Genetic engineering of E.coli to biofuels

Genetic engineering of E.coli to biofuels

Biofuels and crucial chemicals have been produced from genetically engineering strains of ECOLI through fatty acids synthase deregulation in the microorganism. The deregulation makes the organism to produce useful chemicals. Lubricants, detergents, and the potential use of methyl ketones as potential fuels are some of the known benefits of the products. In earlier studies, scholars carried studies that were based on highly regulated enzymatic processes. Still, recombinant technology has been pivotal in enabling scientists to beat the initial limitation production associated with E.coli. The technology has enabled e development of an alternative fatty acids synthase system where enzymes from other microbes work with the original Fatty Acid Synthase from E.coli to boost the chemical producing capacity.

Bioethanol is one product that the bioengineers can produce from E.coli. Despite the low energy and high corrosiveness associated with ethanol. Production of ethanol for a long time has been through fermentation that uses S.cerevisae and Zymomonas mobilis in the process. The microbes were punctuated with the inability to ferment hexose sugars and pentose sugars, limiting the maximum ethanol yield from the conational fermentation. As a result of these shortcomings, Clostridium species and E.coli are used because they can ferment hexose and pentose sugars.  

The process where the native E.coli produces ethanol is endogenous, where under anaerobic state, one mole of glucose gets metabolized to two moles of format and later resulting oxidized to generate two moles of acetate and single mole ethanol.  In the endogenous process of production, the first step of glycoses is similar. The last step involves the reduction of acetyl-CoA to generate ethanol using AdhE. This natural process results in 1 mole of ethanol and two moles of acetate causing suboptimal ethanol production.

As mentioned, one significant challenge associated with the endogenous production of ethanol is suboptimal production. Bioengineers have genetically modified E.coli through the insertion of PDC and adhB genes associated with Z.mobilis. The genes are related to the expression of ethanol production. The adjustment makes it possible to use the different pathways producing 95% ethanol with no redox imbalance. Some researcher has developed, for example, E.coli ATCC 11303 strain through chromosomal integration techniques.  Succinic add production is another challenge that researchers have found when using genetically engineered E.coli to produce ethanol. The problem can be sorted through gene deletion. Gene frd encodes for the production of fumarate reductase that is known to provide that said acid.  The elimination of the gene resulted in a 95% decrease in acid production and resulted in higher ethanol production. The glucose utilization in E.coli for a long time disadvantaged the bioengineers when striving to produce ethanol from mixed sugars in lignocellulose hydrolysates. Over the years, the engineers have developed genetically engineered E.coli to utilize other sugars like xylose and other sugars with no ability to use glucose, making the process more efficient. In the anaerobic step of production, switching off glucose usage resulted in the conversion of glucose as well as other sugars to ethanol.

Gas stripping and pervaporation are known techniques that use ethanol fermentation broth.  Nitrogen or carbon dioxide used to remove the ethanol by sparging through the broth at a high rate. Pervaporation involves filtration, where the microbial cells are taken back to the production chamber while the rest of the contents are pervaporized to produce ethanol. Sugar utilization was found to increase when gas stripping was used as a means of expelling the ethanol. Ethanol and butanol production was also thought to be boosted with the application of the gas stripping and pervaporation.

References

Balan, V. (2014). Current Challenges in Commercially Producing Biofuels from Lignocellulosic Biomass. ISRN Biotechnology, 2014, 1-31. https://doi.org/10.1155/2014/463074

Department of Energy, Office of Science. (2016, July 7). Engineering E. coli for biofuel, bioproduct production. ScienceDaily. Retrieved March 19, 2020, from www.sciencedaily.com/releases/2016/07/160707120503.htm

Koppolu, V., & Vasigala, V. K. (2016). Role of Escherichia coli in Biofuel Production. Microbiology insights, 9, 29–35. https://doi.org/10.4137/MBI.S10878

Sun, J., Tian, K., Wang, J., Dong, Z., Liu, X., & Permaul, K. et al. (2018). Improved ethanol productivity from lignocellulosic hydrolysates by Escherichia coli with regulated glucose utilization. Microbial Cell Factories, 17(1). https://doi.org/10.1186/s12934-018-0915-x