Debaryomyces hansenii Is a Real Tool to Improve a Diversity of Characteristics in Sausages and Dry-Meat Products.

Debaryomyces hansenii yeast represents a promising target for basic and applied biotechnological research It is known that D. hansenii is abundant in sausages and dry-meat products, but information regarding its contribution to their characteristics is blurry and contradictory. The main goal in this review was to define the biological contribution of D. hansenii to the final features of these products. Depending on multiple factors, D. hansenii may affect diverse physicochemical characteristics of meat products. However, there is general agreement about the significant generation of volatile and aromatic compounds caused by the metabolic activities of this yeast, which consequently provide a tendency for improved consumer acceptance. We also summarize current evidence highlighting that it is not possible to predict what the results would be after the inoculation of a meat product with a selected D. hansenii strain without a pivotal previous study. The use of D. hansenii as a biocontrol agent and to manufacture new meat products by decreasing preservatives are examples of exploring research lines that will complement current knowledge and contribute to prepare new and more ecological products.

A physiological characterization in controlled bioreactors reveals a novel survival strategy for Debaryomyces hansenii at high salinity.

Debaryomyces hansenii is traditionally described as a halotolerant non-conventional yeast and has served as a model organism for the study of osmotolerance and salt tolerance mechanisms in eukaryotic systems for the past 30 years. However, unraveling of D. hansenii's 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 little consistency in the culture conditions (media composition, temperature, and pH among others) used by different groups, which makes it complicated when trying to get prevalent conclusions on behavioral patterns. In this work, we present for the first time a characterization of D. hansenii in batch cultivations using highly 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's ability to tolerate high Na+ and K+ concentrations, pointing to a differential effect of both salts, as well as a positive effect in cell performance when low environmental pH values are combined with a high sodium concentration in the media. Finally, a novel survival strategy at very high salinity (2 M) is proposed for this yeast, as well as potential outcomes for its use in industrial biotechnology applications. TAKE AWAY: High salt concentrations stimulate respiration in Debaryomyces hansenii. Sodium exerts a stronger positive impact on cell performance than potassium. µmax is higher at a combination of low pH, high salt, and high temperature. Concentrations of 2 M salt result in slower growth but increased biomass yield. The positive effect of salts is enhanced at low glucose concentration.

Overlapping responses between salt and oxidative stress in Debaryomyces hansenii.

Debaryomyces hansenii is a halotolerant yeast of importance in basic and applied research. Previous reports hinted about possible links between saline and oxidative stress responses in this yeast. The aim of this work was to study that hypothesis at different molecular levels, investigating after oxidative and saline stress: (i) transcription of seven genes related to oxidative and/or saline responses, (ii) activity of two main anti-oxidative enzymes, (iii) existence of common metabolic intermediates, and (iv) generation of damages to biomolecules as lipids and proteins. Our results showed how expression of genes related to oxidative stress was induced by exposure to NaCl and KCl, and, vice versa, transcription of some genes related to osmotic/salt stress responses was regulated by H2O2. Moreover, and contrary to S. cerevisiae, in D. hansenii HOG1 and MSN2 genes were modulated by stress at their transcriptional level. At the enzymatic level, saline stress also induced antioxidative enzymatic defenses as catalase and glutathione reductase. Furthermore, we demonstrated that both stresses are connected by the generation of intracellular ROS, and that hydrogen peroxide can affect the accumulation of in-cell sodium. On the other hand, no significant alterations in lipid oxidation or total glutathione content were observed upon exposure to both stresses tested. The results described in this work could help to understand the responses to both stressors, and to improve the biotechnological potential of D. hansenni.

Inoculation with a terroir selected Debaryomyces hansenii strain changes physico-chemical characteristics of Iberian cured pork loin.

Debaryomyces hansenii Lr1, previously isolated from naturally fermented cured pork loin ("lomo embuchado"), was used to inoculate Iberian pork loin under four different conditions. In all cases, specifically inoculated D. hansenii yeasts grew on the surface of the product and affected its physico-chemical and sensory characteristics. Inoculated pork loin kept higher water activity and pH and possessed lower sodium content than control samples at the end of the 90 days ripening period. Moreover, inoculation with Lr1 yeast did not change the general profile of fatty acids but modified the levels of volatile and aroma compounds by decreasing aldehydes and increasing esters and alcohol compounds. Principal Component Analysis (PCA) of the different physico-chemical parameters that were determined showed a clear separation between the samples indicating that they were different. A tendency in consumers acceptance to prefer cured pork loin specifically inoculated with the higher amounts of yeasts used in this study was observed.

Debaryomyces hansenii Strains from Valle De Los Pedroches Iberian Dry Meat Products: Isolation, Identification, Characterization, and Selection for Starter Cultures.

Yeasts, filamentous fungi, and bacteria colonize the surface of fermented sausages during the ripening process. The source of this microbiota is their surrounding environment, and is influenced by the maturing conditions and starter cultures. Debaryomyces hansenii was previously isolated from several dry-cured meat products and associated with the lipolytic and proteolytic changes that occur in these products, influencing their taste and flavor. Therefore, this study isolated the yeast microbiota present in the casing from different meat products ("lomo," "chorizo," and "salchichón") from the Valle de los Pedroches region in southern Spain. D. hansenii was by far the most abundant species in each product, as all 22 selected isolates were identified as D. hansenii by biochemical and/or molecular methods. In contrast, no yeasts were found in the meat batter. These data constitute the first study of the yeasts present in "lomo" sausages and particularly the highly appreciated Valle de los Pedroches "lomo" sausages. Furthermore, the resistance of these isolates to different pHs, temperatures, and saline stress was studied, together with their catabolic characteristics. Based on the results, certain isolates are proposed as valuable candidate starter cultures that could improve both the manufacture and the flavor of such dry-cured meat products, and provide an understanding of new mechanisms involved in stress tolerance. Applied mediumscale industrial tests are currently in progress.