| Nostoc sphaeroides kützing was a kind of fresh water cyanobacteria which can be used in edible and ancient books indicate that it could be used as medicine,which was rich in nutrition and balanced,known as "green bird’s nest ",Nostoc sphaeroides was a new food raw materials.At present,the wild resources had been endangered because of habitat deterioration,mainly in artificial culture,but because of the lack of germplasm resources and breeding varieties were extremely single,only dark green Nostoc sphaeroides.The aim of this study was to select a new algal plant with good growth performance,high nutritional value and suitable for large-scale cultivation.This could enrich the germplasm resources of Nostoc sphaeroides,which is beneficial to the breeding of new varieties of Nostoc sphaeroides,the realization of large-scale cultivation,and to the industrial development of Nostoc sphaeroides.To that end,this article studied on 16 S r DNA sequencing,analysis of nutrient components,morphological characteristics of life history and large-scale cultivation of the emerald green Nostoc sphaeroides,the results were as follows:(1)After morphological and 16 S r DNA sequence homologous comparisons: The emerald green Nostoc sphaeroides was a new algae strain of Nostoc sphaeroides.The results of nutritional composition and pigment content analysis showed that: The Phycoerythrin content of dark green Nostoc sphaeroide(0.244 mg/g FW)was about 7.625 times of emerald green Nostoc sphaeroide(0.032 mg/g FW),the contents of their nutrient species,protein and crude polysaccharide were similar,the above results show that the color change didn’t change the main nutritional value of Nostoc sphaeroide,the color was mainly caused by the difference of Phycoerythrin content.(2)The results of the study on the morphological characteristics of life history confirm that: The life history of the hormogonia is composed of four stages: the minimal colonies,filamentation of seriate colonies,the different diameter colonies.In the process of development,the propagation methods include hormogonia and budding reproduction,proliferationby "algae body division".As the colonies size increases,budding rate and breakage rate had obvious scale effect.In addition,the heterocyst differentiation is promoted by the number of algal cells,and was related to the formation of "embryonic bud" of budding reproduction and the fracture of single algae filaments between groups in the later stage of budding,the results show that hormogonia was the key targets of growth and differentiation regulation.(3)The results of large-scale cultivation showed that: The light duration of 24 h/d,low inoculum,and suitable for high light intensity could promote algal growth,With 400 L glass tank,1 T runway pool and 15 runway pool,the emerald green Nostoc sphaeroides could be cultured on a large scale,and their wet weight growth rate and unit yield were 400 L glass tank >1 T runway pool and 15 runway pool,static culture could also effectively promote the growth of the emerald green Nostoc sphaeroides too.In addition,the growth rate of wet weight was inversely proportional to the yield of dry matter.All the above results showed that 400 L glass tanks had the best effect of large-scale cultivation,the growth rate of wet weight would be a key index of control in the process of large-scale cultivation.Above all,The emerald green Nostoc sphaeroides was a new algae strain of Nostoc sphaeroides,and the color change was mainly caused by the different Phycoerythrin content,It had the main nutritional value of Nostoc sphaeroides,the vegetative proliferation of the emerald green Nostoc sphaeroides was mainly caused by hormogonium and germinal reproduction,it was suitable for large-scale cultivation with various culture modes,the large-scale cultivation of Nostoc sphaeroides was feasible and worthy of further study. |
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