Análise da influência de diferentes impelidores na transferência de oxigênio em biorreatores agitados e efeitos no cultivo de Bradyrizhobium japonicum

Abstract

Inoculants are atmospheric nitrogen-fixing microorganisms when they are symbiotically associated with leguminous plants. Nitrogen is a fundamental macronutrient for plant development, which is why its consumption by rural producers is increasing every year. The inoculant for soy is the most commercialized, since soy is an exotic crop in Brazil and the Brazilian soil lacks specific nitrogen-fixing microorganisms. The increase in inoculant consumption creates the need to increase and optimize its production, which is carried out industrially in bioreactors with mechanical agitation. One of the nitrogen-fixing microorganisms used as an inoculant for soybeans is Bradyrhizobium japonicum, an aerobic bacterium. Industrially, to increase the efficiency in the production of inoculants, changes are traditionally made in the culture medium, pH, temperature, aeration and agitation, but little attention has been given to the design of the bioreactor. The objective of this work is to analyze the influence of different impeller models and their combinations on oxygen transfer in a benchtop bioreactor. The best combination found (Rushton-type agitator at the bottom of the agitation axis and elephant ear 36 mm away) was used to optimize the aeration and agitation parameters in a benchtop bioreactor (2.5L) using a central composite rotational design. The ideal condition was then used in the biomass production of Bradyrhizobium japonicum. An improvement of 5.6% in generation time and 12.5% in microbial growth speed was observed when using the set of paddles that optimize the transfer of oxygen in the bioreactor, which result in an improvement in the production process by reducing time of production.