Abstract
Pseudomonas aeruginosa is a producer of desired secondary metabolites, including pyocyanin. Potential uses of this pigment urge a search for improved production methods. Recent trends in bioprocessing show the potential of the use of electromagnetic fields (EMFs) to influence the growth of microorganisms and even modulate the concentration of bioproducts. Here, we aimed at assessing the influence of rotating magnetic field (RMF) and static magnetic field (SMF) on pyocyanin production, growth rate, and respiration of P. aeruginosa. Moreover, exposure time to EMFs (2, 6, and 12 h) and culture volume (10 and 50 ml) were initially assessed. P. aeruginosa was cultivated in magnetically assisted reactors with 5 and 50 Hz RMF (magnetic induction of 24.32 and 42.64 mT, respectively) and SMF (−17.37 mT). Growth kinetics was assessed with Gompertz equation. The viability was tested using resazurin assay, whereas pyocyanin production by chloroform-HCl methodology. The growth of P. aeruginosa was slightly stimulated by exposure to a RMF with 50 Hz (108% related to the control) and significantly by SMF (132% related to the control), while RMF 5 Hz exposure prolonged the time of inflection (in comparison to RMF 50 Hz and SMF). The 6-h exposure to EMFs resulted in the highest pyocyanin production in comparison to the control, indicating a relationship between exposure time and product concentration. Moreover, cultures led in smaller volumes produced more pyocyanin. Our findings show that the use of different EMF types, frequency, and exposition time and volume could be used interchangeably to obtain different bioprocess aims.
Highlights
P. aeruginosa is a bacterium of biotechnological and medical significance, mostly associated with wound infections and cystic fibrosis complications (Bassetti et al, 2018; Grygorcewicz et al, 2020)
The viability of cells during exposure to electromagnetic fields depended on the type of EF and its frequency (Figure 2B)
One-way ANOVA analysis showed significant differences in resazurin assay only for rotating magnetic field (RMF) 50 Hz and static magnetic field (SMF) cultures at 8th hour (95 and 110% related to the control, respectively), and RMF 50 Hz and RMF 5 Hz at 12th hour of incubation (93 and 112% related to the control, respectively)
Summary
P. aeruginosa is a bacterium of biotechnological and medical significance, mostly associated with wound infections and cystic fibrosis complications (Bassetti et al, 2018; Grygorcewicz et al, 2020). It is well-known for the production of pigments, i.e., pyocyanin. Thanks to a high electron transfer capability, pyocyanin found use in colorimetric redox indices and was used as a component of the sensors or the OLED screens (Pierson and Pierson, 2010). Such chemical activity can be used in microbial fuel cells to increase electric output (Feng et al, 2018). Investigating novel methods to increase the pyocyanin production is justified and necessary
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