Screening and Identification of Astaxanthin Producing Strains and Study on Pigment Properties
Astaxanthin possesses numerous significant physiological and biological functions,making it highly promising for various applications.The demand for astaxanthin is steadily increasing both domestically and internationally.Consequently,the exploration of nature to identify astaxanthin-producing organisms with high yield,simple processes,easy cultivation,and large-scale production has always been a research objective.In this study,a pure culture method was employed to screen bacteria and fungi capable of producing astaxanthin in the growing environment of crayfish.Physiological and biochemical studies were conducted on the isolates exhibiting high astaxanthin yields.Additionally,molecular identification using 16S rRNA or ITS-rDNA was performed along with investigations into the stability and antioxidant activity of the produced astaxanthin.Fourteen strains capable of producing red pigment were screened from the crayfish's growing environment;among them,eleven strains were bacteria.Notably,strains P1,P2,and P3 demonstrated remarkable pigment-producing abilities.Morphological analysis combined with 16S rRNA molecular identification revealed that strain P1 belonged to Pseudomonas silesiensis while strain P2 was identified as Lysinibacillus sphaericus and strain P3 as Curtobacterium oceanosedimentum.Furthermore,three strains of pigment-producing fungi were also isolated from this environment;strains L1 and L2 exhibited substantial pigment production capacity.Morphological examination coupled with ITS-rDNA molecular identification confirmed that strain L1 corresponded to Kodamaea ohmeri while strain L2 was classified as Hasegawazyma lactosa.The stability of astaxanthin produced by strains P2 and L1 was assessed.The findings revealed that temperature,light,and oxygen exerted significant influence on the stability of astaxanthin.Light exposure and oxygen were identified as the primary factors contributing to the degradation of astaxanthin,while short-term heat did not significantly affect its stability.Furthermore,the antioxidant activity of astaxanthin was evaluated,demonstrating that both strains exhibited potent scavenging effects against hydroxyl radicals and 1,1-diphenyl-2-picrylhydrazyl(DPPH)radical.Notably,strain L1 displayed a stronger scavenging ability compared to Vitamin C.
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