and cytochrome) to design S. cerevisiae strains for high-yielding biological production of artemisinic acid. They also developed an alternate conversion of artemisinic
acid to artemisinin using singlet oxygen instead of dedicated photochemical kit.
Since production in yeast requires enormous quantities of high-priced synthetic
culture medium and huge bioreactors to work in a sterile environment, plant-based
production can potentially provide an inexpensive, renewable and effortlessly measurable artemisinic acid. Fuentes et al. (2016) developed a new SynBio approach—
Combinatorial Super transformation of Transplastomic Recipient Lines (COSTREL), to introduce artemisinic acid synthesis pathway into chloroplast genome
of tobacco. The transplastomic plants were supertransformed with enzymes altering
flux through the synthetic pathway, thereby further optimizing the metabolic productivity of engineered artemisinin (Fuentes et al. 2016).
Raspberry ketone, chief aroma compound in raspberries, is a valuable flavouring
agent. Again the high production cost along with poor yields from plant tissue,
makes it an excellent objective for heterologous construction in microbial strains.
Lee et al. (2016) combined the best possible enzymes of ketone synthetic pathway
from a wide range of plant genomes to synthetically design a yeast strain that
produced more than double ketone when compared to host plants. Lee et al.
(2016) represented a de novo pathway by assembling four heterologous genes,
encoding phenylalanine/tyrosine ammonia lyase, cinnamate-4-hydroxlase,
coumarate-CoA ligase and benzalacetone synthase for the production of raspberry
ketone in an industrial strain of S. cerevisiae (Lee et al. 2016). Growing chocolate
demands and limited Cocoa butter (CB—raw material for chocolate production
extracted from cocoa beans) manufacture has resulted in a scarce supply of
CB. CB is largely composed of C16 and C18 triacylglycerols (TAGs). Interestingly,
Wei et al. (2017) suggested that S. cerevisiae have potential as CB-like lipids (CBL)
production chassis, as storage lipids (mainly TAGs) of yeasts, also have relatively
high-level of C16 and C18 fatty acids. In their study, they cultivated six different
yeasts, S. cerevisiae, Trichosporon oleaginosus, Rhodotorula graminis, Lipomyces
starkeyi, Rhodosporidium toruloides and Yarrowia lipolytica in N-limited medium.
In all the six yeasts TAGs were the main lipids but comparatively T. oleaginosus
could yield the highest amount of TAGs. However, Wei et al. (2018) reported that
major TAG forms in yeast were not similar to CBL, thus necessitating the modulation of yeast TAG biosynthetic pathway for better CBL production. They cloned
seven glycerol-3-phosphate acyltransferase (GPAT) genes and three
lysophospholipid acyltransferase (LPAT) genes from cocoa cDNA. By expressing
these cloned cocoa genes with two synthesized cocoa diacylglycerol acyltransferase
(DGAT) genes in S. cerevisiae, they significantly increased CBL production in some
of the strains, suggesting that this strategy might be accountable for CBL biosynthesis in the future.
Cannabinoids are a group of more than 100 chemical compounds (Radwan et al.
2008) mainly isolated from the strictly regulated Cannabis sativa L. Δ9tetrahydrocannabinolic acid (THCA) and cannabidiol (CBD) are important drug
candidates (Carvalho et al. 2017). The supply of cannabinoids is inadequate since
most of the cannabinoids can only be extracted in very low amounts.
470
P. Singla
acid to artemisinin using singlet oxygen instead of dedicated photochemical kit.
Since production in yeast requires enormous quantities of high-priced synthetic
culture medium and huge bioreactors to work in a sterile environment, plant-based
production can potentially provide an inexpensive, renewable and effortlessly measurable artemisinic acid. Fuentes et al. (2016) developed a new SynBio approach—
Combinatorial Super transformation of Transplastomic Recipient Lines (COSTREL), to introduce artemisinic acid synthesis pathway into chloroplast genome
of tobacco. The transplastomic plants were supertransformed with enzymes altering
flux through the synthetic pathway, thereby further optimizing the metabolic productivity of engineered artemisinin (Fuentes et al. 2016).
Raspberry ketone, chief aroma compound in raspberries, is a valuable flavouring
agent. Again the high production cost along with poor yields from plant tissue,
makes it an excellent objective for heterologous construction in microbial strains.
Lee et al. (2016) combined the best possible enzymes of ketone synthetic pathway
from a wide range of plant genomes to synthetically design a yeast strain that
produced more than double ketone when compared to host plants. Lee et al.
(2016) represented a de novo pathway by assembling four heterologous genes,
encoding phenylalanine/tyrosine ammonia lyase, cinnamate-4-hydroxlase,
coumarate-CoA ligase and benzalacetone synthase for the production of raspberry
ketone in an industrial strain of S. cerevisiae (Lee et al. 2016). Growing chocolate
demands and limited Cocoa butter (CB—raw material for chocolate production
extracted from cocoa beans) manufacture has resulted in a scarce supply of
CB. CB is largely composed of C16 and C18 triacylglycerols (TAGs). Interestingly,
Wei et al. (2017) suggested that S. cerevisiae have potential as CB-like lipids (CBL)
production chassis, as storage lipids (mainly TAGs) of yeasts, also have relatively
high-level of C16 and C18 fatty acids. In their study, they cultivated six different
yeasts, S. cerevisiae, Trichosporon oleaginosus, Rhodotorula graminis, Lipomyces
starkeyi, Rhodosporidium toruloides and Yarrowia lipolytica in N-limited medium.
In all the six yeasts TAGs were the main lipids but comparatively T. oleaginosus
could yield the highest amount of TAGs. However, Wei et al. (2018) reported that
major TAG forms in yeast were not similar to CBL, thus necessitating the modulation of yeast TAG biosynthetic pathway for better CBL production. They cloned
seven glycerol-3-phosphate acyltransferase (GPAT) genes and three
lysophospholipid acyltransferase (LPAT) genes from cocoa cDNA. By expressing
these cloned cocoa genes with two synthesized cocoa diacylglycerol acyltransferase
(DGAT) genes in S. cerevisiae, they significantly increased CBL production in some
of the strains, suggesting that this strategy might be accountable for CBL biosynthesis in the future.
Cannabinoids are a group of more than 100 chemical compounds (Radwan et al.
2008) mainly isolated from the strictly regulated Cannabis sativa L. Δ9tetrahydrocannabinolic acid (THCA) and cannabidiol (CBD) are important drug
candidates (Carvalho et al. 2017). The supply of cannabinoids is inadequate since
most of the cannabinoids can only be extracted in very low amounts.
470
P. Singla