The aim of the present study was to compare the influence of the seed culture medium (YNB or mineral) and the sort of corn steep (liquor or powder) on the biosynthesis of pyruvic and α-ketoglutaric acids from crude glycerol by Yarrowia lipolytica A-10 strain. Batch cultures were carried out until the substrate exhaustion (100 g ∙ dm^-3 of glycerol) and lasted 68–118 h. Yeast produced from 30.4 to 35.8 g ∙ dm^-3 of pyruvic acid and from 14.4 to 17.9 g ∙ dm^-3 of α-ketoglutaric acid. Higher values of volumetric production rate of both acids were achieved when YNB was used as a seed culture medium. The yield of ketoglutaric acid production was similar in all culture variants. However, for pyruvic acid the highest value of this parameter (0,35 g ∙ g^-1) was obtained when mineral medium and corn steep liquor were used. The highest percentage of protein, about 38%, was determined in yeast biomass derived after the culture with mineral seed culture medium.

The use of Mastersizer 2000 particle size analyzer for determination of brewing yeast volume mean diameter was examined. It seems that the best way of cell size measurement is to transfer a biomass sample directly from the growth or fermenting media to the distilled water as a dispersant. The analyzer can be usefull to observe cell size changes in the conditions of osmotic or ethanol stress.

Keratinolytic bacteria Bacillus polymyxa B20 and B. cereus B5esz during cultures in medium with chicken feathers as a sole nutrient source, accumulated various amounts of sulfur compounds at different oxidation level, including thiols, thiosulfate, sulfite and sulfate. The main difference observed between the two tested strains was higher release of sulfate by the former and elevated concentration of thiols by the latter. Additionally, the activity of glutathione reductase, that could potentially play a role in keratinolysis was confirmed, mainly in the cell homogenate fraction, rather than extracellular. Keratinases in crude culture fluids exhibited activity towards soluble keratin preparation, as well as native feather keratin. Application of 2-mercaptoethanol and sulfite, agents that potentially could take part in keratin sulfitolysis, led to a conclusion that they could play a role in keratin degradation, other than activation of extracellular enzymes.