Boosya Bunnag

Separation and purification of phycocyanin from Spirulina sp. using a membrane process

The highest purity ratio of phycocyanin extract was obtained when fresh biomass was used as raw material. The crude extract was purified by membrane process using microfiltration and ultrafiltration. Membrane of pore sizes 5 μm, at feed flow rate of 150 mL min(-1), permeate flux of 58.5 L h(-1)m(-2) was selected for coarse filtration and membrane with pore size 0.8/0.2 μm at the flow rate of 100 mL min(-1), permeate flux of 336 L h(-1)m(-2) was selected for fine filtration, giving phycocyanin recovery of 88.6% and 82.9%, respectively. For ultrafiltration, membrane with MWCO at 50 kDa, 69 kPa and 75 mL min(-1) of flow rate with a mean permeate flux 26.8 L h(-1)m(-2) and a retention rate of 99% was found to be optimal. Under these filtration conditions, food grade phycocyanin with the purity around 1.0 containing c-phycocyanin as the major component was obtained.

Role of light and photosynthesis on the acclimation process of the cyanobacteriumSpirulina platensis to salinity stress

The response ofSpirulina platensis cells to salinity stress was studied. Once adapted to the higher osmoticum, photosynthetic parameters such as the maximum rate of photosynthesis under saturating irradiance (Pmax) and the initial slope of the P-I curve (α) are reduced by 15% and 25% in 0.5 M NaCl grown cells, respectively. Salt-adapted cells have a modified biochemical composition; reduced protein and chlorophyll content, and an increased level of carbohydrates. The reduction in the photosynthetic capacity of the salt-adaptedSpirulina cells reflects a lower ability to utilize light energy and results in an increase in the susceptibility of the stressed cells to photoinhibition. This conclusion is supported by the finding that cultures exposed to salt stress show not only a decrease in growth rate (μ), but lose the ability to respond to increased irradiance with an increase in growth. The use of variable fluorescence as a fast and reliable measurement to follow the changes in PSII of salt-stressesSpirulina cells enables following the early events of salinity shock. It indicates that as soon as the cells are exposed to salt, a protection mechanism is induced. This mechanism does not require any protein synthesis and may take place even in the dark, though at somewhat reduced effectiveness. The significance of the result in providing a better understanding of the interaction between two environmental stresses — light and salinity — and their application in the outdoor mass cultivation ofSpirulina are discussed.

Polysaccharide extraction from Spirulina sp. and its antioxidant capacity

To optimize polysaccharide extraction from Spirulina sp., the effect of solid-to-liquid ratio, extraction temperature and time were investigated using Box-Behnken experimental design and response surface methodology. The results showed that extraction temperature and solid-to-liquid ratio had a significant impact on the yield of polysaccharides. A polysaccharides yield of around 8.3% dry weight was obtained under the following optimized conditions: solid-to-liquid ratio of 1:45, temperature of 90°C, and time of 120 min. The polysaccharide extracts contained rhamnose, which accounted for 53% of the total sugars, with a phenolic content of 45 mg GAE/g sample.

Light acclimation and photoinhibition in threeSpirulina platensis (cyanobacteria) isolates

Three isolates ofSpirulina platensis (Norst) Geitler marked BP, P4P and Z19/2 were compared with respect to their response and acclimation capability to high photon flux densities (HPFD). Cultures exposed to HPFD (1500–3500 μmol photon m−2 s−1) exhibited a marked decrease in light-dependent O2 evolution rate. P4P was more sensitive to HPFD than the two other isolates. All three isolates recovered from photoinhibition when placed under low PFD. The BP isolate was able to recover also in the dark but to a lower extent and at a lower rate, while no recovery was observed in the other two isolates under dark conditions. No recovery was observed when protein synthesis was inhibited using chloramphenicol. Cultures grown at 200 μmol photon m−2 s−1 differed from cultures grown at 120 μmol photon m 2 s-1 by their lower maximal photosynthetic rate (Pmax) and higher light saturation (Ik) value, while being more resistant to HPFD stress. The ability ofSpirulina isolates to acclimate and withstand HPFD may provide useful information for the selection of strains useful for outdoor mass cultivation.

Photosynthetic characterization of a mutant of Spirulina platensis

A mutant of Spirulina(Arthrospira) platensis, strain I22,obtained by mutagenesis with ethylmethanesulfonate, was partially defective inthe production of γ-linolenic acid. However, when compared with the wildform, the I22 mutant almost lost its capacity to grow at low temperatures,although at optimal temperature growth was unaffected. Measurement of themutants photosynthetic characteristics, including O2-evolution,Pmaxand light saturation values, revealed significantly lower values than for thewild type, in contrast to the higher content of photosynthetic pigments,chlorophyll and phycocyanin. Whereas the total activity of photosynthesis oftheI22 mutant was 58% lower than that of the wild type, the PS II activity of theI22 mutant was 23% higher. On the other hand, the I22 mutant was 69% lower inPSI activity, and the growth rate of this mutant was limited at high lightintensity. These results indicated that the defect in the PS I complex of theI22 mutant may reduce its ability to utilize light to generate the energy usedin diverse biochemical processes, including fatty acid desaturation.

Enhancement of survival and metamorphosis rates of Penaeus monodon larvae by feeding with the diatom Thalassiosira weissflogii

The purpose of this study was to compare the performance of two species of diatoms, Thalassiosira weissflogii and Chaetoceros gracilis, in the larviculture of the black tiger shrimp Penaeus monodon. Shrimp larvae were fed with either C. gracilis, T. weissflogii, or a combination of the two species of diatoms. The larvae fed solely with T. weissflogii or a combination of the two types of diatom had significantly higher survival rates and faster metamorphosis than those fed solely with C. gracilis. The numbers of diatom cells consumed by larvae during 3-h periods were determined, revealing that larvae consumed significantly higher numbers of C. gracilis than T. weissflogii. However, when the protein, total fatty acid, and polyunsaturated fatty acid content of the two species of diatom are compared, significantly higher amounts of each are found in T. weissflogii. Converting the number of diatom cells consumed into equivalent protein, total fatty acid, eicosopentaenoic acid, and decosahexaenoic acid reveals that larvae fed with T. weissflogii received significantly higher amounts of all the nutrients, compared to those consuming C. gracilis. The results showed an advantage of feeding T. weissflogii to C. gracilis in enhancing survival and metamorphosis in P. monodon larvae.

Productivity of the cyanobacterium Spirulina platensis in cultures using sunlight

The growth kinetics of a vacuolated Spirulina platensis strain BP and a non-vacuolated Spirulina platensis strain 12D in open pond cultures were studied. The changes in the dissolved oxygen concentration of the cultures were parallel to the sunlight intensity profiles during the day. The specific growth rate remained unchanged over a large part of the day, although the growth rate in the early morning varied as a function of cell concentration. The variation in the dark respiration rate during the day was about 30%. The photosynthesis of the cultures was not photoinhibited in the early morning. The degree of photoinhibition increased in the morning to reach a value of 15–24%, depending on the cell concentration and light intensity at noon, and then decreased gradually in the afternoon. The study suggests that the rate limiting step in the growth of Spirulina cultures using sunlight was not at the light harvesting step (photosynthesis), but the rate of uptake of a key substrate, or the activity of a key enzyme in the biochemical pathways.

Effect of extraction temperature on the diffusion coefficient of polysaccharides from Spirulina and the optimal separation method

The extraction temperature had a significant impact on the concentration of polysaccharides derived from solid-liquid extraction of Spirulina. The polysaccharide concentration was significantly higher when the extraction was performed at 90°C than when it was performed at 80, 70, and 50°C. This result is related to the diffusion coefficients of the polysaccharides, which increased from 1.07 × 10−12 at 50°C to 3.02 × 10−12 m2/sec at 90°C. Using the Arrhenius equation, the pre-exponential factor (D0) and the activation energy (Ea) for Spirulina polysaccharide extraction were calculated as 7.958 × 10−9 m2/sec and 24.0 kJ/mol, respectively. Among the methods used for the separation of Spirulina polysaccharides, cetyltrimethylammonium bromide (CTAB, method I) and organic solvent (ethanol, in methods II and III) provided similar yields of polysaccharides. However, the separation of polysaccharides using an ultrafiltration (UF) process (method III) and ethanol precipitation was superior to separation via CTAB or vacuum rotary evaporation (method II). The use of a membrane with a molecular weight cut-off (MWCO) of 30 kDa and an area of 0.01 m2 at a feed pressure of 103 kPa with a mean permeate flux of 39.3 L/m2/h and a retention rate of 95% was optimal for the UF process. The addition of two volumes (v/v) of ethanol, which gave a total polysaccharide content of approximately 4% dry weight, was found to be most suitable for polysaccharide precipitation. The results of a Sepharose 6B column separation showed that the molecular weights of the polysaccharides in fractions I and II were 212 and 12.6 kDa, respectively.

Adoption, Cost and Livelihood Impact of Machinery Services Used in Small-Scale Sugarcane Production in Thailand

A survey was conducted to explore the adoption, cost and livelihood impact of machinery services by small-scale sugarcane farmers at village level in 11 designated areas across Thailand. Distinct variations of those services were found for land preparation with 12 patterns of tillage service being identified. Average total costs of machinery services were between 45 and 65% of the overall production costs. Costs of harvesting and transport, irrigation and land preparation accounted among the highest. Copying behaviour and being under the quota subsystem played a major role in the adoption of machinery services. Tillage and irrigation services were perceived by a majority of farmers as the most important operation affecting their livelihoods, as determined by indicators such as reduced drudgery, meeting timeliness of operations, increased yield and profit, and reduced concerns over dry spells and droughts. However, those once relying on rainwater alone and experiencing difficulty in maintaining good yields placed the mechanized irrigation services at the highest priority. The quality of machinery services for client farmers especially not in the quota system was of concern as inferior quality of the services was reported in all designated areas. Solutions to the problems and policy implications to enhance the livelihood of farmers and creating demand and supply for machinery services have been suggested.

Stepwise extraction of high-value chemicals from Arthrospira (Spirulina) and an economic feasibility study

Highlights • Phycocyanin (8.66%) was the main product from the process of the stepwise extraction.• In addition, 3.55% TFA and 0.72% polysaccharide were coproducts from the Arthrospira residue.• Arthrospira should contain 15% phycocyanin to ensure a positive NPV of investment.