Smells can evoke memories and enhance experiences. Unsurprisingly, a diverse array of aromatic molecules is highly valued across the food, pharmaceutical and cosmetic industries.
Traditionally, nerolidol (a naturally occurring sesquiterpene with a fresh, citrus, and woody aroma) is extracted from botanicals. However, this complex process has been economically and operationally suboptimal, leading to variable yields.
Congqiang Zhang, a Principal Investigator at A*STAR’s Singapore Institute of Food and Biotechnology Innovation (SIFBI) explained: “The primary challenge lies in maintaining a delicate balance between resource allocation for cell growth and nerolidol bioproduction. This is further complicated by the inefficiency of the biosynthetic pathway, particularly due to the limited activity of nerolidol synthases.”
Metabolic engineering, a process that uses genetically engineered microbes to produce desired compounds, has emerged as an efficient, low-cost alternative. Zhang and fellow SIFBI researcher Nicola Tan posited that deploying Escherichia coli can transform nerolidol biosynthesis.
First, the team screened different natural sources in search of the most potent nerolidol synthase, the enzyme that catalyses nerolidol production. “The prediction of in vivo activity for nerolidol synthases is very challenging,” noted Zhang, adding that the team screened enzymes from strategically selected organisms spanning bacteria, fungi and plants, eventually selecting one from the strawberry plant due to its superior activity.
Then, the researchers used genome editing techniques to systematically optimize 16 strains of E. coli for enhanced nerolidol production in industrial bioreactors. Zhang underscored the importance of technologies like CRISPR-Cas9 for accelerating their workflows.
“Previously, it took over a month to delete one gene and recycle the selection marker,” said Zhang. “Now, using marker-free strategies, we can get it done in under a week.”
Validation of these bioengineered strains was conducted at various scales, utilising various renewable carbon sources like glucose, lactose and glycerol. The team is exploring CO2-derived feedstocks like acetate and ethanol to produce nerolidol.
“Our yields surpassed previous benchmarks by between 50 and 190 percent while boosting production rates by two- to four-fold,” said Zhang. “More importantly, the technology developed by the team is a platform that opens for the potential for the biosynthesis of many other high-value natural products.”
These findings support the potential of biosynthesis in producing aromatic compounds efficiently and cost-effectively, which Zhang said promises advances in Singapore’s sustainable biomanufacturing sector.
With a patent secured for their innovation, the researchers are refining their method further using a lactose-based medium to potentially amplify yields, paving the way for commercialisation.
The A*STAR-affiliated researchers contributing to this research are from the Singapore Institute of Food and Biotechnology Innovation (SIFBI).
