A Physiological Characterization in Controlled Bioreactors Reveals a Novel Survival Strategy forDebaryomyces hanseniiat High Salinity and Confirms its Halophilic Behavior

Abstract

4Debaryomyces hansenii is traditionally described as a halotolerant non-conventional yeast, being 1 5

Cell Factories for Industrial Production Processes: Current Issues and Emerging Solutions

“…Additionally, Gustafsson and Norkrans in 1976 [93] and Adler et al in 1985 [94], described the role of glycerol production and accumulation as a compatible solute in response to high extracellular osmolarity. More recent work on the characterization of D. hansenii in controlled bioreactors, revealed that high salt concentrations are necessary for optimal cell performance in this yeast, especially sodium salts [41]. This confirmed that D. hansenii is halophilic rather than simply halotolerant as previously hypothesized.…”

“…Saline water may not be suitable for the prior biomass pretreatment and enzymatic hydrolysis steps, which are sensitive to salinity deviations [40]. Despite this, its use in the fermentation step would reduce the overall freshwater demand of the process and hence production costs [41].…”

“…This resulted in a shift in carbon flux toward lipid synthesis and lipid accumulation increased threefold [59]. The use of crude glycerol also effects lipid production and accumulation, especially when stearin is used as co-substrate [41]. As a result of recent advancements in synthetic biology and metabolic engineering tools, heterologous expression of genes is now relatively straightforward.…”

“…Very high concentrations of around 2 M, however, trigger a shift in metabolic strategy, where µ max is decreased and the biomass yield on substrate is increased. Hence, the survival strategy is switched from growing at the fastest possible rate to maximizing overall yield: slowing down the growth rate whilst still proliferating [41]. D. hansenii is of great interest within the food industry due to its "salt loving" character, where among other applications, it is used in the ripening process of sausages through the secretion of exopeptidases, development of flavor characteristics and production of cheeses [95][96][97][98][99].…”

Utilization of salt‐rich by‐products from the dairy industry as feedstock for recombinant protein production by Debaryomyces hansenii

“…Many studies have demonstrated that D. hansenii metabolism is enhanced when moderate‐high concentrations of salt (1 M) are found in the media, even though it can tolerate up to 4 M of salt (Breuer & Harms, 2006). Recently, Navarrete, Frost, et al (2021) performed a physiological characterization of D. hansenii in controlled bioreactors testing different salt concentrations (either NaCl or KCl) and assessing cell performance. Moreover, they described a novel survival strategy of this yeast in high salinity environments: when the salt concentration increases from 1 M (optimal for D. hansenii ) to 2 M or more, the yeast changes its metabolism from growing as fast as possible and limiting the nutrients for the competitors, to grow as much as possible and overpopulate the area (Navarrete, Frost, et al, 2021).…”