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Commercial- and laboratory modified- cationic cassava starches and their composites with magnetic particles were examined for characteristics and separation efficiency. Scanning electron micrographs showed that cationic starch with an increasing degree of substitution (DS) value (0.0180 to 0.91) showed greater clumped polyhedral granules and became markedly enlarged with disintegrated boundaries. Zeta potential analysis revealed that the increase in the DS value in cationic starches resulted in an increase in positive charge. The maximum harvesting efficiency of 92.86 ± 0.46% was achieved when commercial cationic starch with DS 0.040 at 1.0 g L−1 was added to the Chlorella sp. solution. The maximum recovery capacity (10.20 ± 0.16 g DCW g starch−1) was recorded by using commercial cationic starch with DS 0.040 at a lower dosage of 0.1 g L−1. Their composites showed lower separation efficiency than the commercial cationic starches. The results suggest that the commercial cationic cassava starch with 0.040 DS shows great potential as a flocculant for algal separation. This first report of using commercial cationic cassava starch as a flocculant provides a low cost and convenient process to separate algal cells from the culture medium. Moreover, uncontaminated magnetic particle biomass allows for wide range of algal utilization in food and pharmaceutical biotechnologies.

Microalgae are cultured for their useful chemicals, but their development is restricted by the costs and difficulties of harvesting them. New composites, magnetic-cationic cassava starch, were successfully developed to facilitate harvesting. Compared to naked magnetic particles, the composites exhibited higher potential for algal cell recovery. In addition, harvest capacity through the composites was positively related to the degree of cationic substitution (DS) in modified cassava starch. The application of 500 mg L−1 composites with DS value ≥ 0.76 to recover 1 g L−1 Chlorella sp. TISTR8236 (1.67 ± 0.01 g-dry cell weight g-composites−1) from medium broth at pH 9.5 was significantly (p ≤ 0.005) >98% effective. The separation efficiency of this composite for 1 g L−1 algal biomass was evaluated under different composite doses (200 to 800 mg L−1) and pH levels (4 to 10). Ninety-five percent of the algal cell separation efficiency of the magnetic and 0.76 DS cationic starch composite was recorded, when applied to the 300 mg L−1 composite to harvest 1 g L−1 Chlorella sp. TISTR8236 at pH 10 within 2 min. The adsorption isotherm fit the Langmuir model. In addition, desorption of algal cells was conducted by adjustment of the pH of the culture medium. The highest desorption (9.69%) was recorded at pH 12. These composite magnetic-cationic cassava starch particles were shown to be a new adsorption material for algal cell harvesting. This alternative composite for magnetic separation may represent an effective method for saving time and energy in algal industrial processing.

The potential of using akinetes as seed starters for algal cultivation was assessed in Cladophora glomerata. The effects of light intensities and humic acid concentrations on akinete germination, algal growth and biomass production were examined. A C. glomerata akinete that was induced by incubation in 0.1% NaCl under darkness was incubated in Wright's cryptophyte (WC) medium under different light intensities and supplemented humic acid concentrations. Germination and growth were recorded every 24 h for 192 h. Akinetes germinated after 24 h of incubation, and cells started growing after 96 h. Light is required for akinete germination. Light intensity and humic acid concentration significantly affected akinete germination and cell growth (p ≤ 0.001). The incubation of Cladophora akinetes in WC medium with 4 mg L−1 potassium humate under 50 μmol photons m−2 s−1 resulted in high germination and growth. Supplementation with humic acid could extend the growth period and result in an increase in production. In addition, Cladophora germinated from akinetes showed advantages over filaments in terms of attachment to the substratum and expansion of horizontal growth via rhizoid and stolon development. Therefore, akinetes show potential as seed inocula for C. glomerata cultivation, and using akinetes as inocula can be an alternative culture practice for algal production.

The nutritional value, astaxanthin level and population growth of Moina macrocopa fed with Chlorella sp., Saccharomyces cerevisiae and Phaffia rhodozyma in eight treatments (C1: 1 × 105 cells/ml; C2: 1 × 106 cells/ml; S1: 4 × 106 cells/ml; S2: 4 × 107 cells/ml; P1: 4 × 107 cells/ml; P2: 4 × 108 cells/ml; SP1: S + P 4 × 106 : 4 × 107 cells/ml; and SP2: S + P 4 × 106 : 4 × 108 cells/ml) were examined. The results showed that lipid content was significantly different among the treatments but protein and carbohydrate were not. C2 had the highest lipid content (11.83 ± 0.87%) whereas C1 and SP1 had the highest protein (76.26 ± 2.84%) and carbohydrate (14.56 ± 3.04%), respectively. In addition, SP1 had the highest astaxanthin level (0.83 ± 0.19 μg/g) and S1 showed fastest population growth rate (0.81 day−1). This indicated that feeding on S. cerevisiae resulted in high lipid and astaxanthin levels and a concentration of 4 × 106 cells/ml enhanced the population growth of M. macrocopa. Therefore, it could replace or be used as supplementary to Chlorella sp. for cladoceran production in mass cultures.

C-Phycocyanin, a blue-colored and water soluble protein, is a class of phycobiliproteins that are the major light-harvesting pigments of a photosynthetic system in cyanobacteria. C-phycocyanins are utilized in many industries, including as natural colorants in food and cosmetics and as antioxidant compounds. However, the uses of C-phycocyanins have been limited due to their vulnerability to high temperatures. Therefore, the objective of this study was to identify and analyze the C-phycocyanin gene isolated from Thermosynechococcus sp. TUBT-T01, living in a hot spring in Surat Thani province, in the hope that this C-phycocyanin exhibited thermostable properties and that their applications could be expanded over a wide range of industries. In the present study, the polymerase chain reaction of the gene encoding alpha subunits of C-phycocyanin (cpcA) was performed, using primers designed based upon the sequence alignments of cpcA from Thermosynechococcus sp. available in the GenBank database. The putative cpcA, with an approximate size of 500 base pairs, was detected on an agarose gel. The DNA sequencing analysis indicated that the cpcA was 489 base pairs in length, and its nucleotide sequence was 94 % identical to those of thermophilic Thermosynechococcus sp. NK55, T. elongatus BP-1, and Synechococcus vulcanus. The deduced amino acid sequence was very similar to those of Thermosynechococcus sp. NK55, T. elongatus BP-1, and S. vulcanus. The data derived from the homologous model revealed that the presence of Asp28, Lys32, and Ser72 in the alpha subunit of C-phycocyanin from Thermosynechococcus sp. TUBT-T01 could provide the high thermostability property of this protein.

The effects of cyanobacteria and chemical fertilizer on growths and yields of rice (Oryza sativa L.) cv. Pathum Thani 1 were studied in pot trials. Nine treatments were set up without cyanobacteria and fertilizer (control), inoculated with cyanobacteria Nostoc carneum TUBT04 (T1), inoculated with Nostoc commune TUBT05 (T2), and inoculated with combination of N. carneum TUBT04 and N. commune TUBT05 (T3), full dose of recommended use of fertilizer (T4), half dose of recommended use of the fertilizer (T5), half dose of fertilizer combined with N. carneum TUBT04 (T6), half dose of fertilizer combined with N. commune TUBT05 (T7), and half dose of fertilizer combined with N. carneum TUBT04 plus N. commune TUBT05 (T8). Each treatment divides into five replications. Growth parameters including length and fresh and dry weights of shoot and root were measured in the seedlings. The number of spikes per plant and the amount and weight of rice grains per spike were measured after harvesting. The supplement with cyanobacteria promoted rice seedling growth and yield compared to the control treatment. Inoculation with cyanobacteria showed significant increase in root length (p = 0.41). In addition, the combined biofertilizer with a half of the recommended dose of chemical fertilizer significantly enhanced rice production including total number and weight of grain per spike and a total weight of 100 grains (p < 0.001). Therefore, using a half dose of chemical fertilizer with cyanobacteria is suggested to decrease rice production cost of farmers without any effects on rice quantity and quality.

Algae has long been used as a food and a potential source of valuable and bioactive compounds due to residues left after the extraction process. Discovery of an alternative approach to the residues contributes to commercial feasibility in algae biorefinery. This study aimed to examine the cellulose composition in macroalgae. The physiochemical characteristics of cellulose and its potential use as a reinforcement to polyurethane (PU) foam were investigated. A green filamentous freshwater algal biomass composed of Cladophora sp. and Microspora sp. was treated via alkalization. The treated algae was use as a filler agent to synthesize PU-composite foams. Morphological, chemical, mechanical, physiochemical and viscoelastic properties of cellulose and PU-composite foam were investigated through field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) compressive tests, and dynamic mechanical analysis (DMA). A cellulose yield of 37.2% was obtained from Kai algae via alkalization and the crystallinity index was 63.6%. The use of algae and algal cellulose to synthesize PU-composites resulted in foam density increase, while the compressive modulus decreased. The addition of algal cellulose as filler in PU foam significantly reduced the cell size of foam. Using algae at 0.5% (w/v) and algal cellulose at 1.0% (w/v) as filler in PU-composites increased stiffness at 25–50 °C and transition temperature and decreased loss modulus. These results indicated that algae and algal cellulose added during PU-composite foam production may be integrated into the foam structure and result in more open cells and softer foam. The PU-composite showed greater shock absorbent capacity than PU foam. The results provided a new alternative approach in algal cell residue utilization in terms of material, which could be useful for the packaging industry.

C-phycocyanin was extracted from Nostoc commune TUBT05 and Oscillatoria okeni TISTR8549 using freezing and thawing and pulsed electric field treatments. The results confirmed that freezing and thawing can be used to extract c-phycocyanin from both cyanobacterial strains, whereas pulsed electric field treatment can be used only with N. commune, whose cell structure allows extraction by this technology. The number of freeze/thaw cycles, the extraction solution used and the number of electric pulses had statistically significant influences on c-phycocyanin concentration, purity, yield and the total protein content in the crude extracts (p ≤ 0.005). Exposure of N. commune to three cycles of freeze/thaw in sodium-phosphate buffer yielded the highest c-phycocyanin content, purity, and yield. The results suggest that careful selection of both the number of freeze/thaw cycles and the extraction solution is required to ensure high productivity. Transmission electron microscopy micrographs confirmed that the cell wall structure and organization of the thylakoid were different in the two species, requiring a significantly different number of freeze/thaw cycles and pulse applications for optimal c-phycocyanin extraction. Both cyanobacterial strains were shown to be potential alternative strains for c-phycocyanin production. However, further work is needed to improve c-phycocyanin concentration and purity. We suggest that this will require refinement of the cultivation conditions and improved purification processes.

Science & Technology Asia, 22, 3

During an ongoing study of the rotifer diversity in Thai peat swamps, several new or rare species were found. We here report on one new species, Lecane kunthuleensis n.sp., from a canal in Kun Thu Lee peat swamp, and on three rare species: Paracolurella aemula (Myers, 1934) and Lecane junki Koste, 1975 from Kra Jood peat swamp (Suratthanee province), and Lepadella punctata Wulfert, 1939 from To-Daeng peat swamp (Narathiwas province).

We studied the rotifer fauna of one of the most pristine peat-swamps in the Southern Thai province of Narathiwas, To Daeng peat swamp. The samples yielded a total of sixty-seven rotifer species. Of these, three -Keratella mixta (Oparina-Charitonova), Lecane enowi Segers & Mertens and Monommata dentata Wulfert- are new to the Oriental region and the Thai fauna, one, Keratella taksinensis n. sp., is new to science. The fauna consists mainly of cosmopolitan (sensu lato) species, complemented by some Paleotropical and endemic taxa, and is dominated by littoral-benthonic taxa, especially Lecane and, to a lesser extent, Lepadella.

The Rotifera from four peat-swamps in the provinces Suratthanee (Kra-Jood and Kun-Thu-Lee peat-swamps), Nakhonsri-thammarat (Khuan-Kreng peat-swamp) and Yala (Lan-Kway peat-swamp) in southern Thailand were examined by the study of qualitative samples collected on three occasions during July, October and November, 1998. A total of 96 species was identified, seventeen of which are new to the Thai rotifer fauna. The most diverse genera were Lecane (40.6%), followed by Lepadella (8.3%) and Trichocerca (7.3%). The most diverse rotifer fauna was found in Kra-Jood peat-swamp (61 species), followed by Kun-Thu-Lee (57 species), Lan-Kway (41 species) and Khuan-Kreng (24 species) peat-swamps, respectively.