Team:NPU-China
Abstract
Acrylic acid is a bulk chemical raw material, which is widely used in many fields because of its excellent
polymerization capacity, such as paint, glue, and even mobile phone screen protective film. The average
annual market demand of acrylic acid is up to 8 million tons, and the market value is nearly 10 billion
US dollars, which shows a promising market prospect. At present, acrylic acid is made from propylene (which
is obtained by petroleum cracking) after multi-step treatment, resulting in environmental pollution,
high energy consumption and a lack of sustainablility.
This year, we aim to use a greener and more environmentally-
friendly carbon source, glycerol, to achieve all green production of acrylic acid. Compared to traditional
chemical synthesis methods, Synbio is relatively greener and more sustainable. Also, glycerol costs less than propene.
We constructed our cell factory based on 4 levels, which are—
Core Part
We use ceaS2 enzyme as the core part, but acrylic acid is a by-product of ceaS2 enzyme, whose catalytic effect of wild type
is very weak with acrylic acid production only 1mg/L. Hence, we hope to improve the catalytic
effect of ceaS2 enzyme.
We designed ceaS2 enzyme mutants via the AEMD(Auto Enzyme Mutation Design)
platform and screened for ceaS2 mutants that own better acrylic acid yield by HPLC(High Performance Liquid Chromatography)
and HTS(High throughput screening).
System
Respectively, E. coli and S. cerevisiae are the two sorts of model organisms that are most convenient to operate in the prokaryote and eukaryote. Therefore, in terms of our choice of the chassis organisms, we have E. coli MG1655 and S. cerevisiae BY4741 tested individually.
Pathway
We need to design two different metabolic pathways for two different chassis organisms and propose different
optimization schemes. We introduced the ceaS2 enzyme exogenously on the basis of the glycerol
metabolism of the two organisms, so that they could produce the target product acrylic acid using the
intermediates G3P and DHAP.
Besides the construction of the pathways, we also reconstructed
and optimized the original metabolic pathway to increase the carbon flux rate of the designed pathway
and reduced the loss of by-pass carbon flux.
Production
All of the previous processes were applied in building the engineered microorganism strains which have a high production of acrylic
acid. In the subsequent fermentation, we also determined the best conditions
of the engineered microorganism strains.
Therefore, we selected to control the carbon source, buffer, temperature, pH
and other conditions to optimize the cell production process.
