Application Summary
POC-5-dinsdale-C1net-public-summary
In-situ Multiphase Compartmentalised Substrate Shuttle Bioreactor for Protein and Platform
Chemicals
PI Richard Dinsdale, University of South Wales
Traditional microbial biotechnology processes can produce a wide range of suitable products
ranging from foodstuffs such as lipids and proteins, pharmaceuticals, platform chemicals and biomaterials such as bioplastics. However, these products are dependent on high grade
carbon and energy substrates such as molasses which can be used for human food
consumption. To prevent the competition with food supply and possibly supplement
traditional food sources, it is possible that hydrogen from renewable energy production could
be used in these processes. However there are substantial explosion risks in using hydrogen
in aerobic processes. The project here presents a novel bioreactor design the substrate
shuttle bioreactor which would enable these aerobic processes to utilize hydrogen as an
energy substrate. This hydrogen could be provided by renewable energy sources such as
wind power and provide an alternative market to the traditional electrical supply sector.
Report Summary
POC-5-dinsdale-C1net-public-summary-report
In-situ Multiphase Compartmentalised Substrate Shuttle Bioreactor for Protein and Platform
Chemicals
PI Richard Dinsdale, University of South Wales
A wide range of useful chemicals and products are produced by microorganisms, however
these process use feedstocks which could be used as food. There is significant interest in
the utilization of bacterial processes for the production of “green” or sustainable chemicals
which are not dependent on feedstocks which compete with the production of food. One
promising avenue is to use hydrogen and carbon dioxide based microbial metabolisms, often
called C1 metabolism, as this route would be independent of the traditional energy and
carbon supplying substrates such as molasses which could be used a human foodstuff.
Hydrogen can be produced electrolytically from renewable energy sources which have
variable and intermittent energy output such as wind power and thus could be used in areas
where wind output is grid constrained for electricity production. A number of hydrogen and
carbon dioxide related metabolic pathways have significant challenges to due to either
feedstock incompatibilities or feedstock /product inhibition which hinder either the industrial exploitation due to explosion risks at larger scales or low product/ feedstock concentration which increases the cost of product recovery.
One commonly proposed microbial route is the use of hydrogen oxidizing microorganisms
such as Cuprovidius necator to produce products such as proteins or bioplastics. However
as indicated with the original name of “Knallgas” or “bang gas “ for this metabolic pathway,
the scale up of this particular process faces significant challenges due to the flammability of
hydrogen and oxygen. The flammability of hydrogen is particular problem as this extends
over a very wide range (4-75% H2 in air) and has a low ignition energy for combustion, 10%
of that required by petrol. Therefore to reduce the risk of explosion, the reactor will need
either to be operated under low concentration of either substrate or oxygen. However this
approach would probably result in reduced process productivity as the microorganisms
would always be under either low substrate or oxygen availability. In this project, the
substrate shuttle reactor concept uses a novel configuration of a membrane separated
bioreactor design to overcome these challenges.
Another C1 metabolic route that could be exploited for “green” chemical platform chemicals
the production of volatile fatty acids such as acetic acid from hydrogen and carbon dioxide
using bacteria such as Clostridium aceticum. This process would have reduced flammability
issues but would face challenges due to the relative low product concentrations and the
decrease in-reactor pH due to the production of an acid product. To increase productivity
and reduce the addition of alkali then the continual removal of product e.g. via membrane
extraction would offer significant advantages. As there are a number of aerobic microorganisms that can be used for the production of lipids, single cell protein, and
bioplastics which use acetic acid and thus if these metabolisms were coupled with anaerobic
acetic acid production from hydrogen, a safe process could be implemented. It could be
potentially possible to produce a range of foodstuffs, oils and single cell protein which would
be independent of the traditional food production systems.