Cyanobacteria are the only prokaryotes capable of oxygenic photosynthesis, which have potential to serve as “autotrophic cell factories”. However, the synthesis of biofuels and chemicals using cyanobacteria as chassis are suffered from poor stress tolerance and low yield, resulting in low economic feasibility for industrial production. Thus, it's urgent to construct new cyanobacterial chassis by means of synthetic biology. In recent years, adaptive laboratory evolution (ALE) has made great achievements in chassis engineering, including optimizing growth rate, increasing tolerance, enhancing substrate utilization and increasing product yield. ALE has also made some progress in improving the tolerance of cyanobacteria to high light intensity, heavy metal ions, high concentrations of salt and organic solvents. However, the engineering efficiency of ALE strategy in cyanobacteria is generally low, and the molecular mechanisms underpinning the tolerance to various stresses have not been fully elucidated. To this end, this review summarizes the ALE-associated technical strategies and their applications in cyanobacteria chassis engineering, following by discussing how to construct larger ALE mutation library, increase mutation frequency of strains and shorten evolution time. Moreover, exploration of the construction principles and strategies for constructing multi-stress tolerant cyanobacteria, and efficient analysis the mutant libraries of evolved strains as well as construction of strains with high yield and strong robustness are discussed, with the aim to facilitate the engineering of cyanobacteria chassis and the application of engineered cyanobacteria in the future.

Tacrolimus (FK506) is a 23-membered macrolide with immunosuppressant activity that is widely used clinically for treating the rejection after organ transplantation. The research on tacrolimus production was mainly focused on biosynthesis methods, within which there are still some bottlenecks. This review summarizes the progress made in tacrolimus biosynthesis via modification of metabolic pathways and control of fermentation process, with the hope to address the technical bottlenecks for tacrolimus biosynthesis and improve tacrolimus production by fermentation engineering and metabolic engineering.

L-homophenylalanine (L-HPA) is an important non-natural amino acid that has been used as a key intermediate for the synthesis of Puli drugs for the treatment of hypertension. At present, L-HPA is synthesized using chemical methods, which has the disadvantages of expensive raw materials, tedious steps and serious pollution. Therefore, researchers have conducted in-depth research on the enzymatic production of L-HPA. This review summarizes the research progress on the enzymatic synthesis of L-HPA, including the dehydrogenase process, the transaminase process, the hydantoinase process, and the decarboxylase process, with the hope to facilitate the industrial production of L-HPA.