics, pharmaceuticals and food industries. While the desirable properties of azodyes i.e. chemical stability, high molar extinction coefficient and fastness make them a dye-class of choice, their widespread use in countries such as India and China make them a dye to die for—literally. This is because, in parallel to being aesthetically intrusive to ecosystems, azodye breakdown products have been found to be mutagenic and carcinogenic. With such a high worldwide consumption, the benefits in developing and integrating a sustainable strategy for dealing with such effluent streams is clear. It is worth to note that the ‘azodye problem’ is exacerbated by the high costs, both financial (economic) and environmental, of current physiochemical and biological methods of treatment (more on current treatment). This year, we are looking into the processing options, novel and old, that are relevant to tackling the problem of azodye discharges. In order to assess the feasibility and determine key engineering parameters for each option, the most important dyestuff sector will be used as a case study: textiles and dyeing industry.

How is bioprocess engineering relevant?

Bioprocess engineering is a conglomerate of fields and is extensively employed to optimize a variety of production processes. In order to cope with market forces, industries for example the pharmaceutical, have had to considerably improve their bioprocessing tools and techniques. As a result a range of novel process alternatives have been developed to harness product-specific properties, each bearing benefits, disadvantages and costs. While these can be used to drive financial returns, biological processing is becoming a gateway to eco-friendly alternatives for the treatment of recalcitrant wastewater such as industrial effluents.

Why invest?





The design of a successful bioprocess requires careful analysis of the many factors that impact choice of design parameters and process variables. It is crucial to consider the cost of the process at each stage to assess it's large scale feasibility. For the problem at hand, the following interplay will affect an industry's choice to adopt a novel process:
A typical bioprocess involves the fermentation of a stock culture (e.g. E. coli) at a small scale which is subsequently scaled up to suitable production capacities. The products from the fermentative stages are then separated using a variety of techniques designed to exploit the orthogonal properties of desired products.
Stages of large scale fermentation of E. coli:


Check out our Manufacturing page where we outline how we are going to use Bioprocess Engineering to industrialize our remediation process.




The design of a process

with azodyes
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The contamination of natural habitats surrounding textile factories by coloured (azodye-rich) effluents is a real problem (more). This is because the enzymatic breakdown products of azodyes i.e. aromatic amines, are carcinogenic when ingested. These can not only build up within local ecosystems but can also be a hazard to humans through bio-accumulation in the food chain. With a large section of dyehouse effluents consisting of dyes that have half-lives spanning over decades, the latter remain in the environment for long periods of time.

Understanding the issues

with current methods
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With regards to current technologies in the textile industry, exorbitant volumes of water are used for processing (around 90%), the rest being used for heat exchange purposes. Unfortunately most of the water used for processing is discharged as waste, resulting in highly diluted azodye effluent streams. Secondly, the recalcitrant nature of azodyes hikes the inherent costs of large-scale physical separation systems. As a result, industrial processes used to deal with such soluble hazardous wastes would not be a feasible option to deal with azodye effluents.

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By using whole cell biocatalysis as the workhorse for detoxification, this process will yield lucrative byproducts such as quinones, that can then be separated from the process stream and sold off.

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And then there was


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Looking into the process

Key Features of Our System
  • -Fermentation stage is where optimized growth will take place by controlling mixing and oxygen supply. At the end of this stage, viable E. coli cells expressing the enzymes of interest will be present in a broth.
  • -Module- see cross section of a single system. Continuous flow system with flow rates and residence times based on mass transfer kinetics, specific to E. Coli.
  • -Module 1 designed to capture the bulk of the azodyes, module 2 is a polishing step.
  • -Both anaerobic and aerobic reactions take place at the same time in both the modules, design based on gas supply (nitrogen vs. oxygen).
  • -Cleaning operation using biodegradable chemical at high flow rate (from holding tank 2).
  • -Continuous recycle system for maximal active and diffusive uptake.
  • -Filter modules- exploring the use of disposable low cost agricultural waste for filtration.
  • -Further processing- based on the commercial value of the breakdown products, investments could be made into higher-tier technology such as chromatography columns to separate the breakdown products individually.

Microbial Fermentation (Stage 1)



Small-scale bioreactors are often the workhorse during process development. By experimenting at this scale, it is possible to determine the optimum growth conditions for E. coli. This will allow to assess costs at the required scale based on biomass requirements.We are using E. coli to cultivate the enzymes necessary for the biodegradation of azo dyes (azo reductase, laccase). By combining information on the production of azo dyes in textile factories and stoichiometric relations, we will design an optimised cell growth (fermentation) stage.








Module operation (Stage 2)

After the fermentation stage, the E. coli biomass is dispersed in a liquor also containing various byproducts. A concentration step could be beneficial to reduce volumes in the next stage. However, capital costs of such unit operations would not be attractive to potential dyeing companies deciding to acquire the entire system. The subsequent modules (MOD) are equipped to handle large volumes and operate in continuous-flow mode with intermittent discharges. By controlling residence time and operating flow rates, it will be possible to achieve a cell recovery deemed efficient. These will be then immobilized onto the surface of the plates within the modules. There exists a wide range of immobilization strategies used for biological wastewater treatment and this is what gives the unit its modular character. By supporting a number of immobilization methods without changing the hardware, MOD allows for the enzymatic breakdown of a wide range of recalcitrant chemicals that might be financially and environmentally costly to treat using conventional methods. (more to come)

Major components of treatment process

Contact Us

University College London
Gower Street - London
WC1E 6BT
Biochemical Engineering Department
Phone: +44 (0)20 7679 2000
Email: ucligem2014@gmail.com

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