Abstract
In the present study, the effects of different nutrient media on the development of Escherichia coli biofilms and the production of a heterologous protein were examined. E. coli JM109(DE3) cells transformed with pFM23 plasmid carrying the gene for enhanced green fluorescent protein (eGFP) expression were used. Cells were grown in two different culture media, Lysogenic Broth (LB) and M9ZB, in a flow cell system for 10 days. Epifluorescence microscopy, fluorimetry, and a high-performance liquid chromatography (HPLC) method based on hydrophobic interaction chromatography (HIC) were used to assess bacterial growth, plasmid copy number (PCN), and eGFP production in both planktonic and biofilm cells. The results showed that biofilm development was favored in M9ZB medium when compared with LB. However, the number of eGFP-expressing cells was higher in LB for both planktonic and sessile states (two-fold and seven-fold, respectively). In addition, the PCN in biofilm cells was slightly higher when using LB medium (on average, 29 plasmids per cell versus 20 plasmids per cell in M9ZB), and higher plasmid stability was observed in biofilms formed in LB compared to their planktonic counterparts. Hence, E. coli biofilms grown in LB enhanced both plasmid stability and capacity to produce the model heterologous protein when compared to M9ZB.
Highlights
Escherichia coli has been one of the most used organisms for heterologous protein production due to its inexpensive and fast high-cell density cultivation, well-known genetics, and large number of cloning vectors [1,2,3]
Despite the few statistical differences, from day 5 onwards, it seems to be a higher cell number of bacteria when growing in Lysogenic Broth (LB) medium, with on average 29% more cells being present in LB than in M9ZB until the end of the experiment
Regarding the number of planktonic culturable cells (Figure 2C), similar behavior was observed for both media, but slightly higher CFU mL−1 values were obtained in M9ZB in all experimental points when compared to LB
Summary
Escherichia coli has been one of the most used organisms for heterologous protein production due to its inexpensive and fast high-cell density cultivation, well-known genetics, and large number of cloning vectors [1,2,3]. Studies in suspension cell cultures have demonstrated that high plasmid copy number imposes a metabolic burden on the host cell, which reduces the bacterial growth rate and favors plasmid instability, thereby decreasing the overall protein yield [7,8]. The presence of plasmids has been shown to stimulate biofilm formation and lead to a higher production of recombinant proteins compared to planktonic cells [10,11,12,13,14,15]. E. coli biofilms were able to produce eGFP at a much higher level (30-fold) than their planktonic counterparts [10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
