微生物固态发酵商桔梗的工艺优化及抗氧化活性分析

Microbial Solid-state Fermentation Process Optimization and Antioxidant Activity Evaluation of Platycodonis Radix from Shangcheng

摘要:

【目的】探究微生物发酵对商桔梗中活性物质的影响。【方法】以总黄酮和总多酚质量分数为指标筛选出优势菌种，将优势菌种添加到商桔梗中，以发酵时间、发酵温度、料液比、接种质量分数为影响因素进行单因素试验和正交试验，以获得最佳发酵工艺条件。以DPPH自由基清除率、ABTS⁺自由基清除率和总还原力为指标，分析微生物发酵对商桔梗体外抗氧化活性的影响。 【结果】优势发酵菌为黑曲霉H，最优发酵工艺条件为：发酵时间4 d、发酵温度33 ℃、料液比1 g∶5.5 mL、接种质量分数11%。在此条件下总黄酮质量分数为（5.32±0.13） mg/g，比未发酵时提高了1.19倍；总多酚质量分数为（156.88±0.88） mg/g，比未发酵时提高了1.20倍。未发酵商桔梗与发酵商桔梗DPPH自由基清除率的IC₅₀值分别是0.030、0.025 mg/mL，ABTS⁺自由基清除率的IC₅₀值分别是0.033、0.021 mg/mL，发酵商桔梗的总还原力也有所增强。【结论】利用黑曲霉H对商桔梗进行发酵，可有效提升其活性物质质量分数和抗氧化能力，为商桔梗的进一步研究与开发提供了理论依据。

Abstract:

[Objective] This study aims to explore the effect of microbial fermentation on the active substances in Platycodonis Radix from Shangcheng. [Method] With the mass fractions of total flavonoids and total polyphenols as evaluation indicators, the dominant microbial strains were screened. The selected strain was subsequently applied to the fermentation of Platycodonis Radix from Shangcheng. Single-factor experiments and orthogonal experiments were conducted to optimize the critical fermentation parameters including time, temperature, solid-to-liquid ratio, and inoculum mass fraction. The effect of microbial fermentation on the antioxidant activity in vitro of Platycodonis Radix from Shangcheng was evaluated with DPPH free radical scavenging rate, ABTS⁺ free radical scavenging rate, and total reducing power as indicators. [Result] Aspergillus niger (A. niger) H was identified as the dominant strain for fermentation. The fermentation conditions were optimized as follows: fermentation with a solid-to-liquid ratio of 1 g∶5.5 mL and an inoculum mass fraction of 11% at 33 ℃ for 4 d. Under these conditions, the mass fraction of total flavonoids reached (5.32±0.13) mg/g (representing a 1.19-fold increase compared with that before fermentation) and that of total polyphenols achieved (156.88±0.88) mg/g (representing a 1.20-fold enhancement compared with that before fermentation). Platycodonis Radix from Shangcheng before and after fermentation showed the IC₅₀ values of 0.030 mg/mL and 0.025 mg/mL for scavenging DPPH free radicals and 0.033 mg/mL and 0.021 mg/mL for scavenging ABTS⁺ free radicals, respectively. Total reducing power of Platycodonis Radix from Shangcheng was also substantially enhanced after fermentation. [Conclusion] The fermentation of Platycodonis Radix from Shangcheng with A. niger H could effectively improve the mass fractions of active ingredients and antioxidant capacity, which provided a theoretical basis for further research and development of Platycodonis Radix from Shangcheng.