Advances of development and application amino acid biosensors / 生物工程学报

Amino acids are the basic building blocks of protein that are very important to the nutrition and health of humans and animals, and widely used in feed, food, medicine and daily chemicals. At present, amino acids are mainly produced from renewable raw materials by microbial fermentation, forming one of the important pillar industries of biomanufacturing in China. Amino acid-producing strains are mostly developed through random mutagenesis- and metabolic engineering-enabled strain breeding combined with strain screening. One of the key limitations to further improvement of production level is the lack of efficient, rapid, and accurate strain screening methods. Therefore, the development of high-throughput screening methods for amino acid strains is very important for the mining of key functional elements and the creation and screening of hyper-producing strains. This paper reviews the design of amino acid biosensors and their applications in the high-throughput evolution and screening of functional elements and hyper-producing strains, and the dynamic regulation of metabolic pathways. The challenges of existing amino acid biosensors and strategies for biosensor optimization are discussed. Finally, the importance of developing biosensors for amino acid derivatives is prospected.

Advances in using adaptive laboratory evolution technology for engineering of photosynthetic cyanobacteria / 生物工程学报

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.

Recent advances in developing enabling technologies for Corynebacterium glutamicum metabolic engineering / 生物工程学报

Corynebacterium glutamicum is an important workhorse of industrial biotechnology, especially for amino acid bioindustry. This bacterium is being used to produce various amino acids at a level of over 6 million tons per year. In recent years, enabling technologies for C. glutamicum metabolic engineering have been developed and improved, which accelerated construction and optimization of microbial cell factoriers, expanding spectra of substrates and products, and facilitated basic researches on C. glutamicum. With these technologies, C. glutamicum has become one of the ideal microbial chasses. This review summarizes recent key technological developments of enabling technologies for C. glutamicum metabolic engineering and focuses on establishment and applications of CRISPR-based genome editing, gene expression regulation, adaptive laboratory evolution, and biosensor technologies.

Advances in adaptive laboratory evolutionary engineering to microbial breeding / 生物工程学报

In recent years, adaptive laboratory evolution (ALE) has emerged as a powerful tool for basic research in microbiology (e.g., molecular mechanisms of microbial evolution) and efforts on evolutionary engineering of microbial strains (e.g., accelerated evolution of industrial strains by bringing beneficial mutations). The ongoing rapid development of next-generation sequencing platforms has provided novel insights into growth kinetics and metabolism of microbes, and thus led to great advances of this technique. In this review, we summarize recent advances in the applications of long-term and short-term ALE techniques mainly for microbial strain engineering, and different modes of ALE are also introduced. Furthermore, we discuss the current limitations of ALE and potential solutions. We believe that the information reviewed here will make a significant contribution to further advancement of ALE.