Recycling Strategy and Repression Elimination for Lignocellulosic-Based Farnesene Production with an Engineered Escherichia coli

Metabolic Engineering for Efficient Production of Z,Z-Farnesol in E. coli

Z,Z-farnesol (Z,Z-FOH), the all-cis isomer of farnesol, holds enormous potential for application in cosmetics, daily chemicals, and pharmaceuticals. In this study, we aimed to metabolically engineer Escherichia coli to produce Z,Z-FOH. First, we tested five Z,Z-farnesyl diphosphate (Z,Z-FPP) synthases that catalyze neryl diphosphate to form Z,Z-FPP in E. coli. Furthermore, we screened thirteen phosphatases that could facilitate the dephosphorylation of Z,Z-FPP to produce Z,Z-FOH. Finally, through site-directed mutagenesis of cis-prenyltransferase, the optimal mutant strain was able to produce 572.13 mg/L Z,Z-FOH by batch fermentation in a shake flask. This achievement represents the highest reported titer of Z,Z-FOH in microbes to date. Notably, this is the first report on the de novo biosynthesis of Z,Z-FOH in E. coli. This work represents a promising step toward developing synthetic E. coli cell factories for the de novo biosynthesis of Z,Z-FOH and other cis-configuration terpenoids.

Cofactor Engineering for Efficient Production of α-Farnesene by Rational Modification of NADPH and ATP Regeneration Pathway in Pichia pastoris

α-Farnesene, an acyclic volatile sesquiterpene, plays important roles in aircraft fuel, food flavoring, agriculture, pharmaceutical and chemical industries. Here, by re-creating the NADPH and ATP biosynthetic pathways in Pichia pastoris, we increased the production of α-farnesene. First, the native oxiPPP was recreated by overexpressing its essential enzymes or by inactivating glucose-6-phosphate isomerase (PGI). This revealed that the combined over-expression of ZWF1 and SOL3 increases α-farnesene production by improving NADPH supply, whereas inactivating PGI did not do so because it caused a reduction in cell growth. The next step was to introduce heterologous cPOS5 at various expression levels into P. pastoris. It was discovered that a low intensity expression of cPOS5 aided in the production of α-farnesene. Finally, ATP was increased by the overexpression of APRT and inactivation of GPD1. The resultant strain P. pastoris X33-38 produced 3.09 ± 0.37 g/L of α-farnesene in shake flask fermentation, which was 41.7% higher than that of the parent strain. These findings open a new avenue for the development of an industrial-strength α-farnesene producer by rationally modifying the NADPH and ATP regeneration pathways in P. pastoris.

Valorization of CO2 to β-farnesene in Rhodobacter sphaeroides

The valorization of CO₂ into valuable products is a sustainable strategy to help overcome the climate crisis. In particular, biological conversion is attractive as it can produce long-chain hydrocarbons such as terpenoids. This study reports the high yield of β-farnesene production from CO₂ by expressing heterologous β-farnesene synthase (FS) into Rhodobacter sphaeroides. To increase the expression of FS, a strong active promoter and a ribosome binding site (RBS) were engineered. Moreover, β-farnesene production was improved further through the supply of exogenous antioxidants and additional nutrients. Finally, β-farnesene was produced from CO₂ at a titer of 44.53 mg/L and yield of 234.08 mg/g, values that were correspondingly 23 times and 46 times higher than those from the initial production of β-farnesene. Altogether, the results here suggest that the autotrophic production of β-farnesene can provide a starting point for achieving a circular carbon economy.

Progress and perspectives for microbial production of farnesene

Farnesene is increasingly used in industry, agriculture, and other fields due to its unique and excellent properties, necessitating its efficient synthesis. Microbial synthesis is an ideal farnesene production method. Recently, researchers have used several strategies to optimize the production performance of microorganisms. This review summarized these strategies, including regulation of farnesene synthesis pathways, and proposed some emerging tools and methods in stain engineering. Meanwhile, new farnesene biosynthetic pathways and effective farnesene production from cheap or waste substrates were emphatically introduced. Finally, future farnesene biosynthesis challenges were discussed.

Recent Advances in the Biosynthesis of Farnesene Using Metabolic Engineering

Farnesene, as an important sesquiterpene isoprenoid polymer of acetyl-CoA, is a renewable feedstock for diesel fuel, polymers, and cosmetics. It has been widely applied in agriculture, medicine, energy, and other fields. In recent years, farnesene biosynthesis is considered a green and economical approach because of its mild reaction conditions, low environmental pollution, and sustainability. Metabolic engineering has been widely applied to construct cell factories for farnesene biosynthesis. In this paper, the research progress, common problems, and strategies of farnesene biosynthesis are reviewed. They are mainly described from the perspectives of the current status of farnesene biosynthesis in different host cells, optimization of the metabolic pathway for farnesene biosynthesis, and key enzymes for farnesene biosynthesis. Furthermore, the challenges and prospects for future farnesene biosynthesis are discussed.

Bifunctional utilization of whey powder as a substrate and inducer for β-farnesene production in an engineered Escherichia coli

β-Farnesene can replace petroleum products as specialty fuel to solve the global fuel energy crisis, but its production by Escherichia coli (E.coli) using glucose and isopropyl β-D-1-thiogalactopyranoside (IPTG) is costly. Hence, we developed a new strategy to produce β-farnesene by engineered E.coli strain F13 with bifunctional utilization of whey powder. The utilization of whey powder as a substrate ensured the growth of the strain F13, while whey powder could also replace IPTG to induce the production of β-farnesene. In shake flasks, β-farnesene production reached 2.41 g/L by the bifunctional utilization of whey powder as a substrate and inducer, 65.1% higher than that with IPTG and glucose. In the 7 L bioreactor, β-farnesene production reached 4.74 g/L using whey powder, which was 197% of that in shake flasks. Therefore, this new strategy might be an attractive route to broaden the applications of whey powder and achieve the economical production of β-farnesene.

First time β-farnesene production by the versatile bacterium Cupriavidus necator

Background

Terpenes are remarkably diverse natural structures, which can be formed via two different pathways leading to two common intermediates. Among those, sesquiterpenes represent a variety of industrially relevant products. One important industrially produced product is β-farnesene as a precursor for a jet fuel additive. So far, microbial terpene production has been mostly limited to known production hosts, which are only able to grow on heterotrophic substrates.

Results

In this paper, we for the first time describe β-farnesene production by the versatile bacterial host Cupriavidus necator on fructose, which is known to grow hetero- and autotrophically and even in bioelectrochemical systems. We were able to show a growth-dependent production of β-farnesene by expressing the β-farnesene synthase from Artemisia annua in C. necator H16 PHB^-4. Additionally, we performed a scale-up in a parallel reactor system with production titers of 26.3 ± 1.3 µM β-farnesene with a fed-batch process.

Conclusions

The β-farnesene production titers reported in this paper are not in the same range as titers published with known heterotrophic producers E. coli or S. cerevisiae. However, this proof-of-principle study with C. necator as production host opens new synthesis routes toward a sustainable economy and leaves room for further optimizations, which have been already performed with the known production strains.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-021-01562-x.