Metabolic engineering can be used to improve bacterial product synthesis yields, modifying metabolic pathways to produce more of the desired product. The product can also be modified, through engineering the enzymes involved in the pathway, allowing the quality to be improved.
Different techniques can be employed to improve product yield and quality.
Modifying the pathways to increase flux to the desired product allows more of the cell’s energy to be directed to product synthesis. This can increase the rate of synthesis (making more in less time) and the concentration produced.
Increasing precursor and energy supply is another strategy to enhance product yield and quality. If there is more energy in the cell, more protein synthesis can occur – this could be done by having a complete growth media and ensuring no nutrient is deficient. Precursor supply can be increased by modifying metabolic pathways.
Engineering transport systems, such as efflux pumps, can change the position of equilibrium to allow more product to be synthesised.
Improving tolerance to the product may help increase yields. If the product is toxic to the cell, such as ethanol, the cell will die and stop producing the product. By improving tolerance, higher concentrations can be obtained before cell death occurs.
Separating growth and synthesis phases can be done in fed-batch fermentations, allowing biomass to be built up quickly before activating synthesis (such as by using an inducible promoter to control expression of the product of interest).