Browsing by Author "Carvalho, Bernardo"
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- Development of an organic culture medium for autotrophic production of chlorella vulgaris biomassPublication . Machado, Adriana; Pereira, Hugo; Costa, Margarida; Santos, Tamara; Carvalho, Bernardo; Soares, Maria; Quelhas, Pedro; Silva, Joana T.; Trovão, Mafalda; Barros, Ana; Varela, João; Vicente, António A.; Silva, JoanaMicroalgal biomass has gained increasing attention in the last decade for various biotechnological applications, including human nutrition. Certified organic products are currently a growing niche market in which the food industry has shown great interest. In this context, this work aimed at developing a certified organic culture medium for the production of autotrophic Chlorella vulgaris biomass. A preliminary assay in 2 L bubble column photobioreactors was performed in order to screen di erent commercial organic substrates (OS) at a normalized concentration of N (2 mmol L1). The highest growth performance was obtained using EcoMix4 and Bioscape which showed similar biomass concentrations compared to the synthetic culture medium (control). In order to meet the nutrient needs of Chlorella, both OS underwent elemental analyses to assess their nutrient composition. The laboratory findings allowed the development of a final organic culture medium using a proportion of Bioscape/EcoMix4 (1:1.2, m/m). This organic culture medium was later validated outdoors in 125 L flat panel and 10 m3 tubular flow through photobioreactors. The results obtained revealed that the developed organic medium led to similar microalgal growth performance and biochemical composition of produced biomass, as compared to the traditional synthetic medium. Overall, the formulated organic medium was e ective for the autotrophic production of organic C. vulgaris biomass.
- Influence of different processing techniques on microalgal protein extractionPublication . Moreira, Catarina; Ferreira-Santos, Pedro; Nunes, Rafaela; Carvalho, Bernardo; Pereira, Hugo; Teixeira, José A.; Rocha, Cristina M.R.The nutrient-rich composition of microalgae biomass positions it as a highly promising natural food ingredient. This holds the potential to not only enhance the nutritional value of various food products but also simultaneously alter their structural attributes.This work investigated the effect of five protein extraction techniques such as freeze-thawing, enzymatic-assisted extraction, high-pressure homogenization, ultrasounds-assisted extraction, and pH adjustment (pH 7, pH 10, and pH 13) in protein yield, and subsequente cell and protein structure of three microalgal suspensions, namely, Chlorella vulgaris, Nannochloropsis oceanica, and Tetraselmis chui. In Chlorella vulgaris, freeze- thawing and high-pressure homogenization exhibited a higher effect in terms of protein yield (similar to 26.60 g (protein) /100 g (protein microalgae)). The same occurred for Nannochloropsis oceanica with also ultrasounds-assisted extractions and pH 7 and 10 having a protein yield above 30 %. Tetraselmis chui was similar to Chlorella vulgaris (>20.00 g (protein) /100 g (protein microalgae)) for freeze-thawing, high-pressure homogenization and ultrasound-assisted extraction. Enzymatic-assisted had a the lower protein yield for all the three microalgae (<10.00 g (protein) /100 g (protein microalgae)). The majority of proteins extracted from Chlorella vulgaris samples had molecular weights exceeding 337 kDa, whereas proteins extracted from Nannochloropsis and Tetraselmis had molecular weights ranging from 5 to 50 kDa. alpha-helices occurred in proteins extracted from Chlorella vulgaris through freeze-thawing and enzymatic-assisted extraction, while Nannochloropsis and Tetraselmis only had beta-sheet. In conclusion, for optimal protein yield recovery, methodologies such as freeze-thawing and high-pressure homogenization are the most efficient across all studied microalgae. The method selected for extraction had a greater impact on both the protein yield and structure for spray-dried cells.
- Isolation and characterization of novel chlorella vulgaris mutants with low chlorophyll and improved protein contents for food applicationsPublication . Lisa Schueler, Lisa M. Schueler; Morais, Etiele Greque de; Trovão, Mafalda; Machado, Adriana; Carvalho, Bernardo; Carneiro, Mariana; Maia, Inês; Soares, Maria; Duarte, Paulo; Barros, Ana; Pereira, Hugo; Silva, Joana; Varela, JoãoMicroalgae are widely used as food supplements due to their high protein content, essential fatty acids and amino acids as well as carotenoids. The addition of microalgal biomass to food products (e.g., baked confectioneries) is a common strategy to attract novel consumers. However, organoleptic factors such as color, taste and smell can be decisive for the acceptability of foods supplemented with microalgae. The aim of this work was to develop chlorophyll-deficient mutants of Chlorella vulgaris by chemically induced random mutagenesis to obtain biomass with different pigmentations for nutritional applications. Using this strategy, two C. vulgaris mutants with yellow (MT01) and white (MT02) color were successfully isolated, scaled up and characterized. The changes in color of MT01 and MT02 mutant strains were due to an 80 and 99% decrease in their chlorophyll contents, respectively, as compared to the original wild type (WT) strain. Under heterotrophic growth, MT01 showed a growth performance similar to that of the WT, reaching a concentration of 5.84 and 6.06 g L-1, respectively, whereas MT02 displayed slightly lower growth (4.59 g L-1). When grown under a light intensity of 100 μmol m-2 s-1, the pigment content in MT01 increased without compromising growth, while MT02 was not able to grow under this light intensity, a strong indication that it became light-sensitive. The yellow color of MT01 in the dark was mainly due to the presence of the xanthophyll lutein. On the other hand, phytoene was the only carotenoid detected in MT02, which is known to be colorless. Concomitantly, MT02 contained the highest protein content, reaching 48.7% of DW, a 60% increase as compared to the WT. MT01 exhibited a 30% increase when compared to that of the WT, reaching a protein content of 39.5% of DW. Taken together, the results strongly suggest that the partial abrogation of pigment biosynthesis is a factor that might promote higher protein contents in this species. Moreover, because of their higher protein and lower chlorophyll contents, the MT01 and MT02 strains are likely candidates to be feedstocks for the development of novel, innovative food supplements and foods.