Antibiotic-free selection in E. coli: new considerations for optimal design and improved production

Table 3 Evaluation of antibiotic-free system in fermenters (production of rEPA protein)

	Induction at early stage of growth		Induction at advanced stage of growth
	System based on kana resistance	Antibiotic free system	System based on kana resistance	Antibiotic free system
Cell dry weigh (g/L)	28	23	22	24
Plasmid retention (%)	5	100	90	98
Product yield (mg/L)	36	350	280	603
Specific productivity (mg product/gCDW)	1	15	13	25

Two conditions have been analyzed: induction at A₆₀₀ = 25 (advanced stage of growth), close to standard production, and induction at A₆₀₀ = 1 (early stage of growth) to increase the number of cell division between induction and end of fermentation and introduce an extended high level of stress over the cells.
In normal conditions the plasmid maintenance is increased and productivity doubles. For extended stress condition, the differences between antibiotic-free and standard are dramatic, both in terms of plasmid maintenance and protein productivity.

ISSN: 1475-2859