A Physiological Characterization in Controlled Bioreactors Reveals a Novel Survival Strategy for Debaryomyces hansenii at High Salinity and Confirms its Halophilic Behavior

Abstract

Debaryomyces hansenii is traditionally described as a halotolerant non-conventional yeast, being the model organism for the study of osmo- and salt tolerance mechanisms in eukaryotic systems for the past 30 years. However, unravelling of D. hanseniis biotechnological potential has always been difficult due to the persistent limitations in the availability of efficient molecular tools described for this yeast. Additionally, there is a lack of consensus and contradictory information along the recent years that limits a comprehensive understanding of its central carbon metabolism, mainly due to a lack of physiological studies in controlled and monitored environments. Moreover, there is controversy about the diversity in the culture conditions (media composition, temperature and pH among others) used by different groups, which makes it complicated when trying to get significant conclusions and behavioural patterns. In this work, we present for the first time a physiological characterization of D. hansenii in batch cultivations using highly instrumented and controlled lab-scale bioreactors. Our findings contribute to a more complete picture of the central carbon metabolism and the external pH influence on the yeast ability to tolerate high Na+ and K+ concentrations. Finally, the controversial halophilic/halotolerant character of this yeast is further clarified.