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- New dual-stage pH control fed-batch cultivation strategy for the improvement of lipids and carotenoids production by the red yeast Rhodosporidium toruloides NCYC 921Publication . Dias, Carla; Sousa, Sofia; Caldeira, João; Reis, Alberto; Silva, Teresa Lopes daThe optimal medium pH to produce biomass and fatty acids by the red yeast Rhodosporidium toruloides NCYC 921 is 4.0, and to produce carotenoids is 5.0. Based on this difference, a dual-stage pH control fed-batch cultivation strategy for the enhancement of lipids and carotenoids production by this yeast was studied. The results showed that when the yeast growth phase was conducted at pH 4.0, and the products accumulation phase was conducted at pH 5.0, biomass, total fatty acid and total carotenoid productivities were significantly improved comparing with the yeast fed batch cultivations carried out at fixed medium pH (4 or 5). Under dual-stage pH control conditions, the biomass, carotenoids and lipids productivities attained 2.35 g/L h, 0.29 g/L h and 0.40 g/L h, respectively. It was also observed that the oxygen played a major role in the yeast carotenoid production.
- Lipid and carotenoid production by a Rhodosporidium toruloides and Tetradesmus obliquus mixed culture using primary brewery wastewater supplemented with sugarcane molasses and ureaPublication . Dias, Carla; Nobre, B. P.; Santos, J. A. L.; Reis, Alberto; Silva, Teresa Lopes daABSTRACT: In this study, Rhodosporidium toruloides and Tetradesmus obliquus were used for lipid and carotenoid production in mixed cultures using primary brewery wastewater (PBWW) as a culture medium, supplemented with sugarcane molasses (SCM) as a carbon source and urea as a nitrogen source. To improve biomass, lipid, and carotenoid production by R. toruloides and T obliquus mixed cultures, initial SCM concentrations ranging from 10 to 280 g L-1 were tested. The medium that allowed higher lipid content (26.2% w/w dry cell weight (DCW)) and higher carotenoid productivity (10.47 mu g L-1 h(-1)) was the PBWW medium supplemented with 100 g L-1 of SCM and 2 g L-1 of urea, which was further used in the fed-batch mixed cultivation performed in a 7-L bioreactor. A maximum biomass concentration of 58.6 g L-1 and maximum lipid content of 31.2% w/w DCW were obtained in the fed-batch cultivation. PBWW supplemented with SCM was successfully used as a low-cost medium to produce lipids and carotenoids in a R. toruloides and T obliquus mixed culture, with higher productivities than in pure cultures, which can significantly reduce the cost of the biofuels obtained.
- Sequential carotenoids extraction and biodiesel production from Rhodosporidium toruloides NCYC 921 biomassPublication . Passarinho, Paula; Oliveira, Bruno; Dias, Carla; Teles, Marta; Reis, Alberto; Silva, Teresa Lopes daABSTRACT: A new process for co-extraction and separation of fatty acids and carotenoids from Rhodosporidium toruloides NCYC 921 biomass in order to achieve full exploitation of the yeast lipidic fraction is described. A saponification of the wet yeast biomass was performed using a potassium hydroxide solution (1.1 M) in ethanol 96%, at 65 °C for 180 min. In the carotenoid extraction step, a biphasic system with an organic: aqueous phases ratio of 0.49 mL/mL and a water content of 18.9% (w/w) was used. In the presence of an acid catalyst, the fatty acid fraction was esterified into fatty acids ethyl esters. The yeast biomass downstream processing allowed reaching a fatty acid and total carotenoids recovery yields of 91.0% and 85.2%, respectively. The process reported here takes advantage of various components of the yeast biomass, therefore maximizing the value derived from the biomass feedstock, with a minimal environmental impact within the frame of circular bioeconomy.
- Carob pulp syrup : a potential Mediterranean carbon source for carotenoids production by Rhodosporidium toruloides NCYC 921Publication . Martins, Vasco; Dias, Carla; Caldeira, João; Duarte, Luís C.; Reis, Alberto; Silva, Teresa Lopes daABSTRACT: Carob pulp syrup (CPS) was used as carbon source to produce carotenoids from Rhodosporidium toruloides. To increase the carbon concentration in the growth medium aiming at the carotenoid production improvement, the CPS was concentrated and two different total sugar (TS) concentrations (195.6 g/L and 548.7 g/L) were studied. CPS 195.6 g/L TS contained 4.1 g/L and 0.7 g/L of hydroxymethyl furfural (HMF) and furfural, respectively. CPS 548.7 g/L TS contained 17.7 g/L of HMF and 1.2 g/L of furfural, respectively. >42% of metabolically active cells (with intact membrane and enzymatic activity) were detected throughout the course of the yeast cultivation on CPS 195.6 g/L TS. On the contrary, the proportion of metabolically active cells was always below 28% during the yeast cultivation on CPS 548.7 g/L TS. Nevertheless, the maximum carotenoid content and productivity (0.42 mg/g and 0.43 mg/Lh, respectively) were obtained when using CPS 548.7 g/L TS.
- Direct lipid and carotenoid extraction from Rhodosporidium toruloides broth culture after high pressure homogenization cell disruption: Strategies, methodologies, and yieldsPublication . Dias, Carla; Nobre, B. P.; Santos, J. A. L.; Silva, Teresa Lopes da; Reis, AlbertoABSTRACT: Biodiesel produced from oleaginous microorganisms is considered an appealing option since oleaginous yeasts and microalgae can accumulate between 20 % and 80 % lipids of their dry cell weight. However, it is still not economically sustainable since production costs are still high. This work developed a new mild protocol using hexane or sunflower oil as extraction solvents to simultaneously extract lipids and carotenoids from Rhodosporidium toruloides biomass directly from the broth culture without using any harvesting technique after performing high pressure homogenization to disrupt the yeast cells. The highest results were obtained for the hexane extractions attaining 55.9 % of total lipids (w/w) and 111.5 mu g g-1 (eq. torulene) of carotenoids, which are higher values than the ones obtained using lipid extraction traditional methods. The process here presented is an easy, simple, inexpensive and environmentally friendly methodology which involves the simultaneous extraction of carotenoids and lipids directly from R. toruloides broth culture which has never been reported before and can greatly improve the economics of the biodiesel production process.