Industrial yeasts from the brewing process.
Live, aerobic yeast cells possess dehydrogeneases which reduce the methylene blue absorbed into the cell to its colourless leuco form, giving the cells a pale blue colour. Dead or inactive cells lack dehydrogenase activity and turn an intense blue colour.
Brewing yeasts
Analysis of yeasts for dead cells using propidium iodide in a cell counter.
Wastewater generated in the industrial production of beer and food
Well-mixed wastewater is poured into an Imhoff funnel, and the volume of sludge is recorded using the volumetric scale on the graduated cylinder after a settling time of two hours.
After decanting the supernatant, the deposits are quantitatively transferred to a platinum dish in which, after drying at 105 °C, the dry residue after evaporation is determined by weight.
After annealing in a muffle furnace at 550 °C for 30 min, the ash content is determined gravimetrically.
The annealing losses are calculated from the difference in weight between the dry residue after evaporation and the ash content.