Photosynthesis and biochemical characterization of the green alga Chlamydopodium fusiforme (Chlorophyta) grown in a thin-layer cascade.

Photosynthesis, growth and biochemical composition of the biomass of the freshwater microalga Chlamydopodium fusiforme cultures outdoors in a thin-layer cascade were investigated. Gross oxygen production measured off-line in samples taken from the outdoor cultures was correlated with the electron transport rate estimated from chlorophyll a fluorescence measurements. According to photosynthesis measurements, a mean of 38.9 ± 10.3 mol of photons were required to release one mole of O2, which is 4.86 times higher than the theoretical value (8 photons per 1 O2). In contrast, according to the fluorescence measurements, a mean of 11.7 ± 0.74 mol of photons were required to release 1 mol of O2. These findings indicate that fluorescence-based photosynthesis rates may not be fully replace oxygen measurements to evaluate the performance of an outdoor culture. Daily gross biomass productivity was 0.3 g DW L-1 day-1 consistently for 4 days. Biomass productivity was strongly affected by the suboptimal concentration at which the culture was operated and by the respiration rate, as the substantial volume of culture was kept in the dark (about 45% of the total volume). As the cells were exposed to excessive light, the photosynthetic activity was mainly directed to the synthesis of carbohydrates in the biomass. In the morning, carbohydrate content decreased because of the dark respiration. Per contra, protein content in the biomass was lower at the end of the day and higher in the morning due to carbohydrate consumption by respiration. The data gathered in these trials are important for the future exploitation of Chlamydopodium fusiforme as a potential novel species in the field of microalgae for the production of bio-based compounds.

Selenium Incorporation to Amino Acids in Chlorella Cultures Grown in Phototrophic and Heterotrophic Regimes.

Microalgae accumulate bioavailable selenium-containing amino acids (Se-AAs), and these are useful as a food supplement. While this accumulation has been studied in phototrophic algal cultures, little data exists for heterotrophic cultures. We have determined the Se-AAs content, selenium/sulfur (Se/S) substitution rates, and overall Se accumulation balance in photo- and heterotrophic Chlorella cultures. Laboratory trials revealed that heterotrophic cultures tolerate Se doses ∼8-fold higher compared to phototrophic cultures, resulting in a ∼2-3-fold higher Se-AAs content. In large-scale experiments, both cultivation regimes provided comparable Se-AAs content. Outdoor phototrophic cultures accumulated up to 400 µg g-1 of total Se-AAs and exhibited a high level of Se/S substitution (5-10%) with 30-60% organic/total Se embedded in the biomass. A slightly higher content of Se-AAs and ratio of Se/S substitution was obtained for a heterotrophic culture in pilot-scale fermentors. The data presented here shows that heterotrophic Chlorella cultures provide an alternative for Se-enriched biomass production and provides information on Se-AAs content and speciation in different cultivation regimes.

Cultivation of Chlorella protothecoides under different growth modes and its utilisation in oil/water emulsions.

Microalgae can be incorporated in different bio-based products; however, the green colour is a barrier for a successful integration. This study aims to overcome this barrier by growing microalgae in different cultivation modes. Mixotrophic cultivation of Chlorella protothecoides resulted in the highest biomass production after 5 days (5.56 ±â€¯0.09 g/L), followed by heterotrophic and photoautotrophic cultivation (4.33 ±â€¯0.15 and 1.80 ±â€¯0.05 g/L, respectively). Mixotrophically and heterotrophically produced biomass presented a reduced greenish colouration compared to photoautotrophically produced biomass. Chlorophyll content resulted in 1.46 ±â€¯0.21 and 0.95 ±â€¯0.28 mg/g dry weight (DW) in mixotrophic and heterotrophic cultures, respectively, and 25.98 ±â€¯1.28 mg/g DW in photoautotrophic cultures. In contrast, the fraction of carotenoids in the total pigments was much higher. With the whole microalgae fractions after cell disruption as ingredients, stable emulsions containing 50% oil could be produced. No syneresis with serum separation was observed 24 h after preparation.

Trends in Microalgae Incorporation Into Innovative Food Products With Potential Health Benefits.

Microalgae have demonstrated potential to meet the population's need for a more sustainable food supply, specifically with respect to protein demand. These promising protein sources present several advantages over other currently used raw materials from an environmental point of view. Additionally, one of the main characteristics of microalgae is the production of bioactive compounds with potential benefits for human health. Microalgae exploitation as a source of protein (bulk protein) and other valuable products within the food industry still presents some drawbacks, mainly because of the underdeveloped technologies and processes currently available for microalgae processing. The systematic improvement of the technology readiness level (TRL) could help change the current situation if applied to microalgae cultivation and processing. High maturity in microalgae cultivation and processing technologies also requires improvement of the economy of scale and investment of resources in new facilities and research. Antioxidative, antihypertensive, immunomodulatory, anticancerogenic, hepato-protective, and anticoagulant activities have been attributed to some microalgae-derived compounds such as peptides. Nevertheless, research on this topic is scarce and the evidence on potential health benefits is not strong. In the last years, the possibility of using microalgae-derived compounds for innovative functional food products has become of great interest, but the literature available mainly focuses more on the addition of the whole cells or some compound already available on the market. This review describes the status of utilising microalgae as an ingredient in innovative food products with potential health benefits.