Proizvodnja biomase obogaćene karotenoidima ili ergostorolom s pomoću crvenoga kvasca Rhodotorula glutinis izloženog stresnim uvjetima

The aim of this study is to compare the production of biomass enriched with carotenoids and ergosterol by yeast strain Rhodotorula glutinis CCY 20-2-26 grown under optimal growth conditions and in the presence of exogenous stress factors. R. glutinis cells were exposed to UV irradiation, oxidative stress (2–10 mmol/L H2O2) and osmotic stress (2–10 % NaCl). During the experiment, growth characteristics and the production of biomass, carotenoids and ergosterol were evaluated. Experiments were carried out in Erlenmeyer flasks and in laboratory fermentor. First, R. glutinis cells were exposed to higher concentration of stress factors added into the production medium. Further, low concentrations of NaCl and H2O2 were added to the inoculum medium or to both inoculum and production media. Exposure of red yeast cells to all tested stress factors resulted in higher production of carotenoids as well as ergosterol, while biomass production was changed only slightly. Under high stress, 2–3 times increase of β-carotene was observed. The addition of low salt or peroxide concentration into the inoculation media led to about 2-fold increase of carotenoid production. In Erlenmeyer flasks the best effect on the carotenoid and ergosterol production (3- to 4-fold increase) was exhibited by the combined stress: the addition of low amount of NaCl (2 mmol/L) into the inoculum medium, followed by the addition of H2O2 (5 mmol/L) into the production medium. The production of ergosterol in most cases increased simultaneously with the production of carotenoids. Cultivation of R. glutinis carried out in a 2-litre laboratory fermentor was as follows: under optimal conditions about 37 g/L of yeast biomass were obtained containing approx. 26.30 mg/L of total carotenoids and 7.8 mg/L of ergosterol. After preincubation with a mild stress factor, the yield of biomass as well as the production of carotenoids and ergosterol substantially increased. The best production of enriched biomass was obtained in the presence of peroxide in the inoculation medium (52.7 g/L of biomass enriched with 34 mg/L of carotenoids) and also under combined salt/peroxide or salt/salt stress (about 30–50 g/L of biomass enriched with 15–54 mg/L of total carotenoids and about 13–70 mg/L of ergosterol). R. glutinis CCY 20-2-26 could be used as a potential biotechnological producer of carotenoid-rich biomass.Svrha je ovoga rada usporediti proizvodnju biomase, obogaćene karotenoidima ili ergosterolom s pomoću crvenoga kvasca Rhodotorula glutinis CCY 20-2-26 u optimalnim uvjetima rasta, s proizvodnjom u uvjetima vanjskoga stresa. Stanice R. glutinis bile su izložene UV-zračenju, oksidativnom (2-10 mmol/L H2O2) i osmotskom stresu (2-10 % NaCl). Tijekom pokusa, provedenog u Erlenmeyerovim tikvicama i laboratorijskom fermentoru, procijenjene su karakteristike rasta te proizvodnja biomase, karotenoida i ergosterola. Stanice R. glutinis najprije su izložene većim koncentracijama soli i vodikova peroksida dodanih podlozi za uzgoj, a zatim malim koncentracijama tih spojeva dodanih inokulumu ili inokulumu i podlozi za uzgoj. Izlaganjem stanica kvasca stresnim uvjetima dobivene su veće količine karotenoida ili ergosterola, dok se količina proizvedene biomase nije bitno povećala. Dodatkom veće koncentracije soli ili vodikova peroksida količina se β-karotena povećala 2-3 puta, a dodatkom malih koncentracija tih spojeva inokulumu količina je karotenoida dvostruko porasla. U pokusu provedenom u Erlenmeyerovim tikvicama dobiveno je 3-4 puta više karotenoida i ergosterola (u usporedbi s kontrolnim uzorkom) pri ovim uvjetima: 2 % NaCl je dodano inokulumu, a zatim je 5 mmol/L H2O2 dodano podlozi za uzgoj. Uzgojem R. glutinis u laboratorijskom fermentoru volumena 2 L pri optimalnim je uvjetima dobiveno 37 g/L biomase, obogaćene s 26,3 mg/L karotenoida i 7,8 mg/L ergosterola. Nakon prethodne inkubacije stanica kvasca pod blagim se stresom bitno povećala proizvodnja karotenoida i ergosterola. Najbolji su rezultati postignuti u ovim uvjetima: dodatkom vodikova peroksida dobiveno je 52,7 g/L biomase obogaćene s 34 mg/L karotenoida, a dodatkom soli i vodikova peroksida ili dviju različitih koncentracija soli dobiveno je 30-50 g/L biomase obogaćene s 15-54 mg/L karotenoida i 13-70 mg/L ergosterola. Na kraju je pokusa zaključeno da se R. glutinis CCY 20-2-26 može uspješno upotrijebiti za proizvodnju biomase obogaćene karotenoidima

Production of Carotenoid-/Ergosterol-Supplemented Biomass by Red Yeast Rhodotorula glutinis Grown Under External Stress

The aim of this study is to compare the production of biomass enriched with carotenoids and ergosterol by yeast strain Rhodotorula glutinis CCY 20-2-26 grown under optimal growth conditions and in the presence of exogenous stress factors. R. glutinis cells were exposed to UV irradiation, oxidative stress (2–10 mmol/L H2O2) and osmotic stress (2–10 % NaCl). During the experiment, growth characteristics and the production of biomass, carotenoids and ergosterol were evaluated. Experiments were carried out in Erlenmeyer flasks and in laboratory fermentor. First, R. glutinis cells were exposed to higher concentration of stress factors added into the production medium. Further, low concentrations of NaCl and H2O2 were added to the inoculum medium or to both inoculum and production media. Exposure of red yeast cells to all tested stress factors resulted in higher production of carotenoids as well as ergosterol, while biomass production was changed only slightly. Under high stress, 2–3 times increase of β-carotene was observed. The addition of low salt or peroxide concentration into the inoculation media led to about 2-fold increase of carotenoid production. In Erlenmeyer flasks the best effect on the carotenoid and ergosterol production (3- to 4-fold increase) was exhibited by the combined stress: the addition of low amount of NaCl (2 mmol/L) into the inoculum medium, followed by the addition of H2O2 (5 mmol/L) into the production medium. The production of ergosterol in most cases increased simultaneously with the production of carotenoids. Cultivation of R. glutinis carried out in a 2-litre laboratory fermentor was as follows: under optimal conditions about 37 g/L of yeast biomass were obtained containing approx. 26.30 mg/L of total carotenoids and 7.8 mg/L of ergosterol. After preincubation with a mild stress factor, the yield of biomass as well as the production of carotenoids and ergosterol substantially increased. The best production of enriched biomass was obtained in the presence of peroxide in the inoculation medium (52.7 g/L of biomass enriched with 34 mg/L of carotenoids) and also under combined salt/peroxide or salt/salt stress (about 30–50 g/L of biomass enriched with 15–54 mg/L of total carotenoids and about 13–70 mg/L of ergosterol). R. glutinis CCY 20-2-26 could be used as a potential biotechnological producer of carotenoid-rich biomass