Online monitoring of the redox potential in microaerobic and anaerobic Scheffersomyces stipitis fermentations
2019
Bonan, Carolina I. D. G. | Biazi, Luiz E. | Santos, Samantha C. | Soares, Lauren B. | Dionísio, Suzane R. | Hoffmam, Zaira B. | Costa, Aline C. | Ienczak, Jaciane L.
OBJECTIVE: A correlation among different volumetric oxygen transfer coefficients (kLa) and the oxireduction potential (ORP) in batch fermentations using Scheffersomyces stipitis was evaluated. Experiments were performed using a mixture of xylose and glucose as the substrates. RESULTS: Microaerophilic condition (kLa = 4.9 h⁻¹) have shown to be suitable when compared to complete anaerobiosis (kLa = 0), providing an ethanol yield and a productivity after 48 h of 64.3% and 0.45 g ethanol L⁻¹ h⁻¹, respectively; the maximum ethanol titer obtained was 21.50 g ethanol L⁻¹. Values of ORP varying from − 270 to − 330 mV resulted in high ethanol production from xylose by S. stipitis. CONCLUSIONS: Different ORP values were found in anaerobiosis and kLa 4.9 h⁻¹, suggesting that for ethanol production by S. stipitis, values from − 270 to − 330 mV are favorable under the studied circumstances. In this ORP range, the greatest rates of xylose consumption and ethanol production were registered. ORP monitoring was demonstrated to be a suitable option for online control throughout the fermentation processes, which may provide a more efficient bioprocess operation with a very low O₂ concentration.
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