Application of Multiple Strategies To Debottleneck the Biosynthesis of Longifolene by Engineered Saccharomyces cerevisiae

Application of multiple strategies to enhance oleanolic acid biosynthesis by engineered Saccharomyces cerevisiae

Oleanolic acid and its derivatives are widely used in the pharmaceutical, agricultural, cosmetic and food industries. Previous studies have shown that oleanolic acid production levels in engineered cell factories are low, which is why oleanolic acid is still widely extracted from traditional medicinal plants. To construct a highly efficient oleanolic acid production strain, rate-limiting steps were regulated by inducible promoters and the expression of key genes in the oleanolic acid synthetic pathway was enhanced. Subsequently, precursor pool expansion, pathway refactoring and diploid construction were considered to harmonize cell growth and oleanolic acid production. The multi-strategy combination promoted oleanolic acid production of up to 4.07 g/L in a 100 L bioreactor, which was the highest level reported.

Biosynthesis Progress of High-Energy-Density Liquid Fuels Derived from Terpenes

High-energy-density liquid fuels (HED fuels) are essential for volume-limited aerospace vehicles and could serve as energetic additives for conventional fuels. Terpene-derived HED biofuel is an important research field for green fuel synthesis. The direct extraction of terpenes from natural plants is environmentally unfriendly and costly. Designing efficient synthetic pathways in microorganisms to achieve high yields of terpenes shows great potential for the application of terpene-derived fuels. This review provides an overview of the current research progress of terpene-derived HED fuels, surveying terpene fuel properties and the current status of biosynthesis. Additionally, we systematically summarize the engineering strategies for biosynthesizing terpenes, including mining and engineering terpene synthases, optimizing metabolic pathways and cell-level optimization, such as the subcellular localization of terpene synthesis and adaptive evolution. This article will be helpful in providing insight into better developing terpene-derived HED fuels.

Sequential catalytic lignin valorization and bioethanol production: an integrated biorefinery strategy

BACKGROUND

The effective valorization of lignin and carbohydrates in lignocellulose matrix under the concept of biorefinery is a primary strategy to produce sustainable chemicals and fuels. Based on the reductive catalytic fractionation (RCF), lignin in lignocelluloses can be depolymerized into viscous oils, while the highly delignified pulps with high polysaccharides retention can be transformed into various chemicals.

RESULTS

A biorefinery paradigm for sequentially valorization of the main components in poplar sawdust was constructed. In this process, the well-defined low-molecular-weight phenols and bioethanol were co-generated by tandem chemo-catalysis in the RCF stage and bio-catalysis in fermentation stage. In the RCF stage, hydrogen transfer reactions were conducted in one-pot process using Raney Ni as catalyst, while the isopropanol (2-PrOH) in the initial liquor was served as a hydrogen donor and the solvent for lignin dissolution. Results indicated the proportion of the 2-PrOH in the initial liquor of RCF influenced the chemical constitution and yield of the lignin oil, which also affected the characteristics of the pulps and the following bioethanol production. A 67.48 ± 0.44% delignification with 20.65 ± 0.31% of monolignols yield were realized when the 2-PrOH:H2O ratio in initial liquor was 7:3 (6.67 wt% of the catalyst loading, 200 °C for 3 h). The RCF pulp had higher carbohydrates retention (57.96 ± 2.78 wt%), which was converted to 21.61 ± 0.62 g/L of bioethanol with a yield of 0.429 ± 0.010 g/g in fermentation using an engineered S. cerevisiae strain. Based on the mass balance analysis, 104.4 g of ethanol and 206.5 g of lignin oil can be produced from 1000 g of the raw poplar sawdust.

CONCLUSIONS

The main chemical components in poplar sawdust can be effectively transformed into lignin oil and bioethanol. The attractive results from the biorefinery process exhibit great promise for the production of valuable biofuels and chemicals from abundant lignocellulosic materials.

Recent Advances on the Production of Itaconic Acid via the Fermentation and Metabolic Engineering

Itaconic acid (ITA) is one of the top 12 platform chemicals. The global ITA market is expanding due to the rising demand for bio-based unsaturated polyester resin and its non-toxic qualities. Although bioconversion using microbes is the main approach in the current industrial production of ITA, ecological production of bio-based ITA faces several issues due to: low production efficiency, the difficulty to employ inexpensive raw materials, and high manufacturing costs. As metabolic engineering advances, the engineering of microorganisms offers a novel strategy for the promotion of ITA bio-production. In this review, the most recent developments in the production of ITA through fermentation and metabolic engineering are compiled from a variety of perspectives, including the identification of the ITA synthesis pathway, the metabolic engineering of natural ITA producers, the design and construction of the ITA synthesis pathway in model chassis, and the creation, as well as application, of new metabolic engineering strategies in ITA production. The challenges encountered in the bio-production of ITA in microbial cell factories are discussed, and some suggestions for future study are also proposed, which it is hoped offers insightful views to promote the cost-efficient and sustainable industrial production of ITA.