Redox potential as a key parameter for monitoring and optimization of xylose fermentation with yeast Spathaspora passalidarum under limited-oxygen conditions.

The determination of optimum values of volumetric oxygen transfer coefficient (ka) for Spathaspora passalidarum is an important aspect for the optimization of ethanol production from pentoses since oxygen plays a key role on yeast metabolism. By studying the fermentation of a xylose and glucose mixture, the highest ethanol volumetric productivity was achieved at a ka of 45 h (1.12 g L h), reducing the fermentation time to half when compared to other oxygen-limiting conditions that were considered optimum for other native strains, besides increasing xylose consumption rates.

Online monitoring of the redox potential in microaerobic and anaerobic Scheffersomyces stipitis fermentations.

Objective: A correlation among different volumetric oxygen transfer coefficients (ka) 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 (ka = 4.