Phosphoric Acid → (2R,3S,4R,5R)-2,3,4,5,6-pentahydroxyhexanal

Participants

Reaction Steps

One liter fermenters were prepared with 540 mL of medium containing (per L): 6.7 g yeast nitrogen base without amino acids (DIFCO, product #291940); 0.2 g L-leucine; 0.04 g L-tryptophan; 2.8 g yeast synthetic drop-out medium supplements without histidine, leucine, tryptophan and uracil (Sigma, product #Y2001); and 10 mL ethanol. D-glucose (50% w/w) was added fed-batch so that concentration, initially at 30 g/L, varied between 30 and 5 g/L. Temperature was controlled at 30° C. and pH was maintained at pH 5.5 with the addition of either 50% (w/w) NaOH or 20% (w/v) H3PO4. Air was sparged at 0.3 standard liters per min without back pressure and the minimum stir speed was set to 100 rpm. dO was 100% initially and rpm was programmed to control dO at 30%, however, oxygen demand was low and the dO of all fermenters (Runs #1-3 in Table 5) remained in the 90% range throughout the phase of air sparging. In two fermenters (duplicate Runs #2-3), nitrogen sparge replaced air sparge at 35 hrs into the run. Over the course of the fermentations, samples were withdrawn for cell mass (OD600), substrate utilization and by-product distribution measurements. Substrate and by-product concentrations were determined from HPLC analysis. The results are summarized in Table 4, below. Despite the difference in gas sparging between the fermenters, the results were not significantly different. Butanediol (BDO, sum of meso-butanediol and ±-butanediol) was produced at an average concentration of 229 mM with a molar selectivity of 0.63 (mole butanediol produced/moles glucose consumed). The molar selectivity obtained in shake flasks was identical to that obtained in fermenters.

Provenance & Evidence