Optimizing alternative substrate for simultaneous production of surfactin and 2,3-butanediol by Bacillus subtilis LB5a

Comparative study: bench-scale surfactin production from bacillus subtilis using analytical grade and concentrated glycerol from the biodiesel industry

“…All culture media were adjusted to pH 7 with NaOH 0.05 M. The erlenmeyer flasks, containing each culture medium (100 mL), were inoculated and then incubated at 150 rpm and 30 o C. Samples (≈ 12 mL) of the culture medium were collected on a 12-hour basis and centrifuged at 10 4 g for 10 minutes at 5 o C. Finally, the viable cell count, surface tension (ST) of the samples and their dilutions were analyzed [15][16][17].…”

“…The process conditions were: 150 rpm, 30 o C and an aeration rate (air) of 0.266 vvm (maximum aeration pump capacity available) [16][17]. The dissolved oxygen (DO) sensor (Mettler Toledo -INPRO 6830/12/320) was set to measure every thirty seconds during the entire fermentation process.…”

“…The dissolved oxygen (DO) sensor (Mettler Toledo -INPRO 6830/12/320) was set to measure every thirty seconds during the entire fermentation process. Samples (≈ 30 mL) of the culture medium were collected on a 24-hour basis, and subsequently the viable cell count, ST dilutions and consumption of glycerol were used as process parameters [2], [15][16][17]. Foam was collected during production from the top of the bench-scale bioreactor (foam overflow) into a Büchner flask through a hose [15][16].…”

“…Two purification methods were applied: (1) acid precipitation method and (2) acid precipitation followed by solvent extraction (chloroform: methanol-81:19) and solvent evaporation [15][16][17]. The resulting product (in powder form) from (1) was named crude biosurfactant and the product from (2) semi-purified biosurfactant.…”

“…Viable cellular growth curves were plotted using CFU/mL data [15][16][17]. The data of DO were obtained from a probe submerged in the culture medium.…”