Research progress in strigolactones and application prospect in medicinal plants / 中国中药杂志

Strigolactones(SLs) are a class of sesquiterpenoids derived from the carotenoid biosynthesis pathway with the core carbon skeleton consisting of tricyclic lactone(ABC tricyclic ring) and α,β-unsaturated furan ring(D ring). SLs are widely distributed in higher plants and are symbiotic signals between plants and Arbuscular mycorrhiza(AM), which play key roles in the evolution of plant colonizing terrestrial habitats. As a new type of plant hormone, SLs possess such important biological functions as inhibiting shoot branching(tillers), regulating root architecture, promoting secondary growth, and improving plant stress resistance. Therefore, SLs have attracted wide attention. The biological functions of SLs are not only closely related to the formation of "excellent shape and quality" of Chinese medicinal materials but also have important practical significance for the production of high-quality medicinal materials. However, SLs have been currently widely studied in model plants and crops such as Oryza sativa and Arabidopsis thaliana, and few related studies have been reported on SLs in medicinal plants, which need to be strengthened. This review focused on the latest research progress in the isolation and identification, biological and artificial synthesis pathways, biosynthesis sites and transport modes, signal transduction pathways and mechanisms, and biological functions of SLs, and prospected the research on the regulation mechanism of SLs in the growth and development of medicinal plants and their related application on targeted regulation of Chinese herbal medicine production, which is expected to provide some references for the in-depth research on SLs in the field of Chinese medicinal resources.

Microbial green manufacturing of higher alcohols / 生物工程学报

Higher alcohols that contain more than two carbon atoms have better fuel properties than ethanol, making them important supplements and alternatives to fossil fuels. Using microbes to produce higher alcohols from renewable biomass can alleviate the current energy and environmental crises, and has become a major future direction for green biomanufacturing. Since natural microbes can only produce a few higher alcohols in small amounts, it is necessary to reconstruct the synthetic pathways for higher alcohols in model industrial strains through metabolic engineering and synthetic biology to overcome the metabolic bottlenecks. A series of milestones have been accomplished in past decades. The authors of this review have witnessed the entire journey of this field from its first success to the leaping development. On the 30th anniversary of the founding of the discipline of metabolic engineering, this review dates back to the great milestones in achieving heterologous production of higher alcohols in non-native strains. The design and optimization of high alcohol biosynthetic pathways, the expansion of feedstock, the engineering of host strains and the industrialization process are summarized. This review aims to draw further attention to microbial synthesis of higher alcohols, inspire the development of novel techniques and strategies of metabolic engineering, and promote the innovation and upgrade of China's biofuel industry.

Improving the production of 4-aminobenzoic in engineered Escherichia coli by combinatorial regulation / 生物工程学报

Para-aminobenzoate (PABA) is an important chemical for organic synthesis and extensively used in pharmaceutical and dye industry. In recent years, PABA has received increasing attention as a potential component of high-strength polymer. In Escherichia coli, three genes of pabA, pabB and pabC are responsible for PABA production from chorismate in folate synthetic pathway. However, E. coli does not accumulate or accumulates very few amounts of PABA under normal growth condition. In this study, the tyrosine-producing E. coli TYR002 constructed previously was used as the starting strain for developing PABA-producing strain. First, the activity of bifunctional chorismate mutase/prephenate dehydrogenase TyrA in E. coli TYR002 was weakened to reduce the production of tyrosine. Then, three different constitutive promoters were used to regulate the expression of pabA, pabB and pabC in recombinant plasmid which was transformed into E. coli for improving PABA production. The shake-flask fermentation showed that the different combination of constitutive promoters significantly affected the production of PABA, and the highest shake-flask fermentation titer was 0.67 g/L. After further condition optimization, the engineered E. coli produced 6.4 g/L PABA under 5 L fed-batch fermentation. This study could be a good reference for improving microbial production of PABA.

Improving β-carotene production in Escherichia coli by modularized regulation of the membrane synthetic pathway and morphology engineering / 生物工程学报

Carotenoids are a class of terpenes of commercial interest and exert important biological functions. Engineering morphological and biosynthetic aspects of Escherichia coli cell membrane could improve its storage capacity for β-carotene. However, how the synthesis of phosphatidylethanolamine, the major component of the cell membrane, was not discussed in detail. In this work, the synthesis of phosphatidylethanolamine was divided into three modules to discuss their synergetic effect, by expressing in different combinations. Overexpressing the upstream module 1 in CAR016 caused a 30.5% increase of β-carotene specific production (from 10.1 mg/g to 13.7 mg/g DCW); combined overexpressing module 1 and module 2 in CAR016 led to a 122% increase of β-carotene specific production (from 10.5 mg/g to 22.3 mg/g DCW). The optimal expression combination of the phosphatidylethanolamine synthetic pathway was obtained, which further increased the content of the cell membrane for β-carotene storage, and improved its production. The membrane engineering strategy opens up a new direction for engineering microbial producers for a large spectrum of hydrophobic molecules.