Resumo

Introduction: Neisseria lactamica shares surface antigens with Neisseria meningitidis. Vaccines to prevent meningococcal disease have been developed from outer membrane vesicles (OMV) from N. meningitidis B. This study aim to compare biomass and OMV yield of this organism, analyze their production and consumption of lactate and organic acids. This work is included in a larger project aiming to develop a potential vaccine against N. meningitidis from OMV of N. lactamica. Methods: Cultivations were performed in 5L bioreactors at 36°C, 0.2 bar, overlay air flow rate of 1L/min, 250 to 850 rpm and 30% oxygen saturation. Samples were taken in every each hour for 12h. Biomass was determined by OD at 540nm, OMV yield by Lowry’s method. The concentration of organic acids and lactate was determined by HPLC at 210nm. Concentrations of acids were calculated using the class VP software. Media tested were: modified Catlin medium MC2LAA and MC2LAA plus yeast extract (MC2LAA-YE. Results and Discussion: Practically no growth of N. lactamica is observed in MC2LAA. The highest biomass of N. lactamica in MC2LAA-YE was 6.04 OD540nm at the 10^th hour and the OMV yield was 160.68mg/L. Lactate was consumed from the beginning until 6^th hours. During this period citrate and acetate was produced. From the 6^th hour, citrate and lactate started to decline, suggesting they may be consumed by the bacteria. In the cultivation of N. meningitidis in the MC2LAA, the highest biomass was 1.45 OD540nm at the 6^th hour and the OMV yield was 29.90mg/L. In the cultivation of N. meningitidis in the MC2LAA-YE the highest biomass was 3.4 OD540nm at the 12^th hour and the OMV yield was 40.21mg/L. In MC2LAA the lactate was almost all consumed at 12^th hour and the bacteria released in small concentrations acetate and succinate and in higher concentrations citrate and malate. In MC2LAA-YE the lactate was not completely consumed at 12^th hour. During growth, bacteria released acetate in lower concentrations than N. lactamica. In this condition it was not observe production of citrate. Conclusion: N. lactamica growth and OMV yield in MC2LAA-YE were bigger than N. meningitidis in both medium. The better results of biomass and OMV yield for N. meningitidis were in MC2LAA-YE, but the 12h of cultivation may be limiting the obtained values.