The Effect Of Different Calcium Concentration On Physiology And Biochemistry Characteristics Of Nostoc Sphaeroides

Nostoc sphaeroides is an edible cyanobacterium, which lived in rice fields of HefengCounty (China). Owing to the extensive use of chemical fertilizers, pesticides andherbicides, the annual yield of N.sphaeroides has been reduced to0.5ton from themaximum annual yield of25tons. It’s the recognition for nutritional value andmedicinal value of N.sphaeroides that gives rise to the market demand. Quite a lot ofresearchers devoted themselves to the artificial breeding and theoretical research ofN.sphaeroides and major breakthrough is made. However, there is still an obstacle inlarge-scale cultivation that the spherical colony will are prone to rupture when theN.sphaeroides were breeded in artificial culture. In this paper, we investigate the effect ofcalcium ion on the growth and metabolism, the biochemical characteristics and thephotosynthesis of N.sphaeroides and try to find the control method of its rupture. Thiswork provides important technical support for artificial breeding condition ofN.sphaeroides.The CaCl2concentration in the BG-110Medium was optimized by varying it from0to2450(0,123,245,980,2450) μmol/L. It was found that N.sphaeroides has the highestgrowth rate (92±4mg DW·L-1·d-1), the minimum number of rupture of groups,relatively high firmness (27.9±2.0g) and the highest springiness (45.1±4.8%) whenthe CaCl2concentration is980μmol/L. While lower calcium concentration (245μmol/LCaCl2) would lead to the fracture phenomenon in groups of N.sphaeroides, resulting inthe final failure of aquaculture, what’s more it would also cause the springiness(37.9±3.1%) and firmness (25.3±1.9g) decline of N.sphaeroides,. It is concluded that averagediameter and rupture number of N.sphaeroides decreases with the increasing of calciumconcentration by the statistics analysis of the proportion of different diameterN.sphaeroides at different calcium concentrations.At the end of the experiment, the content of protein, polysaccharide and fatty acidcomposition were measured. The results showed that as the calcium ion concentrationincreasing, the protein content decreased while the content of polysaccharide increased.The composition and content of total fatty acid (remained at about1.8%of dry weight)was not affected by calcium ion concentration. The reaction activity of Superoxidedismutase (SOD) and Polyphenol oxidase (PPO) declined with the rise of calcium ionconcentration. Phenylalanine ammonia-lyase (PAL) exhibited higher activity at lowercalcium concentration, but lower activity at higher calcium concentration.The study found that the chlorophyll a content of N.sphaeroides declined with theincrease of calcium ion concentration at the end of the cultivation. We found that whenCaCl2concentrations is high (980,2450μmol/L) in the growth environment, theN.sphaeroides has both higher apparent (α) and net photosynthetic efficiency(Pm), whenCaCl2concentrations is low (0,123μmol/L) in the growth environment, the N.sphaeroideshas both lower apparent (α) and net photosynthetic efficiency(Pm).And the maximum electron transport (rETRm) declined with the decreaaing CaCl2concentrations. Resultsindicated that at higher calcium concentration, per unit chlorophyll a of N.sphaeroides hashigher photosynthetic efficiency and photosynthetic capacity.