The effects of several factors on the growth of pure and mixed cultures of Azotobacter chroococcum and Bacillus subtilis

Cultivation of the bacterium Azotobacter chroococcum for preparation of biofertilizers

“…The maximal value of biomass concentration was higher than that obtained in the cultivation on chemically defined medium and much higher than the values obtained in flask culture on the rotary shaker. The obtained data are in agreement with those in literatures (Quagliano et al, 2001;Kisten et al, 2006).…”

“…Cultivation of A. chroococcum on chemically defined media was characterized by relatively low biomass yield coefficients (Y X/S ; 0.103 to 0.166 g/g), which is probably a consequence of relatively high energy demand for bacterial metabolism, as already reported in literature (Yates et al, 1997;Savenkova et al, 1999;Kisten et al, 2006).…”

“…Cultivation of A. chrooccocum is characterised by relatively low dry biomass concentrations (MartinezToledo et al, 1995;Quagliano et al, 2001;Pozo et al, 2002;Kisten et al, 2006) and therefore, it is necessary to examine different cultivation techniques (batch, fed batch, semi-continuous or continuous) in order to obtain higher cell yield. In bioprocess industry, batch and fed batch techniques are still most often used.…”

“…The growth of A. chroococcum is affected by temperature that has to be in the range of 28 to 32°C, while the pH should be kept between 7.0 and 7.5. Dissolved oxygen concentration and medium composition (especially salt concentration) have also considerable impact on the bacterial growth (Lees and Postgate, 1973;Hine and Lees, 1976;Pozo et al, 2002;Kisten et al, 2006). Some nitrogen containing salts, promote bacterial growth by reducing the duration of the lag phase (Juarez et al, 2005).…”

“…It is mostly used for microbial biomass production (yeast and bacteria) and waste water treatment (Moser, 1988). Until now, batch and fed batch cultivation techniques were mostly used for the study of the growth of A. chroococcum in different conditions (Savenkova et al, 1999;Quagliano et al, 2001;Kisten et al, 2006). Continuous cultivation of A. chroococum was performed in order to study the bacterial physiology in different experimental conditions (Lees and Postgate, 1973;Hine and Lees, 1976).…”