Isochrysis Galbana T-Iso Research Articles

Functional and Bioactive Properties of Protein Extracts Generated from Spirulina platensis and Isochrysis galbana T-Iso

There is growing consumer demand for food products derived from microalgae, driven largely by the perceived health benefits associated with them. The functional and bioactive potential of proteins isolated from two microalgae—Spirulina sp. and Isochrysis galbana T-Iso—were determined. The results obtained show the potential of microalgal protein extracts for use in the beverage industry, based on solubility values and other functional characteristics, including water and oil holding capacities, foaming, emulsifying activities and stabilities, water activities, solubility and pH. The solubility of algal proteins was pH-dependent, and they were largely insoluble at pH values between 2 and 11. However, the proteins were increasingly soluble at a pH of 12, and they have potential use in formulating foods with higher viscosities or gels, where they could act as fillers to strengthen networks. Compared with whey and flaxseed proteins, the Spirulina sp. protein extract had a superior oil-holding capacity (OHC). The OHC is important in developing texture in food products such as meats. Overall, better foam stability was observed for both Spirulina sp. and Isochrysis sp. soluble protein extracts, compared with flaxseed protein at pH values from 2 to 10 over a period of 120 min. The foam capacity and stability increase the physical properties of foods. However, the emulsion activity and stability values for soluble algal protein extracts were less than the values observed for flaxseed and whey proteins. Algal proteins would not be suitable for use in creaming and food processing involving flocculation. In addition, algal protein extracts inhibited Angiotensin-converting enzyme-I (ACE-I) and renin, and they have potential for use in functional food ingredient applications to maintain heart health and also to act as meat substitutes.

Rapid detection and quantification of haptophyte alkenones by Fourier transform infrared spectroscopy (FTIR)

Several haptophyte algae produce unique neutral long-chain (C37C40) ketones (alkenones) with two to four trans-carbon-carbon double (CC) bonds and a keto-group. These molecules are of great biological interest and may have substantial commercial relevance as biofuel sources. Unfortunately, their detection and quantification, involving extraction from cells with organic solvents and fractionation of lipids through columns, are rather cumbersome. Hence, we developed a method for the rapid and reliable quantification of alkenones in intact cells using Fourier transform infrared spectroscopy (FTIR). The method is based on the absorption band at 962.5cm−1, which corresponds to a trans-CC bond that is unequivocally attributable to alkenones. This peak was exclusively observed in alkenone-producing haptophytes such as Emiliania huxleyi NIES-837, Emiliania huxleyi CCMP 2090, Tisochrysis lutea (former Isochrysis galbana T-iso), Tisochrysis lutea CCMP 463, and Chrysotila lamellosa CCMP 1307, as well as in appropriate standards. We compared our FTIR method with a typical GC analysis method. The alkenone quantity determined by these two methods showed similar values. Nevertheless, the FTIR method developed in this study does not require complex extraction procedures and is therefore a much easier and rapid quantification method. This FTIR method can also be used for the screening of strains and the optimization of culture conditions for alkenone production.

Laboratory Culture of Zebra ( Dreissena polymorpha) and Quagga ( D. bugensis) Mussel Larvae Using Estuarine Algae

Zebra ( Dreissena polymorpha) and quagga mussel (D. bugensis) larvae were reared through and beyond metamorphosis in the laboratory on diets of the estuarine algae, Isochrysis galbana T-Iso and Pavlova ( = Monochrysis) lutheri. Larvae were successfully spawned and raised in the laboratory for over 1 year with routine survival to settlement. Some adult males reared from an August 1994 spawn reached sexual maturity with active sperm by April 1995. Diets of dried Chlorella sp. and Synecococchus sp. were unable to support larvae. Settlement of pediveligers at 22°C occurred at ≈ 21 days for zebra mussel and 32 days for quagga mussels. Saturated fatty acids predominated in I. galbana and P. lutheri, whereas polyunsaturated fatty acids (PUFAs) predominated in Chlorella sp. The process to culture dreissenid larvae in the laboratory is very labor-intensive and requires continuous culture of live algae maintained in log growth phase. Larvae are fed every other day at a density of 2 × 10 5 cells mL −1 for the first week, and then daily densities of 3–5 × 10 5 cells mL −1 thereafter. Water quality is critical. Larvae and juveniles should be stocked at densities of ≈ l mL −1 and the water must be changed at least 3× wk −1 in static cultures. Water must be changed at least weekly in tanks holding adult brood stock. Methods of controlling protozoan and rotifer infestation of cultures are also important for successful culture.

Determination of optimal thermal conditions for growth of clam ( Venerupis pullastra) seed

The energy budget of Venerupis pullastra clam seed (3 mm) fed the microalga, Isochrysis galbana T-ISO, was calculated after acclimation at 10, 15, 20 and 25°C. Physiological measurements included ingestion rate, absorption efficiency, oxygen consumption and ammonia excretion. The effect of temperature on these rates was described. Ingestion rate was directly related to temperature up to a maximum at 20°C. Further temperature increase caused a slight decrease in ingestion. Absorption efficiency was not significantly influenced by the temperature, although maximum mean values were also found at 20°C. Both respiration and ammonia excretion rates were directly related to temperature over the whole experimental range, reaching their maxima at 25°C. For all the physiological rates measured the higher slopes in the rate/temperature lines occurred in the medium range of temperatures (15–20°C). The scope for growth (SFG) was positive at all temperatures and maximum at 20°C, chiefly as a consequence of the enhanced ingestion rate which offset the concomitant elevation in metabolic rates. Both gross and net growth efficiencies are also expected to be maximum at 20°C, which is, therefore, the thermal optimum for this species under the experimental conditions applied in our study. An acclimation strategy for this low-shore species within the range of thermal variation in its natural environment (10–20°C), maximizing SFG at high temperatures by enhancing ingestion rate, despite increased metabolic costs, is proposed.