Fig. 1.

Comparing the conventional genome engineering with CRISPR-mediated genome editing. Conventional genome editing methods heavily rely on the use of selection markers for validation and maintenance of the integrated sequences. Furthermore, conventional techniques need multiple rounds of selection and screening to create and identify positive clones, which is time consuming, leave scars in the genome and reduce the genome stability. CRISPR-mediated genome editing system involve genome cutting and repair, which avoid selection marker integration and recycling. In addition, CRISPR–Cas9 system has the power of multiplex genome editing by cell native repair system. Besides, dCas9 system can be used to regulate the gene expression in metabolic engineering