Algal biomass and its commercial utilisation

Algal biomass is a source of high value products worth over A$100 x 10 6 per annum. Red and brown seaweeds yield the phycocolloids, which are used as gelling, viscosity and clarifying agents in the food, cosmetic and pharmaceutical industries. Microalgal products in the health food market include Spirulina and Chlorella powder and tablets. The blue phycocyanin pigment extracted from Spirulina is used as a food colouring, and P-carotene extracted from Dunaliella salina, is sold as a yellow food colouring, and for its provitamin A and anti-oxidant properties in nutritional supplements. Development of new intensive culture systems is expected to widen the range of commercial algal products in the future

The ecology of Dunaliella salina (Chlorophyceae, Volvocales): Effect of environmental conditions on aplanospore formation

The conditions leading to aplanospore formation in the green halophilic flagellate, Dunaliella salina (Dunal) Teodoresco, were studied using mixed cultures established from field collected samples. Aplanospore formation generally requires reduced salinity, (at salinities > 20% w/v NaCl aplanospores are rarely formed), nitrogen depletion and the presence of sulphate. Cool temperatures and short daylength may also promote spore formation, whereas pH and irradiance have no effect. Aplanospore formation takes place once the culture has reached stationary phase and, in such cultures, up to 36% of the total cells present can be aplanospores, although percentages of spores of less than 5% are most common. The only exceptions to this are high-phosphate cultures where aplanospore formation occurs early in the growth cycle and then ceases. However, not all cultures are competent to form aplanospores, and some mixed or unialgal cultures never formed aplanospores under conditions identical to those where aplanospore formation was observed in others. The factor(s) leading to competency are not known. Unlike free-living cells of D. salina, the aplanospores contain the ketocarotenoid, canthaxanthin

Rapid Mass Movement of Chloroplasts during Segment Formation of the Calcifying Siphonalean Green Alga, Halimeda macroloba

is abundant on coral reefs and is important in the production of calcium carbonate sediments. The process by which new green segments are formed over-night is revealed here for the first time. indicated that the movement process is dependent on both microtubules and microfilaments.This unusual process involves the mass movement of chloroplasts at a high rate into new segments during the night and rapid calcification on the following day and may be an adaptation to minimise the impact of herbivorous activity

Nannochloropsis oceanica cultivation in pilot-scale raceway ponds—from design to cultivation

Raceways ponds are the microalgal production systems most commonly used at industrial scale. In this work, two di erent raceway configurations were tested under the same processing conditions to compare their performance on the production of Nannochloropsis oceanica. Biomass productivity, biochemical composition of the produced biomass, and power requirements to operate those reactors were evaluated. Water depths of 0.20 and 0.13 m, and culture circulation velocities of 0.30 and 0.15 m s1 were tested. A standard configuration, which had a full channel width paddlewheel, proved to be the most energy e cient, consuming less than half of the energy required by a modified configuration (had a half channel width paddlewheel). The later showed to have slightly higher productivity, not enough to o set the large di erence in energetic consumption. Higher flow velocity (0.30 m s1) led to a 1.7 g m2 d1 improvement of biomass productivity of the system, but it increased the energy consumption twice as compared to the 0.15 m s1 flow velocity. The latter velocity showed to be the most productive in lipids. A water depth of 0.20 m was the most suitable option tested to cultivate microalgae, since it allowed a 54% energy saving. Therefore, a standard raceway pond using a flow velocity of 0.3 m s1 with a 0.20 m water depth was the most e cient system for microalgal cultivation. Conversely, a flow velocity of 0.15 m s1 was the most suitable to produce lipids.Portugal 2020 Program (POCI-01-0247-FEDER-035234; LISBOA-01-0247-FEDER-035234; ALG-01-0247-FEDER-035234)info:eu-repo/semantics/publishedVersio

A rapid and inexpensive method for surface sterilisation of Ecklonia radiata (Phaeophyta) for tissue culture

Sections of the thallus of the brown alga Ecklonia radiata (C. Ag.) J. Ag. were surface sterilised for tissue culture by dipping in 70% ethanol for 30 s, followed by sterile deionised water for 30 min. A high percentage of aseptic viable explants could be obtained using this treatment, and growth in vitro was initiated

Growth of microalgae on undiluted anaerobic digestate of piggery effluent with high ammonium concentrations

Anaerobic digestate of piggery effluent (ADPE) is extremely high in ammonia toxic to many microorganisms. Bioprospecting and nutrient enrichment of several freshwater and wastewater samples combined and further acclimation resulted in a mixed culture containing at least three microalgae species capable of growing on undiluted ADPE. Outdoor growth of the mixed culture using raceway ponds showed potential for up to 63.7 ± 12.1 mg N-NH4 + L −1 d −1 ammonium removal from the ADPE. The microalgal consortium was dominated by Chlorella sp. and was stable at between 800 and 1600 mg N-NH4 + L −1. Regulation of CO2 addition to the ponds to maintain a pH of 8 increased chlorophyll content of the microalgal consortium. Average microalgal biomass productivity of 800 mg N-NH4 + L −1 culture conditions during five weeks semicontinuous growth was 18.5 mg ash-free dry weight L −1 d −1. Doubling the ammonium concentration from 800 to 1600 mg N-NH4 + L −1 resulted in a 21% reduction of productivity, however the culture grown at 1600 mg N-NH4 + L −1 with the addition of CO2 by keeping pH at pH = 8 led to a 17% increase in biomass productivity

Tissue culture of brown seaweed

The harvesting of macrophyte algae (seaweeds) is well established and on a world-wide scale more than 180,000 tonnes dry weight of algae such as the phaeophytes Laminaria, Undaria,Sargassum and Macrocystis, the red algae Eucheuma, Gracilaria and Porphyra, and the green algae Ulva, Monostroma and Caulerpa are harvested annually. Much of this algal biomass comes from farmed rather than wild species. The red and brown algae are the source of the phycocolloids agar, alginate, agarose and carrageenan which are of fundamental importance to the development of biotechnology; i.e. for the culture of microorganisms (agar), for the separation of biomolecules (alginate and agarose) and for the production of food products (agar, carrageenan, alginate). The successful large-scale cultivation of these algae requires, amongst other things, the ability to select fast growing and disease resistant strains which produce large quantities of the desired phycocolloid. To this purpose classical plant breeding programs are being carried out, however these are slow and the production of superior cultivars takes much time and effort (Van der Meer 1988). In recent years there has therefore been much interest in developing protoplast and tissue culture systems which would allow more rapid selection and propagation of suitable cell lines, the possibility of producing hybrids by cell fusion and new strains by genetic engineering (Polne-Fuller and Gibor 1987b, Le Gallet al. 1990). Work in our laboratory has concentrated mainly on the brown algal genera Ecklonia and Cystophora. Ecklonia was chosen because it is easily obtained and is a potential source of alginate, and Cystophora, a genus endemic to Australia and New Zealand, because previous studies indicated that this genus appears to be a good source of tocopherols and tocotrienols (Gregson et al. 1977, Kazlauskas et al. 1981, unpubl. results). The tocopherols are of interest and also provide a convenient model for the study of the production of secondary metabolites in algal tissue culture. In this paper we describe some of our findings on the tissue culture of these species and on their tocopherol content

Periodic CO2 Dosing Strategy for Dunaliella salina Batch Culture

A periodic CO2 dosing strategy for D. salina 19/30 batch culture is proposed. A model of periodic CO2 dosing including dosing time calculation, dosing interval estimation and final chlorophyll yield prediction was established. In experiments, 5% CO2/95% N2 gas was periodically dosed into D. salina culture. Two different gas dosing flow rates were tested. The corresponding dosing time for each flow rate was estimated via the model (10 min·d−1 for 0.7 L·min−1 and 36 min·d−1 for 0.3 L·min−1). Daily pH measurements showed that the pH of these cultures dosed periodically was always kept between 7.5 and 9.5, which highlights that periodic gas supply can maintain a suitable range of pH for microalgal growth without expensive buffers. Notably the culture dosed for set daily intervals was seen to have similar growth to the culture supplied constantly, but with much higher CO2 capture efficiency (11%–18%) compared to continuous dosing (0.25%). It shows great potential for using periodic gas supply to reduce cost, wasted gas and energy use