Importance of the C/N-ratio on biomass production and antimicrobial activity from marine bacteria Pseudoalteromonas sp

The main objective of this study was to investigate from the physiological point of view, the influence that nitrogen and carbon sources have on the biomass production and activity of the antimicrobial protein of Pseudoalteromonas sp. The impact of the change in the medium initial C/N-ratio on biomass production and antimicrobial activity against S. aureus MRSA was evaluated using two different carbon sources (glucose or citrate) and a fixed concentration of NH₄Cl as a nitrogen source. The change in total nitrogen concentration in the medium was evaluated using organic or inorganic nitrogen sources (NH₄Cl or yeast extract-peptone) while a fixed glucose concentrations was present. The results showed that the increase in C/N-ratio stimulated biomass production but inhibited antimicrobial activity regardless of the nature of the carbon source. Similarly, the biomass profile and antibiotic activity were dependent in the variation of low nitrogen total concentrations in the medium and especially at concentrations bigger than 3 g L^-1 negatively affected the antimicrobial activity. This indicated that the main factor affected the secondary metabolism of Pseudoalteromonas sp. was the nitrogen concentration over C/N-ratio.

Keywords: C/N-ratio, nitrogen, antimicrobial, marine bacterium, Pseudoalteromonas.