Pretreatment of raw glycerol with activated carbon for 1,3-propanediol production by Clostridium butyricum

Raw glycerol contains inhibiting impurities that render its bioconversion difficult. In this work, raw glycerol used in 1,3-propanediol fermentation by Clostridium butyricum was pretreated with activated carbon. Compared with pure glycerol, the untreated raw glycerol inhibited fermentation. Therefore, the raw glycerol was treated using dusty activated carbon as an adsorbent in batch fermentation, resulting in a shortening of the fermentation time from 18.5 to 13.3 h. The effects of pH, dusty activated carbon amount, and adsorption time on the pretreatment results were investigated using uniform design. The pH had a much lower impact and the optimal pretreatment conditions were achieved: pH 3.0, 0.5 g dusty activated carbon/150 g raw glycerol, adsorption time 3 h. Batch cultures on pretreated raw glycerol were comparable to those on pure glycerol. The 1,3-propanediol concentration in fed-batch cultivation was 49.3 g/L on pretreated raw glycerol while it was 40.8 g/L on untreated raw glycerol. The FTIR spectra of dusty activated carbon before and after adsorption indicated that the inhibiting impurities were probably aromatic compounds. This work indicates that pretreatment is necessary to ferment raw glycerol to 1,3-propanediol and that pretreatment with dusty activated carbon is an efficient, economical, and simple method.