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Acta Prataculturae Sinica ›› 2026, Vol. 35 ›› Issue (7): 201-216.DOI: 10.11686/cyxb2025291

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Optimization of fermentation and ultrasound-assisted extraction parameters for alfalfa saponins

Wu LI1(), Jia-jing LI1(), Jie-bing LI1, Zhen-zhou LI4, Ming GUO1,2,3, Yan NIU5, Hao SUN1,2,3, De-feng LI1,2,3, Ying-hua SHI1,2,3, Zhen-tian LI1,2,3, Bo-shuai LIU1,2,3, Ya-lei CUI1,2,3, Zhi-chang WANG1,2,3, Yong-tao LI4, Xiao-yan ZHU1,2,3()   

  1. 1.College of Animal Science and Technology,Henan Agricultural University,Zhengzhou 450046,China
    2.Henan Key Laboratory of Innovation and Utilization of Grassland Resources,Zhengzhou 450046,China
    3.Henan Forage Engineering Technology Research Center,Zhengzhou 450046,China
    4.College of Veterinary Medicine,Henan Agricultural University,Zhengzhou 450046,China
    5.Henan Provincial Animal Husbandry Bureau Forage and Feed Station,Zhengzhou 450002,China
  • Received:2025-07-14 Revised:2025-10-09 Online:2026-07-20 Published:2026-05-21
  • Contact: Xiao-yan ZHU

Abstract:

This study aimed to optimize the fermentation and ultrasound-assisted extraction processes for alfalfa (Medicago sativa) saponins. Saccharomyces cerevisiaeBacillus subtilis, and Lactobacillus casei were selected as fermentation strains for testing. Single-factor experiments were conducted to compare three single strains and their 1∶1∶1 mixed culture fermentation, and to systematically evaluate the influence of fermentation time (24, 48, 72, and 96 hours), glucose addition (0.05, 0.10, 0.15, and 0.20 g per g of alfalfa powder), fermentation solid-to-liquid ratio [1∶0.8, 1∶1.2, 1∶1.6, and 1∶2.0 (g∶mL)], and strain inoculum volume (0.04, 0.06, 0.08, and 0.10 mL) on the saponin yield. The interactions between strain type and fermentation parameters were also assessed, with three independent replicates for each treatment. Based on the results, the optimal strain type combination and key fermentation parameters were determined, and a Box-Behnken design (BBD) was applied to further optimize the fermentation conditions. Model fit and reproducibility were evaluated through three independent validation experiments. Furthermore, using the optimal fermented product as the raw material, the effects of ultrasonication time (45, 60, 75, and 90 min), ultrasonication solid-to-liquid ratio (1∶10, 1∶20, 1∶30, and 1∶40), and ultrasonication temperature (25, 37, 49, and 61 ℃) on saponin yield were investigated. The interactions between ultrasonication parameters and strain type were analyzed, and BBD was employed to optimize the extraction process. The results showed that the 1∶1∶1 mixed-culture fermentation achieved a significantly higher saponin yield than single-strain fermentation (P<0.05). The optimal fermentation conditions were a solid-to-liquid ratio of 1∶1.27, a fermentation time of 50.3 hours, and a strain inoculation volume of 0.062 mL. Under this regime the saponin yield was 11.68%. Under the combined fermentation and ultrasound-assisted extraction conditions (solid-to-liquid ratio 1∶23.1, ultrasonication time 72.7 min, and temperature 47.3 ℃), the saponin yield increased to 13.87%, which was 98.4% higher than that of the control (P<0.05). This study developed an efficient and eco-friendly fermentation-ultrasound synergistic extraction process, providing technical support for the efficient extraction and subsequent high-value utilization of alfalfa saponins.

Key words: alfalfa saponins, probiotic fermentation, ultrasonic extraction, process optimization, bioactive components