Study of Metabolic Adaptation of Red Yeasts to Waste Animal Fat Substrate

Abstract

Carotenogenic yeasts are non-conventional oleaginous microorganisms capable to utilize various waste substrates. In this work 4 red yeast strains (Rhodotorula, Cystofilobasidium and Sporobolomyces sp.) were cultivated in media containing crude, emulsified and enzymatically hydrolysed animal waste fat, compared with glucose and glycerol as single C-sources. Cell morphology (cryo-SEM, TEM), production of biomass, lipase, biosurfactants, lipids (GC/FID) carotenoids, ubiquinone, ergosterol (HPLC/PDA) in yeast cells was studied depending on medium composition, C-source and C/N ratio. All studied strains are able to utilize solid and processed fat. Biomass production at C/N=13 was higher on emulsified/hydrolysed fat than on glucose/glycerol. Production of lipids and lipidic metabolites was enhanced for several times on fat; the highest yields of carotenoids (24.8 mg/l) and lipids (54.5%/CDW) were found in S.pararoseus. Simultaneous induction of lipase and biosurfactants was observed on crude fat substrate. Increased C/N ratio (13-100) led to higher biomass production in fat media. Production of total lipids increased in all strains to C/N 50. Oppositely, production of carotenoids, ubiquinone and ergosterol dramatically decreased with increased C/N in all strains. Compounds accumulated in stressed red yeasts are having great application potential and can result from valorization of animal waste fat in the biorefinery concept.Carotenogenic yeasts are non-conventional oleaginous microorganisms capable to utilize various waste substrates. In this work 4 red yeast strains (Rhodotorula, Cystofilobasidium and Sporobolomyces sp.) were cultivated in media containing crude, emulsified and enzymatically hydrolysed animal waste fat, compared with glucose and glycerol as single C-sources. Cell morphology (cryo-SEM, TEM), production of biomass, lipase, biosurfactants, lipids (GC/FID) carotenoids, ubiquinone, ergosterol (HPLC/PDA) in yeast cells was studied depending on medium composition, C-source and C/N ratio. All studied strains are able to utilize solid and processed fat. Biomass production at C/N=13 was higher on emulsified/hydrolysed fat than on glucose/glycerol. Production of lipids and lipidic metabolites was enhanced for several times on fat; the highest yields of carotenoids (24.8 mg/l) and lipids (54.5%/CDW) were found in S.pararoseus. Simultaneous induction of lipase and biosurfactants was observed on crude fat substrate. Increased C/N ratio (13-100) led to higher biomass production in fat media. Production of total lipids increased in all strains to C/N 50. Oppositely, production of carotenoids, ubiquinone and ergosterol dramatically decreased with increased C/N in all strains. Compounds accumulated in stressed red yeasts are having great application potential and can result from valorization of animal waste fat in the biorefinery concept.