Autotrophic cultures growth

If inorganic substrates are replaced by organic substrates in the culture medium, then contamination may result from the growth of heterotrophic Acidiphilium species or facultatively autotrophic Thiobacillus acidophilus (see Section II,A,5). 

Cultivation of the cyanobacterium was performed in a 4.35 L automated helical photobioreactor (PhBR) described by Tsygankov et al. (1998a). A. variabilis PK 84 was cultivated autotrophically in the PhBR under sterile air containing 2% C02 (500 ml-min 1). Growth conditions in the PhBR were monitored by a computer system connected to built-in pH, temperature, optical density, pO, and sunlight intensity sensors. When necessary 1 or 2 polyurethane foam balls were circulated along with the culture in the PhBR to clean the inner surface of the PVC tubing. 

For the growth of hydrogen bacteria under autotrophic conditions in submerged mass culture, the nutrient solution described above may be used only ammonia may become growth-limiting and an additional... 

By using colistine for the enrichment procedure, many auxotrophic mutants defective in the biosynthetic pathway of valine and isoleucine have been isolated. From an isoleucine-requiring mutant, defective in threonine desaminase, a prototrophic revertant has been isolated. The threonine desaminase of this revertant differs from the wild type enzyme in that its affinity for isoleucine is diminished. This revertant excretes isoleucine. Another revertant of an isoleucine-deficient mutant was obtained which formed the enzyme acetohydroxy add synthetase constitutively. During heterotrophic growth with fructose or lactate as substrates, valine, isoleucine and leucine were excreted into the culture medium. Approximately 0.6 g of amino acids were produced per liter suspension when lactate was supplied as a substrate under autotrophic conditions the excretion was negligible (Reh, 1970 Fig. 12). 

Figure 7A. Cell density of the generalist (mixotroph T. A2, O) and the autotroph (specialist T. neapolitanus, 9) in mixed chemostat culture at steady state, growing at a dilution rate of 0.075 h. Growth was simultaneously limited by thiosulfate (reservoir medium concentration, =40 mM) and by increasing concentrations of acetate in the reservoir medium (S ° = 0-10 mM).

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