Otimização de parâmetros fermentativos industriais de Bradyrhizobium japonicum para produção de inoculante agrícola

Abstract

The increase in the world population demands greater agricultural production, which is why the expansion of practices that help to increase plant productivity is necessary. In this sense, the application of agricultural inoculants in commodities guarantees growth-promoting effects, as is the case with biological nitrogen fixation in soybeans (Glycine max L.) by microorganisms of the species Bradyrhizobium japonicum. This study aims to optimize industrial fermentative parameters for the commercial production of B. japonicum in the Fertibio do Brasil Ltda industry (Ponta Grossa, PR). Initially, an analysis of the work routine employed in the industrial production process was carried out in order to know the process and identify possible critical points. From the diagnosis made, work and process improvements were suggested and implemented in the industry in order to standardize commercial production. Then the optimization of the cell concentration starts of B. japonicum SEMIA 5079 and SEMIA 5080 was performed on a laboratory scale (0.25 L), the cell concentrations of 2.65 107, 8.15107, 2.00 108 and 3.96 108 cells mL-1 were tested in Fertibio [trade mark] culture medium. Strains were cultivated in a shaker-type incubator for 5 days. The results of maximum specific growth speed (µMÁX) and generation time (G) obtained were subjected to analysis of variance (ANOVA) and Tukey's test. The start cell concentration of 2.65 107 cells mL-1 maximizing the fermentative parameters evaluated. This optimized condition was validated on a laboratory scale (9 L), pilot scale (300 L) and industrial scale (1200 L) in Fertibio [trade mark] culture medium. During the production process, an average value of µMÁX of 0.0450 h-1 and G 16.5132 h was obtained, resulting in an average cell growth of 3.3378 109 cells mL-1 after 74 hours of fermentation. In order to identify possible process improvements related to crop scheduling, the designs of two pilot and industrial scale bioreactors were evaluated. The study of the geometry of the bioreactors identified 75% equivalence in relation to the impeller tip speed (Vtip), 87% in relation to the volumetric oxygen transfer coefficient (KLa) and 95% in relation to the mixing time (Tm) of the bioreactors. Changes in the design of the bioreactors and in the operating conditions were identified and pointed out as possibilities for future studies. The results obtained allowed to optimize the process conditions, the cell start concentration of B. japonicum SEMIA 5079 and SEMIA 5080 of the scale-up and the study of the bioreactors project, providing the maximization of the studied fermentative parameters, as well as the control of the development of the bioreactor fermentation. In addition, the study resulted in significant qualitative gains that promote economy and productivity in the Fertibio do Brasil industry.