Application of redox potential control to improve ethanol productivity from inulin by consolidated bioprocessing

- K. marxianus achieves efficient ethanol production from inulin by ORP control.
- High cell viability at ORP-130 mV contribute to a better fermentative profile.
- MFA provides a better understand of the pathway for ethanol production by CBP.

Long fermentation time and high residual sugar concentration represent significant challenges for the ethanol production from inulin-containing feedstock by Kluyveromyces marxianus, which possesses the advantages of high temperature resistance, rapid growth and high level of native inulinase secretion. To solve the problems, an applicable strategy in ethanol production from inulin was developed. Batch fermentations were conducted by oxidation-reduction potential (ORP) control. When the ORP was controlled at −130 mV, the highest ethanol concentration and productivity, 97.7 g/L and 2.04 g/L/h, were achieved, with the residual sugar concentration of 3 g/L. The high cell viability ensured an effective conversion of total sugar to ethanol, leading to a low sugar concentration at the terminal. Metabolic flux analysis (MFA) demonstrated that significant differences in EMP, PPP and some nodes after pyruvate under different ORPs. With the increase of ORP from −150 to −100 mV, total sugar uptake rate increased from 195.11 to 223.13 C mmol/L/h. Controlling ORP at −130 mV was the most suitable strategy for the industrialization of ethanol production from inulin reported so far.

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