enhancement of xylose utilization in various escherichia coli strains through adaptive laboratory evolution (ale) experiments

In today’s industrial landscape, utilizing renewable energy sources, such as biomass, rather than non-renewable resources like fossil fuels poses a significant challenge for many chemical production processes. lignocellulosic biomass is one of the abundant biomass sources, and xylose, the second most common sugar in nature, accounts for an average of 24% of the sugars in hydrolyzed lignocellulose. therefore, xylose is a promising renewable source for biofuels and chemical production. on the other hand, escherichia coli high potential for biofuels and valuable chemical production through metabolizing d-xylose has been shown in recent research. genetic engineering tools and adaptive evolution are the most studied methods to improve xylose uptake and metabolism in e.coli. this study evaluated four e. coli, k12, dh5α, bl21, and bw25113 strains under identical conditions of adapting cells to growth on the am1 medium with glucose and subsequently three aerobic subcultures in an am1 medium containing 2 g/l xylose for adaptive laboratory evolution experiments. to accurately compare the adaptation of each strain, the growth curve was plotted using a wavelength of 600 nm, and logarithmic phase-specific growth rate (μ) was calculated. the results showed that the e. coli dh5α strain had the highest adaptation to aerobic conditions with low xylose concentrations compared to other strains. in contrast, the e. coli bl21 showed almost no adaptation to xylose consumption under the defined conditions. therefore, different strains undergo different evolutionary paths under identical conditions, and some adapt better. these findings can contribute to improving the production of biofuels and chemicals from xylose.