Simultaneous Saccharification And Fermentation Of Cassava To Succininc Acid By Escherichia Coli NZN111

Succinic acid is one of the most important platform chemicals.The prospective environmental motivated the development of bio-based succinate industry.However,bio-based succinate is still facing the challenge of competitive cost against petrochemical-based alternatives.In this study,the production of succinic acid from cassava starch and raw cassava instead of glucose by Escherichia coli NZN111 was investigated.During the two-stage fermentation,simultaneous saccharification and fermentation(SSF)was applied in the anaerobic stage.In order to compromise the temperature for saccharification and succinic acid production,succinic acid fermentation was conducted at higher temperatures than 37 ℃.The results showed that both the productivity(2.10 g/L/h)and specific productivity(171 mg/(g DCW h))in the process conducted at 40 ℃ were higher than those in the cultivation conducted at 37 ℃(1.69 g/L/h and 132 mg/(g DCW h)).The yield of succinic acid based on the amount of added starch reached the highest level(0.86 g/g)when 116.8 g/L cassava starch was supplemented to the fermenter and the liquefied cassava starch was almost totally hydrolyzed in the SSF process.With the improved cell density,127.13 g/L of succinic acid was obtained and the productivity in the whole anaerobic stage was 3.23 g/L/h.When the liquefied crude cassava powder was directly used in the SSF process,106.17 g/L of succinic acid was formed and the yield of added cassava powder to succinic acid was 0.66 g/g which was close to the theoretical yield.The result showed that crude cassava powder could be another cheaper raw material for succinic acid formation.