Optimization Of The Fermentation Process Of Spirulina Platensis By Lactic Acid Bacteria And Determination Of The Anti-aging Effect Of The Fermentation Products

The development of functional foods from the perspective of dietary nutrition regulation is one of the important strategies to improve the body's aging and even prevent and treat related chronic diseases.Spirulina is rich in proteins,vitamins,minerals,and other nutrients necessary for human growth.It exerts anti-aging,anti-oxidation,hypoglycemic and other effects.It is a nutritionally comprehensive dietary supplement and ingredient of many medicines and food preparations.Lactic acid bacteria are a kind of microorganisms that are beneficial to the host.The bacteria themselves and their fermentation products have antibacterial,antioxidant,and other probiotic effects,and can also produce pleasant flavor substances.At present,there is no research report on the anti-aging aspect of the product of Spirulina platensis fermented by lactic acid bacteria.The main object of this study is the anti-aging activity of the products of Spirulina platensis fermented by lactic acid bacteria by explored.The main aims of the study were the preparation of the fermentation product and the evaluation of the activity.Firstly,the tolerance ability of lactic acid bacteria used in this study was measured,and the combination of fermentation bacteria was screened.The addctive amount and proportion of Spirulina powder,glucose and peptone in the fermented medium were determined by single-factor analysis,and the best combination of various single-factors was determined by the orthogonal experiment,thus the fermentation products of Spirulina platensis were obtained.Secondly,Caenorhabditis elegans(C.elegans)was used as an evaluation model to study the effect of Spirulina fermentation products.The heat stress,oxidative stress,and lifespan of C.elegans were studied.Based on the results of RNA-seq,the anti-aging effect and the potential molecular mechanisms of the fermented products of Spirulina platensis was explored,providing the theoretical basis and technical details for the development of microbe-based functional food and new perspectives to improve the quality of life.The results showed that strains of Lactobacillus plantarum DY-1,Bacillus coagulans GIM1.645,Lactobacillus acidophilus KDB-03,and Lactobacillus casei KDB-LC used in this study were all showed good tolerance of salt,bile salt,artificial gastric and intestinal juice and grew well in Spirulina fermentation medium.The optimization of the fermentation process showed that the optimum parameter were:Spirulina platensis powder 3.0%,glucose 4.0%,peptone 1.5%,inoculation dose 4×10~5 CFU/mL with the proportion of Lactobacillus Plantarum DY-1,Bacillus coagulans GIM1.645,Lactobacillus acidophilus KDB-03,and Lactobacillus casei KDB-LC 1:1:1:1.Under the above condition,the fermented products of Spirulina platensis by lactic acid bacteria showed an optimum DPPH radical scavenging ability.The resistance of stress and the anti-aging effect of the fermented products of Spirulina were meaured by C.elegans model.The results showed that the fermented products could improve the capacity against heat stress,and the survival rate was the highest at the concentration of 5.0 mg/mL,which was 24.6% higher than the blank control group.The tolerance against oxidative stress was also improved,and the survival rate was the highest at the concentration 3.0 mg/mL,which was 9.3% higher than that of the blank control group,and 6.2% higher than that of the unfermented Spirulina medium.The average lifespan of C.elegans,was prolonged at the concentration of 5.0 mg/mL,which was 3.2 days longer than that of the blank control group,and 1.6 days longer than that of the unfermented Spirulina medium.According to the results of the RNA-seq,the longevity improvement and stress resistance of the fermented products involved in the upregulation of the daf-16,daf-18,pptr-1,smk-1,hsf-1,and skn-1 expression,suggesting that the Spirulina fermentation product might play their anti-aging role via the insulin/IGF-1 signaling pathway.In conclusion,the fermentation products of Spirulina platensis by lactic acid bacteria showed a developmental potential.Innovation points of this research:1.The effect of lactic acid bacteria-based fermentation on Spirulina was investigated,providing the theoretical basis and technical support for new high value-added microbial foods.2.The anti-aging effect of the fermented products of Spirulina were evaluated by C.elegans model,and the potential molecular regulation mechanisms was preliminarily revealed,providing a theoretical basis for the future development of related products.