Table 1.

Representative examples of the activation of microbial metabolic pathways and phenotype optimization by ALE.

Evolved strain	Evolution/selection conditions	Characteristics of evolved strains	References
S. cerevisiae Y&Z053	The evolving population was subcultured for 45 days in medium with gradually increasing glucose concentrations (from 0.5 to 2%) and decreasing ethanol concentrations (from 2 to 0.5%). Finally, 2% glucose was used as the only carbon source for 50 days of ALE	S. cerevisiae Y&Z053 can produce 33.4 g/L free fatty acids.	(Tao et al. 2018)
E. coli S028	Continuous mutagenesis was performed using CGSS at 30°C.	This evolved strain could produce 38.77 g/L of tryptophan with a yield of 0.164 g/g.	(Chen et al. 2021)
E. coli DSM01	Continuous evolution was carried out for 40 days in medium containing sodium acetate.	The parental strain could not grow in acetate-containing medium, but the evolved strain had a maximum growth rate of 0.061 ± 0.001 h−1.	(Seong et al. 2020)
B. coagulans WT-03	After 15 s of ARTP mutagenesis and 40 days of ALE in media with 0.3% bile salt (pH gradually decreasing from 6.2 to 2.5).	Tolerance to pH 2.5 and 0.3% bile salts with a survival rate of 22.4%.	(Liu et al. 2020)
E. coli GS-2-4	Gradually increase the concentration of 4HPAA (from 15 to 35 g/L) for adaptive evolution.	The 4HPAA titer was 25.42 g/L at 88 h, which was 127.3% higher than that of the parental strain.	(Shen et al. 2022)
E. coli W3110 GE Δung	Gradually increase the concentration of ethanol and isopropanol in a 1% gradient	The tolerance levels of the expression mutants for ethanol and isopropanol increased by 8% and 3%, respectively.	(Eom et al. 2022)
P. tricornutum ALE-Pt1	A total of 30-cycles of continuous culture over 240 days was conducted at a 30 g/L glucose concentration gradient combined with alternating temperatures of 10°C or 20°C.	Biomass increased from 0.84 to 2.19 g/L, lipid content accounted for 33.76% of dry cell weight, with 31.18% of PUFAs in total fatty acids	(Wang et al. 2022)
K. marxianus JKH5 C60	Serially passaged for 60 generations at 42°C in a medium containing 3 g/L acetic acid, 1 g/L furfural, and 1 g/L vanillin.	Growth rate increased from 0.03 to 0.13 h−1 and the evolved strain had 5 times the biomass of the starting strain.	(Hemansi et al. 2022)
E. coli CY02	Adaptive evolution over 1300 generations in M9 minimum medium supplemented with 0.2% (V/V) glycerol.	Improved the final GABA titer and specific productivity by 3.9- and 4.3-fold, respectively.	(Kim et al. 2022)
Z. mobilis Z198	Adaptive evolution was conducted in medium based on corn stover hydrolysate by successive transfer every 24 h for 198 days.	The tolerance to the most toxic phenolic (vanillin) was significantly increased by 6.3-fold, the ethanol productivity reached 0.91 g/L·h, and the ethanol concentration increased by 21.6%.	(Yan et al. 2021)
S. cerevisiae L5EVO	Continuous passaging for 150 generations at 40°C and 100 rpm.	The maximum biomass was 2-fold that of the initial strain, and the time required to consume 50% of the sugar was cut in half.	(Garcia-Rios et al. 2021)
C. cohnii E-D	First increasing the concentration of sethoxydim (from 10 to 60 μM) for 525 days, and then increasing the concentration of sesamol (from 0.5 to 2 mM) for 300 days.	After ALE with 1 mM sesamol, the lipid and DHA production rates of the evolved strain reached 0.046 g/L·h and 0.025 g/L·h, respectively.	(Diao et al. 2019)