The constant growth of the bio-diesel production potential in Poland, estimated to be ca. 1 MM tones in 2010, will result in the accumulation of ca. 300,000 tonnes of waste glicerol (as waste product) per year; when selling it, the price of bio-diesel will be impacted. A solution to this problem could be to apply a crude or partially refined glicerol as a component of the medium for micro-organisms producing commercially useful metabolites. In this paper, the potential was studied of utilizing pure glycerol, crude glycerol, and whey (a dairy industry waste) as a source of carbon in the biosynthesis process of propionic acid run by Propionibacterium freudenreichii ssp. shermanii. Furthermore, the efficiency of the process with a culture on standard medium was compared with the process with a propionic bacteria culture. Based on the analysis performed, it was found that the highest concentration of propionic acid (13.7 g/l) was obtained when a medium with pure glycerol as a source of carbon was applied. With other carbon sources applied: crude glycerol, whey, and their combination, the propionic acid production level was similar to the results obtained using a conventional source of carbon, i.e. glucose, and amounted to 10.5 g/l on average. It was also found that with the waste sources used, the fermentation time was extended. Under those conditions, a change in the profile of organic acids being synthesised was reported, too.
glycerol, crude glycerol, whey, propionic acid fermentation