The saltern-derived Paludifilum halophilum DSM 102817T is a new high-yield ectoines producer in minimal medium and under salt stress conditions

Abstract

In the present study, the growth conditions and accumulation of ectoines (ectoine and hydroxyectoine) by Paludifilum halophilum DSM 102817 T under salt stress conditions have been investigated. The productivity assay of this strain for ectoines revealed that the highest cellular content was reached in the minimal glucose sea water medium (SW-15) within 15% salinity. The addition of 0.1% (w/v) aspartic acid to the medium allowed an average of four times higher biomass production, and a dry mycelial biomass of 1.76 g L −1 was obtained after 6 days of growth in shake flasks at 40 °C and 200 rpm. Among the inorganic cations supplemented to the glucose SW-15 medium, the addition of 1 mM Fe 2+ yielded the highest amount of mycelial biomass (3.45 g L −1 ) and total ectoines content (119 mg g −1 ), resulting in about 410 mg L −1 of products at the end of exponential growth phase. After 1 h of incubation in an osmotic downshock solution containing 2% NaCl, 70% of this content was released by the mycelium, and recovering cells maintained a high survival, with a maximal growth rate (µ max ) of about 93% of the control population exposed to 15% NaCl. During growth at optimal salinity and temperature (15% NaCl and 40 °C), P. halophilum developed a compact and circular pellets that were easy to separate by simple decantation from both fermentation media and after hypoosmotic shock. Overall, the ectoines excreting P. halophilum could be a promising resource for ectoines production in a commercially valuable culture medium and at a large-scale fermentation process.

Genome analysis of the salt-resistant Paludifilum halophilum DSM 102817T reveals genes involved in flux-tuning of ectoines and unexplored bioactive secondary metabolites

“…Such a challenging habitat requires active measures by this halophile to counteract the out ow of water from the cells and to optimize the solvent properties of the cytoplasm for biochemical reactions and the functionality of cell components (Czech et al 2018a). Analysis of the physiological response of P. halophilum revealed that this bacterium uses the salt-out strategy through the accumulation of ectoines at relatively high yields (Ayadi et al 2020). The data presented here support this conclusion and highlight the ability of P. halophilum to cope with a broad spectrum of salinities ranging from 5 to 20 %.…”

“…Strain culture conditions P. halophilum DSM 102817 T was routinely cultivated in an optimized mineral sea water (SW) medium (Ayadi et al 2020) aspartic acid. The pH of the growth medium was adjusted to 8.3-8.4 with 4 M NaOH, and the osmolarity the the set-up of the individual experiments by adding NaCl.…”

“…Paludi lum halophilum strain SMBg3 is a salt and heat-resistant bacteria from the family of Thermoactinomycetaceae from the phylum Actinobacteria (Jiang et al 2019). It was isolated from Sfax solar saltern sediment in Tunisia (Frikha-Dammak et al 2016) and has shown be a high-yield ectoines producers under salt stress conditions (Ayadi et al 2020). Here, we report the genome sequencing of the strain and genetic information on genes involved in ectoines and secondary metabolites synthesis.…”