| Photosynthetic bacteria can carry out photosynthesis in a completely anaerobic state with the help of light energy in nature.In the process of photosynthesis,a variety of pigments and nutrients such as carotenoids and chlorophyll are produced.These biomasses can be used in nutritional supplements,medicines and animal feed with great economic benefits.Among them,carotenoids in photosynthetic bacteria contain about 60% β-carotene,which can be used as a source of vitamin A in the human body and has functions such as scavenging free radicals,anti-inflammatory,immune regulation,and anti-tumor.Since the production of carotene by microbial fermentation is superior to chemical synthesis in terms of quality,technology,resources and cost,the production of β-carotene by photosynthetic bacteria has attracted more and more attention.In this experiment,Rhodospirllum rubrum was isolated and purified by organic solvent extraction,thin layer chromatography and silica gel column chromatography,and finally identified by high performance liquid chromatography and liquid chromatography.The product is rich in β-carotene.Single factor experiments were used to explore the effects of temperature,ultrasonic extraction time,light intensity,and yeast extract concentration on the β-carotene production of Rhodospirllum rubrum production of β-carotene.The stability,antioxidant activity and cytotoxicity of β-carotene in light,temperature,p H and metal ions were calculated,and the antioxidant capacity was determined and the viability of murine fibroblasts was studied.The results showed that the product obtained by the final identification containedβ-carotene.The optimized analysis of β-carotene by single factor showed that the optimal conditions for β-carotene production were the temperature of 30 ℃,the ultrasonic extraction time of 30 min,the light intensity of 3000 Lux,and the yeast extract concentration of 1.5 g/L.And the obtained β-carotene yields were 10.02 mg/L,10.10 mg/L,9.47 mg/L,and 9.83 mg/L,respectively.The optimum yield of β-carotene was 10.24 mg/L under the optimum conditions determined by response surface methodology.In the stability experiment,it was found that light had the greatest effect on the stability of β-carotene,and metal ions had the least effect on the stability of β-carotene.The antioxidant activity and cytotoxicity of β-carotene derived from photosynthetic bacteria were also discussed.The results show that the DPPH scavenging rate of β-carotene can reach up to about 63.05%,and it has certain hydroxyl radical scavenging and total reducing ability.The cytotoxicity ofβ-carotene extracted from photosynthetic bacteria,Rhodospirillum rubrum,was detected by MTT method.The results confirmed that the β-carotene was not toxic to cells when the content of β-carotene did not exceed 1.25 mg/L.In conclusion,the conditions were optimized using the β-carotene produced by the photosynthetic bacteria Rhodospirllum rubrum,and its stability and physiological activity were studied.The results confirmed that Rhodospirillum rubrum produces β-carotene,which has the potential to replace chemical synthesis and other microbial synthesis.Therefore,it is expected to make some contributions to further explore the application scope of photosynthetic bacteria β-carotene and improve the production of photosynthetic bacteria biopigment with Rhodospirillum rubrum as the research core. |
