pH对灵芝液态发酵代谢物及抗氧化活性的影响

已有研究报道灵芝栽培生长的最适pH在中性偏酸环境，在碱性范围的生长及代谢情况鲜见报道。本研究主要探究广泛pH对灵芝液态发酵代谢物及其抗氧化活性的影响。采用摇瓶液态培养后分析代谢物中灵芝三萜、胞内外多糖、菌丝体蛋白及抗氧化活性等指标，系统比较灵芝菌丝体在pH值2-11的生长和代谢情况。研究结果表明，灵芝菌丝体生长、合成灵芝三萜、胞内多糖、30E胞外多糖、菌丝体蛋白和菌丝体水解氨基酸的最适pH值分别为10、3、2、7、2和2。对应结果分别为17.13 g/L、33.86 mg/g、72.73 mg/g、7.86 g/L、71.42 mg/g和107.10 mg/g。比对照分别提高28.5%、77.3%、22.4%、96.5%、97.1%和70.8%。胞内多糖组分1和组分2最高分子量均在初始pH 4，分别为1.016×10⁸ g/mol和9.280×10⁴ g/mol，胞外多糖组分1最高分子量在初始pH 10，为4.946×10⁶ g/mol；对菌丝体的总抗氧化能力、1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2- picrylhydrazyl，DPPH)自由基清除能力、羟自由基清除能力分析结果表明最佳的初始pH分别为3、7、9。本研究为液态发酵方式下灵芝生长及其代谢物定向调控发酵的工艺优化提供参考依据，同时发现灵芝菌丝体中优质蛋白及抗氧化活性可在功能性食品和化妆品领域推广应用。

Effects of pH on metabolites and antioxidant activities of Ganoderma lingzhi liquid fermentation

The optimum pH for Ganoderma lingzhi cultivation and growth is neutral and acidic, while the growth and metabolism of G. lingzhi in alkaline range are rarely reported. In this study, the effects of pH on metabolites and antioxidant activities of G. lingzhi liquid fermentation were investigated. Triterpenoids, intracellular and extracellular polysaccharides, mycelial proteins and antioxidant activities of G. lingzhi metabolites generated in liquid culture in shaking flask were analyzed. The growth and metabolism of G. lingzhi mycelia in the pH range from 2 to 11 were systematically compared. The results showed that the optimum pH values for the growth of G. lingzhi mycelium and the syntheses of triterpenes, intracellular polysaccharides, extracellular polysaccharides, mycelial protein and hydrolyzed amino acid were 10, 3, 2, 7, 2 and 2, respectively. Under such pH conditions, the corresponding yields of mycelia, triterpenes, intracellular polysaccharides, extracellular polysaccharides, mycelial protein and hydrolyzed amino acid were 17.13 g/L, 33.86 mg/g, 72.73 mg/g, 7.86 g/L, 71.42 mg/g and 107.10 mg/g, respectively. 28.5%, 77.3%, 22.4%, 96.5%, 97.1% and 70.8% higher respectively as compared with those of the experimental control. The maximum molecular weights of components 1 and 2 of intracellular polysaccharides were 1.016×10⁸ g/mol and 9.280×10⁴ g/mol respectively at initial pH 4, while the maximum molecular weight of component 1 of extracellular polysaccharides was 4.946×10⁶ g/mol at initial pH 10. Total antioxidant capacity of mycelium, scavenging capacity of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and hydroxyl radical scavenging capacity showed the highest under optimal initial pH of 3, 7 and 9 respectively. This study provided a reference for the optimization of fermentation process of G. lingzhi growth and metabolite directional regulation under liquid fermentation mode, and found that the high quality protein and antioxidant activity in G. lingzhi mycelia can be popularized and applied in functional food and cosmetics.