Effective cultivation conditions and safety evaluation of filamentous cyanobacteria producing phycocyanins with antiglycation activities.

We investigated suitable culture conditions for the production of the blue pigment phycocyanin (PC) from the unique filamentous cyanobacteria Pseudanabaena sp. ABRG5-3 and Limnothrix sp. SK1-2-1. White, green, or red LED irradiation at 30 µmol photons/m2/s was effective for phycocyanin production when compared with Arthrospira platensis (Spirulina) sp. NIES-39, which is generally grown under high light irradiation. To investigate the safety of the cyanobacteria, ABRG5-3 cells were subjected to Ames (reverse mutation) tests and single oral-dose rat studies, which revealed non-mutagenic and non-toxic properties. When three purified phycocyanins (abPC, skPC, and spPC) were subjected to agarose gel electrophoresis, they showed different mobility, indicating that each phycocyanin has unique properties. abPC exhibited strong antiglycation activities as novel function.

Efficient pH and dissolved CO2 conditions for indoor and outdoor cultures of green alga Parachlorella.

Efficient pH and dissolved CO2 conditions for indoor (50-450 mL scale) and outdoor (100-500 L scale) culture of a green alga BX1.5 strain that can produce useful intracellular lipids and extracellular polysaccharides were investigated for the first time in Parachlorella sp. The cultures harvested under 26 different conditions were analysed for pH, dissolved CO2 concentration, and the biomass of extracellular polysaccharides. The BX1.5 strain could thrive in a wide range of initial medium pH ranging from 3 to 11 and produced valuable lipids such as C16:0, C18:2, and C18:3 under indoor and outdoor culture conditions when supplied with 2.0% dissolved CO2. Particularly, the acidic BG11 medium effectively increased the biomass of extracellular polysaccharides during short-term outdoor cultivation. The BG11 liquid medium also led to extracellular polysaccharide production, independent of acidity and alkalinity, proportional to the increase in total sugars derived from cells supplied with high CO2 concentrations. These results suggest Parachlorella as a promising strain for indoor and outdoor cultivation to produce valuable materials.

Development of a method for phycocyanin recovery from filamentous cyanobacteria and evaluation of its stability and antioxidant capacity.

BACKGROUND: Most commercial phycocyanins are extracted from a filamentous cyanobacterium, Arthrospira (Spirulina) platensis. Owing to the expenses of culture and complexities of the physical and chemical methods of phycocyanin purification, a more effective and simple method is required. RESULTS: We developed a new method for efficiently recovering the blue pigment protein, phycocyanin, from unique filamentous cyanobacteria, Pseudanabaena sp. ABRG5-3 and Limnothrix sp. SK1-2-1. The cells were cultivated in economy medium BG11 and lysed by adding water in a 1:16 ratio of wet cells to water. After extraction and purification, 28-30% dry cell weight of phycocyanin was obtained and its purity was confirmed. The stabilities of the phycocyanins at different pH in the presence of high temperature and light conditions and their antioxidant abilities were assessed. Results indicated that the phycocyanins were stable and possessed antioxidant properties. Interestingly, the Pseudanabaena phycocyanin was less likely to deteriorate under acidic conditions. CONCLUSIONS: Overall, we developed a promising and novel method for producing high functional phycocyanin concentrations at a low cost. The possibilities of adapting this new phycocyanin biorefinery to unique bioreactor utilization have also been discussed.

Characteristics and function of an extracellular polysaccharide from a green alga Parachlorella.

The green alga Parachlorella sp. BX1.5 is a new strain that can significantly coproduce lipids and polysaccharides, inside and outside the cells, respectively. This study aimed to investigate the characteristics and functional properties of the extracellular polysaccharide (EPS). Ethanol-extracted EPS from the cells grown in N-starved BG11 medium was found to be a novel acidic rhamnan of straight-chain type, with a high molecular mass of > 1.75 × 106 daltons. The water-soluble EPS exhibited high viscosity as sol, even at low concentrations, with 0.5 % EPS showing almost constant viscosity at 10-40 °C. Its addition to mayonnaise resulted in improved oil-off, suggesting its possible application as a thickener or food additive. Cells with added EPS were found to exhibit resistance to environmental stress conditions, such as heat, dryness, and decompression, and ultraviolet rays. Based on these rheological and biological effects, its unique properties with respect to biorefinery have been discussed here.

Coproduction of lipids and extracellular polysaccharides from the novel green alga Parachlorella sp. BX1.5 depending on cultivation conditions.

A novel strain of microalga Parachlorella sp. BX1.5 was isolated and its unique properties of producing lipids and extracellular polysaccharides (EPS) characterized. The cells could extracellularly produce a large amount of acidic EPS, when cultured in nitrogen-deficient BG110 medium (BG11-N) with 2 % CO2-air supply. The main component of intracellularly accumulated lipids was triacylglycerol (TAG), depending on the different cultivation conditions of BG11, BG11-N, BG11-P (phosphate depleted), and BG11-N-P (nitrogen and phosphate depleted). Fatty-methyl-esters (FAMEs), methyl-esterification of total lipids, consisted of abundant saturated C16 and unsaturated C18 fatty acids under the culture conditions. Cell spot assays on BG11 plates revealed the resistance of cells to pH 2-11, high temperatures of 50-70 °C, ultraviolet irradiation, and drought, under different culture conditions, thereby suggesting the biological significance of lipid and EPS accumulation. The prospects of BX1.5 as a dual producer has also been discussed for biorefineries.