Abstract: The effects of carbon source and manganese ion on the production of γ -poly (glutamate) ( γ -PGA) was investigated.The results showed that the production of γ -PGA was different on varions carbon sources, and among those, citric acid and glycerol were much better than others.The production of γ -PGA was increased to 15.72g·L ^-1 by using the citric acid and glycerol as a combined carbon source.It was also found that the production of γ -PGA could be regulated by control of manganese ion concentration in the medium.Without Mn ²⁺ ,there was no γ -PGA produced.The production of γ -PGA was increased by increasing Mn ²⁺ concentration, the optimal concentration of Mn ²⁺ was 39.0mg·L ^-1 .The composition and morphology of γ -PGA were also affected by Mn ²⁺ .