Production of single-cell proteins by yeast Kluyveromyces fragilis on whey

Studirana je mogućnost kultivacije kvasca Kluyveromyces fragilis za proizvodnju mikrobnih proteina na sirutci u šaržnom i kontinuiranom postupku pri pH 5,0-5,5 i temperaturi od 40 °C. Ustanovljeno je eksperimentima na tresilici i laboratorijskom fermentoru da se kvasac dobro razmnožava pri odabranim uvjetima okoline, na 2 %-tnoj deproteiniziranoj sirutci s dodatkom diamonijevog sulfata i kalijevog hidrogen fosfata. Pri optimalnim uvjetima okoline postiže se stupanj konverzije laktoze u kvaščevu biomasu od 0,45-0,55 g s. tv. kvasca/g laktoze, specifična brzina rasta do 0,25 sat^-1 i produktivnost procesa do 1,3 g/L/sat. Kada se osnovnom supstratu doda 0,1 % kvaščevog ekstrakta kvasac se razmnožava brže, specifična brzina rasta poraste na 0,35-0,38 sat^-1, a produktivnost procesa dostiže 1,8 g/L/sat. Ukoliko se voda, potrebna za razrjeđenje sirutke, zamijeni melasnom džibrom, postiže se također povećanje brzine rasta kvasca K. fragilis. Specifična brzina rasta bila je do 0,40 sat^-1, a produktivnost procesa od 2,0-2,4 g/L/satThe possibility of cultivation of the yeast Kluyveromyces fragilis for the production of single-cell protein on deproteinated whey was studied. The hatch and the continuous cultivations were performed at pH 5.0-5.5 and the temperature of 40 °C. By experiments on the shaker and in laboratory fermenter it was established that the yeast cells grow well on 2 % deproteinated whey with the addition of ammonium sulphate and potassium hydrogen phosphate. At optimal conditions the biomass yield was 0.45-0.55 g DM/g lactose with the specific growth rate up to 0.25 h^-1 and productivity of 1.3 g/L/h. When 0.1 % of the yeast extract was added to the basic medium the yeast cells were multiplying faster (μ = 0.35-0.38 h^-1) and productivity was up to 1.8 g/L/h. If the water necessary for the dilution of whey was exchanged with molasses slop a. very good effect attained in the cultivation of yeast cells. The specific growth rate was 0.4 h^-1 and productivity up to 2.4 g/L/h