Team:NJTech China/Description
Description
Background
Phenylethanol is an aromatic alcohol with pleasant rose flavor, which is widely used in
cosmetic, food, pharmaceutical and other industries owning to its mild, warm, and rose-honey
like odor[1]. Additionally, it can also be used as
the substrate for the synthesis of other flavors or pharmaceutical compounds, such as
2-phenylethylacetate and phenylacetaldehyde.
Currently, three methods were mainly used for phenylethanol production, namely physical
extraction, chemical synthesis and biological synthesis. Due to its long production cycle,
extremely low yield and high cost, physical extraction of phenylethanol from natural plants is
not suitable for large-scale industrial production[2]. Currently, most of the
phenylethanol in the market is synthesized by chemical
methods using cheap chemical raw materials of benzene or styrene, which are harmful to the human
health and environment. Additionally, chemically synthesized phenylethanol often contains other
by-products, which seriously affects the quality of the product.
With the increasing demand for natural ingredients, the large-scale production of natural
phenylethanol is urgently needed. Microorganisms have the characteristics of small size, rapid
reproduction, high absorption, fast transformation and strive adaptability. The products
produced by microorganisms are relatively pure and have the features of low cost, short cycle,
high efficiency and green environmental protection. Among them, Saccharomyces
cerevisiae has a
clear genetic background, mature genetic manipulation methods, and high-level biosafety. Studies
have shown that yeast cells possess the de novo synthetic pathway of phenylethanol, and
phenylalanine can also be directly converted to phenylethanol by amino acid decomposition
metabolic pathway[3]. However, the titer of phenylethanol is still low. To improve
the
biosynthesis of phenylethanol, phenylacetaldehyde synthase, a key enzyme in the phenethylamine
pathway of plants, was introduced into the S. cerevisiae. And the enzyme activity was
enhanced
through promoter engineering.
Yeast-Microalgae Consortia was also performed to enhance the production of phenylethanol. Mixed
cultures of microorganisms are common in natural ecological systems. They are often used for the
treatment of waste materials discharged from industries, as well as for the production of
bio-based chemicals and bioactive compounds[4]. In the mixed culture, microalgae
could act as an oxygen generator
for the yeast while the yeast provided CO2 to microalgae. It has reported that the
use of
microbial symbiosis has commercial and environmental positive impacts. Beyond the obvious
biomass, there is a more efficient utilization of resources and the reduction or even
elimination of process residues including carbon dioxide and other greenhouse gases to conduct
an increasingly green biotechnology.
Inspiration
When choosing gifts for parents, partners and other elders, do we consider
perfume as a gift? But when we browse Chanel, Dior and other famous perfumes on the shopping
platform, we are confused by their high prices. Why do these perfumes cost so much? Then, we
investigated the composition of perfume and found that phenylethanol is the main ingredient of
perfume with high price. Because of the special nature of phenylethanol in perfume, chemical
synthesis is not desirable, while the price of synthesis by physical extraction and biological
methods is very expensive. So, we planned to use engineered microbial cell to produce
phenylethanol.
After searching the relevant literature, we found that there is an Erich pathway
in S. cerevisiae, which can produce phenylethanol from glucose[5]. In
addition, there is
phenylethylamine pathway in Petunia and Vanda for de novo efficient synthesis of
phenylethylalcohol, and it is simpler and more convenient than the Erlich pathway[6].
More
importantly, it can be uncoupled with cell growth for fractional optimization.
At the same time, we learned that Phenylacetaldehyde synthase consumes oxygen
and releases carbon dioxide when it converts L-phenylalanine to phenylacetaldehyde, and
microalgae consume carbon dioxide and release oxygen, complementing our engineered yeast.
Microalgae can also balance the carbon dioxide concentration and PH of bio-reaction system. So,
our team planned to use the Yeast-Microalgae Consortia to reduce carbon dioxide emissions and
construct a more efficient bio-reaction system. On the one hand, microalgae can absorb carbon
dioxide produced by S. cerevisiae to reduce carbon emissions. On the other hand, the
mixed
system of S. cerevisiae and microalgae was more beneficial to increase the yield,
growth rate
and biomass concentration of high value-added products[7]. This idea also fits into
the newly
released report on peak carbon dioxide emissions and carbon neutrality in China.
References
1. Li, M.; Lang, X.; Moran Cabrera, M.; De Keyser, S.; Sun, X.; Da Silva, N.; Wheeldon, I.,
CRISPR-mediated multigene integration enables Shikimate pathway refactoring for enhanced
2-phenylethanol biosynthesis in Kluyveromyces marxianus. Biotechnol Biofuels 2021, 14 (1), 3.
2. Serra, S.; Fuganti, C.; Brenna, E., Biocatalytic preparation of natural flavours and
fragrances. Trends Biotechnol 2005, 23 (4), 193-8.
3. Wang, S. K.; Wang, X.; Tao, H. H.; Sun, X. S.; Tian, Y. T., Heterotrophic culture of
Chlorella pyrenoidosa using sucrose as the sole carbon source by co-culture with immobilized
yeast. Bioresour Technol 2018, 249, 425-430.
4. Wang, Y.; Zhang, H.; Lu, X.; Zong, H.; Zhuge, B., Advances in 2-phenylethanol production from
engineered microorganisms. Biotechnol Adv 2019, 37 (3), 403-409.
5. Wang, Z.; Bai, X.; Guo, X.; He, X., Regulation of crucial enzymes and transcription factors
on 2-phenylethanol biosynthesis via Ehrlich pathway in Saccharomyces cerevisiae. J Ind Microbiol
Biotechnol 2017, 44 (1), 129-139.
6. Yen, H. W.; Chen, P. W.; Chen, L. J., The synergistic effects for the co-cultivation of
oleaginous yeast-Rhodotorula glutinis and microalgae-Scenedesmus obliquus on the biomass and
total lipids accumulation. Bioresour Technol 2015, 184, 148-152.
7. Arora, N.; Patel, A.; Mehtani, J.; Pruthi, P. A.; Pruthi, V.; Poluri, K. M., Co-culturing of
oleaginous microalgae and yeast: paradigm shift towards enhanced lipid productivity. Environ Sci
Pollut Res Int 2019, 26 (17), 16952-16973.