Biomass and lipid enhancement in Ankistrodesmus sp. cultured with reused and minimal nutrients media

Microalgae are a promising feedstock for biofuel production. Lipid content in microalgae could be enhanced under nutrient depletion. This work investigated the effect of the nutrient on lipid accumulation in Ankistrodesmus sp. culture. Batch cultures were carried out using fresh BG11 medium, and after the harvest, the medium was reused for the next culture; this method was repeated two times. The maximum lipid productivity of 29.75 mg L^?1 day^?1 was obtained from the culture with the second reuse medium. In continuous cultures, Ankistrodesmus sp. was cultured in both fresh and modified BG11 mediums. The modified BG11 medium was adjusted to resemble the content of the first reuse medium. As a comparison between batch and continuous cultures, it was proven that the productivity in the continuous culture was better than in the batch, where the achievable maximum biomass and lipid were 188.30 and 38.32 mg L^?1 day^?1. The maximum lipid content of 34.22% was obtained from the continuous culture at a dilution rate of 0.08 day^?1, whereas the maximum saturated and unsaturated fatty acid productivities of 79.96 and 104.54 mg L^?1 day^?1 were obtained at a dilution rate of 0.16 day^?1.     

Photoautotrophic high-density cultivation of vegetative cells of Haematococcus pluvialis in airlift bioreactor

This work aimed to investigate the effects of the bioreactor configurations and their design variables on the cultivation of vegetative cells Haematococcus pluvialis to achieve sustainable high cell density. The addition of vitamin B to F1 growth medium could appreciably enhance the final cell density. Employing this medium, the cultivation in the airlift bioreactor was demonstrated to outperform the bubble column at the same operating conditions. Aeration was crucial for a proper growth of the alga in the airlift bioreactor, but it must be maintained at low level to minimize shear stress. The most appropriate aeration velocity (superficial velocity) was at the lower limit of the pump, i.e. 0.4 cm s(-1) and a smaller riser was shown to have positive influence on the cell growth. A 1% CO(2) supplement to the air supply considerably enhanced the growth rate of H. pluvialis and the most suitable light intensity for the growth was at 20 micromol photon m(-2) s(-1). The semi-continuous culture was successfully implemented with the optimal airlift bioreactor design and under optimal conditions the harvest could be performed every four days with the specific growth rate of 0.31 d(-1).     

Isolation and characterization of Dunaliella salina from Thailand

Screening of Dunaliella was performed in four provinces along the coast of the Gulf of Thailand (Chanthaburi, Chon Buri, Chachoengsao and Samut Songkhram) and in Nakhorn Ratchasima province in the north-east. Six clones of D. salina were isolated from salt fields in Samut-Songkhram province. Clone DS91008 produced the highest carotenoid content of 80.3 pg cell^-1, in modified J/1 medium at 30% NaCl under continuous illumination at 270 μmol m^-2 s^-1.     

Inorganic nitrogen control in a novel zero-water exchanged aquaculture system integrated with airlift-submerged fibrous nitrifying biofilters

This work examined the feasibility of applying shrimp diets to establish nitrification on submerged fibrous biofilters. It also investigated the performance of a proposed zero-water exchanged aquaculture system, which integrated growing of aquatic stocks and operation of acclimated biofilters in the same environment. Addition of shrimp diets fully established nitrification within 3 weeks as indicated by continuous increase of nitrate and trivial levels of ammonium and nitrite. A series of batch experiment revealed an average ammonium degradation rate of 24.1 mg N m^?2 day^?1. Zero-water discharged tilapia cultivation could be carried out in the proposed aquaculture system for at least 44 days when daily inorganic loadings increased from 1.24 to 10.78 mg N l^?1 day^?1. The corresponding daily growth rates of tilapia from the proposed aquaculture systems integrated with acclimated biofilters varied from 3.01 to 3.35 g day^?1, which was approximately 7–16% better than numbers from the systems using non-acclimated biofilters.     

Continuous production of diatom Entomoneis sp. in mechanically stirred tank and flat-panel airlift photobioreactors

Continuous production of diatom Entomonies sp. was performed in mechanically stirred tank and flat-panel airlift photobioreactors (FPAP). The maximum specific growth rate of diatom from the batch experiment was 0.98 d^?1. A series of dilution rate and macronutrient concentration adjustments were performed in a stirred tank photobioreactor and found that the dilution rate ranged from 0.7 to 0.8 d^?1 and modified F/2 growth media containing nitrate at 3.09?mg N/L, phosphate at 2.24?mg P/L, and silicate at 11.91?mg Si/L yielded the maximum cell number density. Finally, the continuous cultivation of Entomonies sp. was conducted in FPAP using the optimal conditions determined earlier, resulting in the maximum cell number density of 19.69?×?10⁴ cells/mL, which was approximately 47 and 73% increase from the result using the stirred tank photobioreactor fed with modified and standard F/2 growth media, respectively.     

Photoautotrophic cultivating options of freshwater green microalgal Chlorococcum humicola for biomass and carotenoid production

Photoautotrophic cultivation of Chlorococcum humicola was performed in batch and continuous modes in different cultivating system arrangements to compare biomass and carotenoids’ concentration and their productivities. Batch result from stirred tank and airlift photobioreactors indicated the positive effect of increasing light intensity on growth and carotenoid production, whereas the finding from continuous cultivation indicated that carotenoid enhancement preferred high light intensity and nitrogen-deficient environment. The highest biomass (1.31?±?0.04?g?L^?1) and carotenoid (4.59?±?0.06?mg?L^?1) concentration as well as the highest productivities, 0.46?g?L^?1 d^?1 for biomass and 1.61?mg?L^?1 d^?1 for carotenoids, were obtained when maintaining high light intensity of 10 klx, BG-11 medium and 2% (v/v) CO₂ simultaneously, while the highest carotenoid content (4.84?mg?g^?1) was associated with high light intensity and nitrogen-deficient environment, which was induced by feed-modified BG-11 growth medium containing nitrate 20 folds lower than the original medium. Finally, the cultivating system arranged into smaller stirred tank photobioreactors in series yielded approximately 2.5 folds increase in both biomass and carotenoid productivities relative to using single airlift photobioreactor with equivalent working volume and similar operating condition.     

Enhanced productivity of Chaetoceros calcitrans in airlift photobioreactors

The various modes of cultivation of Chaetoceros calcitrans in airlift photobioreactors (ALPBRs) were examined. The batch system illustrated that the airlift configuration was superior to the bubble column as the airlift supported the circulation of the cell within the system, leading to a better light utilization. The cultivations in both semi-continuous and continuous systems resulted in a high cell productivity, although the steady state cell concentrations in both systems were lower than that obtained from the batch system. The behavior of the large-scale airlift system was not significantly different from the conventional bubble column where the diatom could only be produced at low cell density. Despite this, among all of the systems investigated in this work, the large-scale system gave the highest productivity. The main limiting factor for the large-scale airlift culture was the availability of light. Based on economical analysis, the continuous cultivation in the 2.8L ALPBR with a medium feed rate of 3 mL min(-1) was most attractive where the operation cost could be maintained at a minimum of approx. 7.95 x 10(-4)THBL(-1)h(-1). However, this continuous small-scale system still suffered from relatively low cell productivity (8.10 x 10(4)cellss(-1)).     

Encapsulation of Haematococcus pluvialis using chitosan for astaxanthin stability enhancement

Astaxanthin is receiving commercial interest due to its use as a preferred pigment in aquaculture feeds. Its antioxidant activity is approximately 100 times higher than that of β-tocopherol, and can be used as a potential agent against cancer. Astaxanthin can easily be degraded by thermal or oxidative processes during the manufacture and storage. In this study, astaxanthin and its biological activity were protected against oxidative environmental conditions by encapsulating the homogenized cells in chitosan. Haematococcus pluvialis were formed into beads, which were then coated with 5 layers of chitosan film, resulting in chitosan-algae capsules that have a mean diameter of 0.43 cm and the total film thickness of approximately 100 μm. No significant loss in the amount of astaxanthin content in H. pluvialis was found due to the process of encapsulation. However, approximately 3% loss of antioxidant activity of the H. pluvialis was observed after encapsulation. The results of stability under different storage conditions showed that although encapsulation caused 3% loss of antioxidant activity, the longer term stability of the dried algae biomass, beads, and capsules indicated that encapsulation of H. pluvailis in chitosan film was capable of protecting the algae cells from oxidative stresses.     

Effect of daytime CO2 supplement on productivity and biochemical composition of Scenedesmus armatus under outdoor cultivation

The cultivation of Scenedesmus armatus was carried out under outdoor Thailand climate conditions. The highest actual growth rate occurred at around 9:00 a.m. to 3:00 p.m., with a wide pH range of 6.4 to 11. The supply of CO₂ had slight influence on growth characteristics but did exert some observable effects on nutritional accumulations. Adding CO₂ from 2 to 15% by volume in the aeration (0.2 vvm) caused an increase in lipid and protein from 19.8 to 25.6 and 37.8 to 48.2% w/w, respectively, whereas carbohydrate decreased from 42.5 to 26.2% w/w. Scenedesmus armatus cultivated with 2% CO₂-enriched air provided the highest the average of the average biomass productivity of 91.25 mg L^?1 d^?1, which corresponded to a CO₂ fixation of 165 mg CO₂ L^?1 d^?1 with the average lipid, protein, and carbohydrate productivities of 22.24, 38.34, and 30.67 mg L^?1 d^?1.