Browsing by Subject "Microalgae"

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High molecular weight λ-carrageenan improves the color stability of phycocyanin by associative interactions
(2022) Buecker, Stephan; Grossmann, Lutz; Loeffler, Myriam; Leeb, Elena; Weiss, Jochen
Phycocyanin is a protein-chromophore structure present in Arthrospira platensis commonly used as a blue-colorant in food. Color losses of phycocyanin can be reduced by electrostatic complexation with λ-carrageenan. The aim of this study was to investigate the effect of molecular weight (MW) of λ-carrageenan on the color stabilization of electrostatic complexes formed with phycocyanin and λ-carrageenan. Samples were heated to 70 or 90°C at pH 3.0 and stored at 25°C for 14 days. The MW of λ-carrageenan was reduced by ultrasound treatments for 15, 30, 60, and 90 min. Prolonged ultrasonication had a pronounced effect on the Mw, which decreased from 2,341 to 228 kDa (0–90 min). Complexes prepared with low MW λ-carrageenan showed greater color changes compared to complexes prepared with high MW λ-carrageenan. The MW had no visible effect on color stability on day 0, but green/yellow shifts were observed during storage and after heating to 70°C. Medium MW showed less color stabilization effects compared to low MW when heated to 70°C. Moreover, for solutions prepared with ultrasonicated λ-carrageenan, significant hue shifts toward green/yellow, and precipitation were observed after a heat treatment at 90°C. In addition, the sizes of the complexes were significantly reduced (646–102 nm) by using ultrasonicated λ-carrageenan, except for the lowest MW λ-carrageenan when heated to 90°C. Overall, these findings demonstrated that decreasing the MW of λC had adverse effects on the color stability of PC:λC complexes heated to 70 and 90°C.
Identification and quantification of tocomonoenol isomers in plants and microalgae and investigation of their metabolism in liver cells
(2022) Montoya Arroyo, Alexander; Frank, Jan
Tocopherols (T), tocomonoenols (T1), and tocotrienols (T3) are tocochromanols, a group of bioactive compounds composed of a chromanol ring and a 16-carbon sidechain with biological functions, such as the protection of lipid membranes from oxidation and the modulation of cellular signaling. T have saturated sidechains, while T1 and T3 have a single or three double bonds in theirs, respectively. The prefixes alpha-, beta-, gamma-, and delta- are assigned based on the number and positions of methyl groups on the chromanol ring. alpha-, beta-, gamma-, and delta-congeners of T1 have been reported, with alpha-T1 being the predominantly identified congener. Two different alpha-T1 isomers are known, 11-alpha-T1, which has been mainly found in land plants, and 12-alpha-T1, which has been mostly detected in marine organisms. However, little is known regarding the occurrence of T1 in photosynthetic organisms and their metabolism in the liver, a strong determinant of bioavailability and bioactivity. The aim of this thesis was to evaluate underutilized plant-based food sources, cyanobacteria, and microalgae as potential sources of T1 and to characterize the uptake and conversion into metabolites of T1 in cultured liver cells in comparison to T and T3. Acrocomia aculeata fruits were analyzed for alpha-T1 due to its phylogenetic relationship with Elaeis spp, the most common source of this congener. No alpha-T1 was detected in oils from endosperm and mesocarp of wild fruits of Acrocomia aculeata from Costa Rica. Aerial parts of the local underutilized leafy vegetable Urtica leptophylla were evaluated as source of T1 due to its agronomical potential and previous reports of T1 in leaves of plants. LC-MS analyses indicated that leaves and flowers of Costa Rican Urtica leptophylla contain minor amounts of alpha-T1 and gamma-T1. Cyanobacteria and microalgae from different species and origins were analyzed as source of alpha-T1 due to their role as primary producers in aquatic ecosystems and the reported presence of 12-alpha-T1 in marine phytoplankton. alpha-T1 in cyanobacteria and microalgae ranged from traces up to 17% of the total tocochromanol content. alpha-T1 concentrations alone were higher than the sum of all four T3. 11-alpha-T1 was the major alpha-T1 isomer in cyanobacteria and microalgae, as determined by GC-MS. Hence, 11-alpha-T1 is a product of biosynthetic pathways even in aquatic organisms. The effect of nitrogen depletion during the cultivation of microalgae on their alpha-T1 content was investigated. Nitrogen depletion did neither significantly affect the relative or absolute content of alpha-T1, despite an increase in tocochromanol content, nor the proportion of 11-alpha-T1/12-alpha-T1 in microalgae. The uptake and conversion into metabolites of 11-alpha-T1 in HepG2 liver cells was compared to those of alpha-T3 and alpha-T. Cellular uptake of alpha-T1 in liver cells was higher than that of alpha-T. 11-alpha-T1, similar to alpha-T, was converted mostly to alpha-carboxymethylhydroxychroman in a time dependent manner, but to lower extend than alpha-T3. The effect of both ring methylation and sidechain saturation on the uptake and metabolism of the alpha- and gamma-congeners of T1, T and T3 was studied in HepG2 cells. gamma-Congeners were metabolized at higher extent than alpha-congeners and metabolite production increased with increasing number of double bonds in the sidechain independently of chromanol ring methylation. In conclusion, alpha-T1 is present with up to 17% of total tocochromanols in cultured microalgae, which thus are an important new source of this congener. gamma-T1 is only a minor tocochromanol in U. leptophylla flowers. 11-alpha-T1, and not 12-alpha-T1, is the major alpha-T1 isomer in cyanobacteria and microalgae and nitrogen depletion of microalgae does not significantly affect alpha-T1 concentration. The metabolic conversion of alpha-T1 into alpha-carboxymethylhydroxychroman in HepG2 cells is similar to that of alpha-T and significantly lower than that of alpha-T3, suggesting that it may be handled by the organism similar to alpha-T. In conclusion, novel potential food sources of alpha-T1 have been identified and, because of similarities with alpha-T, its pharmacokinetics and biological activities warrant further investigation.
Investigations on nutritional characteristics of microalgae with emphasis on ruminants
(2019) Wild, Katharina Judith; Rodehutscord, Markus
The main objective of the present thesis was to systematically determine nutritional characteristics of microalgae and evaluate the suitability of microalgae as feedstuffs, particularly for ruminants. The experiments comprised a comprehensive characterisation of microalgae nutrient profiles with chemical-analytical methods and the determination of extent and dynamics of nutrient utilization using in vitro methods. In order to generate a comprehensive database on nutrient composition of microalgae, 16 commercial microalgae biomasses of four genera (Arthrospira, Chlorella, Nannochloropsis, and Phaeodactylum) were analysed utilizing established methods for food and feed evaluation (Manuscript 1). These investigations included determination of the in vitro crude protein (CP) digestibility for pigs. Nutrient analyses showed a considerable variation particularly in concentrations of proximate nutrients, minerals, and fatty acids, both among and within genera. This variation presumably resulted from varying cultivation conditions and it was concluded that general mean values are not appropriate to characterize microalgae in terms nutrient composition. Manuscript 2 aimed to determine characteristics of the nutritional value of microalgae for ruminants utilizing different in vitro methods. The commercial biomasses included in Manuscript 1 were investigated using the Hohenheim Gas Test method. The investigations comprised the determination of several ruminal fermentation characteristics, of the energy value, and of the protein value. A three-step enzymatic in vitro system was used to estimate intestinal digestibility of ruminally undegraded CP (IDP). Ruminal fermentation of the investigated microalgae biomasses was overall low, which was indicated by an overall low level of production of gas and volatile fatty acids, and a low ruminal CP degradation. As a result of low ruminal fermentation, microalgae biomasses were characterized by high concentrations of ruminally undegradable CP (RUP; 386, 399, 315, and 263 g RUP/kg DM at passage rate of 8 %/h for Arthrospira, Chlorella, Nannochloropsis, and Phaeodactylum, respectively). Thus, microalgae appear to be potential alternative protein sources for high performing animals. However, this was contradicted by low IDP, which was determined for microalgae in the present thesis for the first time (mean values for Arthrospira, Chlorella, Nannochloropsis, and Phaeodactylum were 27, 43, 43, and 40 % of RUP respectively). The variation observed in nutrient profiles was reflected in several nutritional characteristics. A common objective of Manuscript 1 and Manuscript 2 was to investigate whether cell disruption affects nutritional characteristics of microalgae. In Manuscript 1, effects of cell disruption on in vitro CP digestibility for pigs were investigated and in Manuscript 2 several in vitro methods were utilized to investigate effects of cell disruption on the nutritional value of microalgae for ruminants. Mechanical cell disruption with a ball mill enhanced in vitro CP digestibility and ruminal fermentation in most of the samples, presumably by the destruction of cells and hence an increase in nutrient accessibility. Nevertheless, concerning the protein value of microalgae in ruminants, application of mechanical cell disruption cannot not be recommended because it decreased RUP but did not increase IDP so that intestinal digestible RUP was overall decreased by cell disruption. The aim of the third manuscript was to investigate the effects of variable cultivation conditions on nutrient composition and nutritional characteristics for ruminants of the microalgae Chlorella vulgaris. Chlorella vulgaris was cultivated under varying conditions (saturation, nitrogen and CO2 depletion, outdoor cultivation). The obtained biomasses were analysed for their nutrient composition and their nutritional value for ruminants using different in vitro methods. Both, nutrient composition and characteristics of the nutritional value for ruminants were affected by the cultivation process. Nutrient deficient conditions had rather adverse effects in terms of digestibility, protein value, and nutrient productivity. It can be concluded that microalgae have potential as alternative protein source for ruminants. Nevertheless, this potential is contradicted by low IDP, but the findings obtained herein have to be verified in future studies. Furthermore, the results of the present thesis show that nutrient composition and ruminal fermentation characteristics of microalgae vary considerably between and in many cases even within microalgae genera. Thus, to the extent possible, it should be strived for a standardisation of cultivation conditions, in order allow better predictions of nutritional characteristics of microalgae.
Die Mikroalge Phaeodactylum tricornutum : Bioverfügbarkeit, Sicherheit und potenzieller gesundheitlicher Nutzen für die humane Ernährung
(2023) Kopp, Lena Janine; Bischoff, Stephan C.
The dissertation by Lena Kopp investigated the suitability of the microalga Phaeodactylum tricornutum (PT) for human nutrition. PT contains essential nutrients such as the long-chain omega-3 fatty acid eicosapentaenoic acid (EPA), which is otherwise found mainly in fish. In addition, PT contains a high content of other nutrients such as proteins, carotenoids (in particular fucoxanthin), vitamins and β-glucans, which have nutritive and therapeutic potential. Clinical and animal studies have shown that the PT biomass ingestion is safe and has potential health effects, such as anti-inflammatory and prebiotic effects. The results suggest that PT can be used as a food for human nutrition with possible health-promoting effects.
Oral intake of the microalgae Nannochloropsis oceanica, Chlorella vulgaris, or Phaeodactylum tricornutum improves metabolic conditions in hypercaloric-fed mice
(2024) Kopp, Lena; Seethaler, Benjamin; Neumann, Ulrike; Bischoff, Stephan C.
Diet-induced metabolic load is associated with excess body weight and liver steatosis. Here, selected microalgae, known to contain bioactive nutrients, were studied for beneficial metabolic effects in a mouse model of liver steatosis. Adult mice (8 per group) were fed either a Western-style diet (WSD) or a control diet +/ 15 % of the microalgae Chlorella vulgaris (CV), Nannochloropsis oceanica (NO), or Phaeodactylum tricornutum (PT) for 12 weeks. We evaluated liver fat content and liver damage, as well as fecal microbiota and lipopolysaccharide (LPS) translocation. NO supplementation to a WSD reduced the grade of liver steatosis (from 17 % to 4.7 %, p < 0.002), the liver damage score (p < 0.001), and LPS translocation (p < 0.001). PT had similar effects on liver damage score (p < 0.001) and LPS translocation (p < 0.001). CV supplementation reduced LPS translocation (p < 0.001). In conclusion, dietary supplementation of microalgae may be a novel sustainable approach to combat metabolic loads.