When all the sugar and the ethanol produced had been consumed, cultivation was stopped and the culture broth was centrifuged at 4,000 rpm for 10 min. The supernatant was discarded and the DM of the harvested cells was determined before use in fermentation.
Unfortunately, it can take as many as five years for the soil to regain its production potential after saltwater cultivation has stopped.
After 24 h cultivation, cells stopped propagation and the OD reached its highest value (1.82), 12% higher than that in the flask experiment.
The results indicated that the concentrations of glucose and xylose decreased over time, and they were 2.6 and 1.1 g/L, respectively, when the cultivation was stopped after 120 hours.
When all the sugars had been consumed as indicated by the O2-sensor, cultivation was stopped and the cells were harvested by centrifugation in 700 mL bottles at 3,600 × g for 10 minutes.
At the end of the exponential growth phase, the cultivations were stopped and the amount of cells was normalized by dilution with 0.9% NaCl to an OD620 of 2.5, which corresponds to approximately 107 colony forming units (CFU) per mL.
As the optimized medium C is glucose limited batch cultivations would stop much earlier compared to cultivations with medium B. Therefore, a fed-batch cultivation was applied for the cultivation of B. subtilis DSM 10T in the optimized medium C. The fermentation plot is shown in Fig. 2.
During the proliferative stage, cells express high levels of E2F3a, B-Myb and phosphorylated forms of retinoblastoma (Rb), but with continued cultivation, cells stop dividing and mature functionally.
