金属离子对蜡状芽孢杆菌合成多聚γ-谷氨酸的影响

Effect of Adding Metal Ions on γ-Poly(glutamic acid) Production by Bacillus cereus

研究金属离子对蜡状芽孢杆菌合成多聚γ-谷氨酸(γ-PGA)的影响。通过在培养基中加入定量的Mn2+、K+、Fe3+、Mg2+、Ca2+、Mo6+、Zn2+、Co2+、Cd2+、Cu2+,定时取发酵液用原子吸收分光光度法测定蜡状芽孢杆菌合成γ-PGA过程中金属离子的消耗情况、菌体生物量及γ-PGA产量;在发酵培养基中,分别加入不同质量浓度的Mn2+、Ca2+、Zn2+、Co2+、Mo6+,通过组合不同金属离子以及控制各组合中离子质量浓度测定菌体生物量和γ-PGA含量的变化,结合金属离子的消耗量探讨金属离子对蜡状芽孢杆菌合成γ-PGA的影响。结果表明:在蜡状芽孢杆菌合成γ-PGA的过程中均消耗一定量的Mn2+、K+、Fe3+、Mg2+、Ca2+、Mo6+、Zn2+、Co2+,其中Mn2+、K+、Fe3+、Mg2+、Ca2+在生长代谢过程中利用较多,而Cd2+、Cu2+的质量浓度不变化;Mn2+是γ-PGA合成的必需元素,在其质量浓度为0.08g/L时,γ-PGA合成达最高峰(1.25g/L)。当Mn2+质量浓度为0.08g/L时,适当增加Ca2+质量浓度就能较大幅度提高γ-PGA合成量;同时固定Mn2+、Ca2+质量浓度,适量加入不同质量浓度的Zn2+、使γ-PGA的合成量增加明显,最高可达2.94g/L,而Mo6+对γ-PGA的合成影响不明显,但对菌体生物量的影响较大。

In this paper,the effects of some metal ions on the synthesis of poly-γ-glutamic acid（γ-PGA） by Bacillus cereus was investigated.Varied amounts of Mn2＋,K＋,Fe3＋,Mg2＋,Ca2＋,Mo6＋,Zn2＋,Co2＋,Cd2＋ and Cu2＋ were respectively added into the culture medium and their consumption,bacterial biomass,and the yield of γ-PGA were measured during fermentation at regular time intervals by atomic absorption spectrophotometry.The effects of Mn2＋ alone,Mn2＋（at 0.08 g/L） plus Ca2＋ at different concentrations,Mn2＋（at 0.08 g/L concentration） plus Ca2＋（at 1.0 g/L concentration） plus Zn2＋,Co2＋ or Mo6＋ at different concentrations on bacterial biomass and the yield of γ-PGA at the end of fermentation were investigated.The results showed that during the synthesis of γ-PGA,certain amounts of Mn2＋,K＋,Fe3＋,Mg2＋,Ca2＋,Mo6＋,Zn2＋ and Co2＋ were consumed,among which Mn2＋,K＋,Fe3＋,Mg2＋ and Ca2＋ displayed a higher amount,while the concentrations of Cd2＋ and Cu2＋ were kept unchanged.Mn2＋ was found to be neccessary for the synthesis of γ-PGA,and when its concentration was 0.08 g/L,γ-PGA synthesis reached its peak（1.25 g/L）.When the concentration of Mn2＋ was fixed at 0.08 g/L,increasing Ca2＋ concentration could greatly increase γ-PGA synthesis;when the concentrations of Mn2＋ and Ca2＋ were fixed,the addition of Zn2＋ promoted γ-PGA synthesis significantly,up to 2.94 g/L,and adding Mo6＋ had no obvious effect on the synthesis of γ-PGA,but a greater impact on bacterial biomass.