초록
The production of 1,3-propanediol, 2,3-butanediol and ethanol was studied, during cultivations of strain Klebsiella oxytoca FMCC-197 on biodiesel-derived glycerol based media. Different kinds of glycerol feedstocks and experimental conditions had an important impact upon the distribution of metabolic products; production of 1,3-propanediol was positively influenced by stable pH conditions and by the absence of N<SUB>2</SUB> gas infusions throughout the fermentation. Thus, during batch bioreactor fermentations conducted at increasing glycerol concentrations, 1,3-propanediol at 41.3g/L and yield ~47% (w/w) was achieved at initial glycerol concentration ~120g/L. At even higher initial glycerol media (150 and 170g/L), growth was not ceased, but 1,3-propanediol production declined. During fed-batch fermentation under optimal experimental conditions, 126g/L of glycerol were converted into 50.1g/L of 1,3-propanediol. In this experiment, also 25.2g/L of ethanol (conversion yield ~20%, w/w) were formed. A batch-bioreactor culture was performed under non-sterilized conditions and the 1,3-propanediol production was almost equivalent to the sterilized process. Concerning 2,3-butanediol formation, the most detrimental parameter was the absence of N<SUB>2</SUB> sparging and as a result, no 2,3-butanediol was produced. The presence of glucose as co-substrate seriously enhanced 2,3-butanediol production; when commercial glucose was employed as sole substrate, 32.1g/L of 2,3-butanediol were formed.