Efficient production of poly γ‐ d ‐glutamic acid from the bloom‐forming green macroalgae, Ulva sp., by Bacillus sp. SJ‐10

Numerous studies on poly γ‐ d ‐glutamicacid (γ‐PGA) production have investigated terrestrial renewable sources for reducing production costs, but there are no studies using waste marine resources so far. We aimed to develop a cost‐effective production method of γ‐ d ‐PGA by Bacillus sp. SJ‐10 using green macroalgae ( Ulva sp.) as a major substrate without hydrolysis pretreatment. The SJ‐10 was shown to not only cause immediate tissue degradation of the Ulva membrane but also grew well as a sole substrate. The γ‐ d ‐PGA yield was 6.29 ± 0.34 g/L under optimized conditions via the response surface method, and the produced γ‐ d ‐PGA had a thermal decomposition temperature of 310°C and molecular weight of 250–1780 kDa. The calculated cost efficiency for the final yield was 32% when compared with complex media. Therefore, the present study provided a strategy for promoting an ecofriendly and cost‐effective means to produce γ‐ d ‐PGA via a marine renewable resource.