Growth and nitrite production by Azospirillum strains subjected to different levels of dissolved oxygen in the medium

Azospirillum growth responses to temperature and the capacity of NO3--grown bacteria to produce nitrite, were investigated in three southern Brazilian isolated strains exposed to various concentrations of dissolved oxygen in the medium. The strains Azospirillum brasilense Sp245 and JA04, and A. lipoferum JA03, responded differently to incubation temperature, strain JA03 showing more active growth at the lowest temperature, 25 degrees C, while strains Sp245 and JA04 greater cell multiplication at 32 and 37 degrees C. The exposure of bacteria to different amounts of oxygen dissolved in the medium permitted discrimination of the three strains with respect to growth and nitrite production. Strain JA03 showed remarkably high nitrite accumulation and more intense growth at the lowest oxygen tensions compared with strains Sp245 and JA04. It is conceivable that the highest growth measured in strain JA03 under semi-anaerobic conditions was partly due to efficient utilization of nitrate in respiration. Our data for Azospirillum suggest that the capacity of strain JA03 to withstand reduced oxygen concentrations and relatively lower temperature conditions during growth might be identified as favorable adaptive attributes leading to better acclimation to water-logged and highly compacted sub-tropical soils. (C) 1997 Published by Elsevier Science Ltd.29419841743174

Scale-up from shake flasks to pilot-scale production of the plant growth-promoting bacterium Azospirillum brasilense for preparing a liquid inoculant formulation

Azospirillum brasilense has industrial significance as a growth promoter in plants of commercial interest. However, there is no report in the literature disclosing a liquid product produced in pilot-scale bioreactors and is able to be stored at room temperature for more than 2 years. The aim of this work was to scale up a process from a shake flask to a 10-L lab-scale and 1,000-L pilot-scale bioreactor for the production of plant growth-promoting bacterium A. brasilense for a liquid inoculant formulation. Furthermore, this work aimed to determine the shelf life of the liquid formulation stored at room temperature and to increase maize crops yield in greenhouses. Under a constant oxygen mass transfer coefficient (K L a), a fermentation process was successfully scaled up from shake flasks to 10- and 1,000-L bioreactors. A concentration ranging from 3.5 to 7.5 × 108 CFU/mL was obtained in shake flasks and bioreactors, and after 2 years stored at room temperature, the liquid formulation showed one order of magnitude decrease. Applications of the cultured bacteria in maize yields resulted in increases of up to 95 % in corncobs and 70 % in aboveground biomass. © 2013 Springer-Verlag Berlin Heidelberg