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Cyanobacterial ToxinsAn important quality control issue surrounding production ofcyanobacteria is

the possibility of inadvertently harvesting other cyanobacteria containing cyanotoxins.

This is a risk when harvesting algae from natural bodies of water containing mixed

populations of phytoplankton, but is unlikely to be a problem with the tightly

controlledArthrospiraglatensis monocultures utilized by the notifiers. Nevertheless,

because certain cyanobacterial and algal toxins are capable of causing widespreadpoisoning of animals and humans (Carmichael 1994), the notifiers take the issue very

seriously.

In 1995-96, a group of leading microalgae and cyanobacteria producers

including Cyanotech Corporation and Earthrise Nutritionals, Inc. sponsored research

conducted by phytoplankton toxicologists. The result was a Technical Booklet for the

Microalgae Biomass Industry as a guide to the use of a very sensitive enzyme linked

immunosorbant assay (ELISA) and a protein phosphate inhibition assay (PPIA) for the

detection of toxic microcystins and nodularins. These methods can detect, monitor

and control cyanotoxins, so producers can assure a safe, nutritious product for human

and animal food supplements (An and Carmichael 1996).

Spirulina is periodically assayed for microcystin and nodularin toxins by ELISA

analysis using in-house testing as well as independent testing at Wright StateUniversity, Dayton, OH. Cyanotech Corporation and Earthrise Nutritionals, Inc. have

never had any detectable amount of microcystin or nodularin toxins in their Spirulina

products.

The culture of spirulina is practised in different media, especially inorganic and decomposed organic

nutrients. Different types of spirulina were cultured to evaluate growth and biochemistry under similar

controlled conditions (Bhattacharya and Shivaprakash, 2005). They cultured three species of Spirulina

viz. Spirulina platensis, S. laxissima and S. lonar. Of the three species S. platensis showed highest growth

rate,biomass, pigment concentration and low intracellular phenolics. The results indicate that S. platensis

reached highest growth in shortest doubling time and the importance of strain selection for large-scale

cultivation. Sanchez-Luna et al. (2004) found that the intermittent addition of urea in the autotrophic

culture ofSpirulina platensis yielded similar results to those obtained by the continuous feeding. Theyfurther concluded that the operation mode of using urea intermittently would be preferable to reduce the

production costs of this cyanobacterium in large-scale facilities.

Figure 2: Spirulina platensis culture in digested sago waste in tankMini high rate algal Tank, Institute of Post-graduate Studies & Research, University of Malaya, Kuala

Lumpur, Malaysia (photo courtesy: S.M. Phang).

Faintuch, Sato and Aguarone (1991) also studied the influence of the nutritional sources on the growth

rate of cyanobacteria. They reported that there is very significant influence of mixtures of defined

proportions of KNO3, urea and ammonia-N on the growth ofSpirulina maxima. The most favourable

growth rates of S. platensis occurred in the presence of 2.57 g/litre KNO3 with growth rate of 0.30.4/day.

Chang et al. (1999) studied the possibility of using nitrifying bacteria for the fulfillment of nitrogen

fertilizer in spirulina mass culture. They first adapted the nitrifying bacteria with pH 8

10, 0.6

2.2percent salt and 612 mg/litre of NaHCO3 in the culture solution. They found that the concentration of

NO3-N reached over 20 mg/litre after the nitrifying bacteria was inoculated in the spirulina culture

solution and then incubated for 6 days at 2535 C

In 1981 the FAO documented the possibilities of blue-green algae replacing chemical fertilizers and

rebuilding the structure of depleted soils (FAO, 1981). In India, blue-green algae are grown in shallow

earthen ponds. When the water evaporates, the dried algae are scooped up and sold to rice farmers. This

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natural nitrogen source is only one-third the cost of chemical fertilizer and it increases annual rice yield in

India by an average of 22 percent. Where chemical fertilizers are not used, algae give the same benefit as

25 to 30 kg of chemical nitrogen fertilizer per acre. Where chemicals are used, algae use allows the

reduction of an equivalent amount of inorganic fertilizer. The use of spirulina-based fertilizers is impeded

by the low cost, ready availability and preferred use of inorganic fertilizers.

Spirulina used in combination with other fertilizers gave good yield of tomato (Zeenat, Sharma and Rizvi,

1990). During the study, the N2-fixing cyanobacterium,Aulosira fertilissima, the non N2-fixingcyanobacterium, Spirulina platensis, and the chemical fertilizer, diammonium phosphate (DAP) were

applied in various combinations to the tomato seedlings in pots four times at seven day interval. Highest

plant fresh weight (290 g/plant), number of leaves (127/plant), number of flowers (29/plant), number of

fruits (37/plant) and fresh weight of fruits (71 g/plant) were achieved with the application of 2.25 g

Aulosira + 2.25 g Spirulina + 0.50 g DAP in each pot. This result represented a 522 percent increase in

number of fruits and a 977 percent increase in yield over the control. Cyanobacteria and DAP did not

show any significant increase in yield when applied alone. The use of biological nitrogen is more

beneficial than inorganic nitrogen as, apart from supplying the much needed nitrogen, and they release

carbon components and other nutrients, which enhance plant growth (Banerjee and Deb, 1996). Spirulina

contains 10 percent N w/w (high percentage), and other macro- and micro-nutrients which are slowly

released under normal soil conditions, and increases fertility.