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Monitoring of simultaneous semi-solid state saccharification and fermentation of starch from raw materials to lactic acid

Starch containing raw materials represent preferable ingredients of more or less complex media to be used in sustainable biotechnological production of lactic acid. After upstream processing, prepared starch-based medium can adopt structure of suspension, gel, or semi-solid material with relatively low content of free liquid (water), as well as a combination thereof. Utilization of such heterogeneous media in bioprocess for lactic acid production requires additional efforts related to: adaptation of bioreactor construction and the medium mixing, definition of mass and energy transfer, selection of applicable analytical methods, their adaptation for bioprocess monitoring, etc. Several analytical methods were selected, adapted and tested for monitoring of Simultaneous Semi- Solid State Saccharification and Fermentation (S5F) of starch to lactic acid. Suspension of corn grits in demineralized water that consisted of two easy-separable phases (liquid and semi-solid phase) was used as a minimal medium for direct production of D-/L-lactic acid by Lactobacillus amylovorus DSM 20531T. Settling rate of corn grits particles, absorbance maxima and initial composition of heterogeneous medium were determined. During the S5F the reduction of semi- solid phase portion and concentration of polymeric substrates in the two phases were followed by using customized analytical methods.

bioprocess monitoring; simultaneous semi-solid state saccharification and fermentation; starch; raw material; direct lactic acid production; analytical methods

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