Polyhydroxybutyrate production by an extremely halotolerant Halomonas elongata strain isolated from the hypersaline meromictic Fără Fund Lake (Transylvanian Basin, Romania)

Abstract

The tested strain showed the ability for significant production of natural, biodegradable polymers under nutrient limitation and hypersaline conditions suggesting its potentiality for further metabolic and molecular investigations towards enhanced biopolymer production. Additionally, this study reports on the unprecedented use of Raman and XPRD techniques to investigate PHAs of an extremely halotolerant bacterium, thus expanding the repertoire of physical methods to study green plastics derived from extremophilic microorganisms.

Bioplastic (poly-3-hydroxybutyrate) production by the marine bacterium Pseudodonghicola xiamenensis through date syrup valorization and structural assessment of the biopolymer

“…The peaks at 3406 cm −1 showed strong H bond stretching by the terminal OH groups 43 . The spectrum of extracted PHB also showed a band of the C-O stretch corresponding to the C-O group identified at 1278 cm −1 for PHB from H. elongata 23 . Additionally, the bands at 1000-1320 cm −1 were distinctive for the C-O group of the esters 31 .…”

“…The strong band at 1724 cm −1 for carbonyl stretching of the ester group of the extracted PHB is analogous to that for the standard PHB and the peak of the C = O group for PHB from Bacillus cereus 31,43 . FTIR spectra of PHB extracted from H. elongata 23 and S. thermophilus 33 showed C = O stretching vibrations at 1721 cm −1 and 1726 cm −1 , respectively. The FTIR spectra of the PHB extracted from B. sacchari showed strong bands for the carbonyl group of the ester (1720.39 cm −1 ), the band for methyl groups (1379.57 cm −1 ), and the bands for the stretching vibration of methylene and methane groups (1277.68 cm −1 and 2930.54 cm −1 ) 27 .…”

“…These findings may be explained by the accumulation of a high amount of PHB as a survival mechanism depending on bacterial adaptation of the metabolic pathway for osmotic pressure equilibration 49 . Various studies have referred to the stimulation of PHB production as a response to high osmotic pressure for V. proteolyticus 15 , H. elongata 2FF 23 , C. necator 25 , and H. mediterranei 26 . Increasing the salt concentration to higher than the optimal value decreased bacterial growth and therefore PHB accumulation due to the effect of high osmotic stress 14 .…”

“…These results reflected the necessity of monitoring the salinity of the medium to an appropriate extent to prevent high osmotic stress and its effect on growth and PHB production. Various salt concentrations were reported as being optimal for PHB based on the bacterial strains used, such as 1.5% (V. azureus) 17 , 2% (V. harveyi) 14 , 3% (B. subtilis) 50 , 5% (V. proteolyticus) 15 , and 10% (H. elongata) 23 .…”

“…Indeed, the different types of bacterial communities in the Red Sea are reported to be a source of potentially useful bioproducts for biotechnological and pharmaceutical applications, and the gene responsible for PHB synthase exhibits relatively high abundance in the microorganisms living in the Red Sea 19 . The marine bacterial species Vibrio harveyi 14 , Paracoccus species, Micrococcus species 21 , Erythrobacter aquimaris 22 , Halomonas elongata 23 , Bacillus megaterium 24 , Cupriavidus necator 25 , and Haloferax mediterrani 26 have been found to be potent producers of bioplastics. Consequently, Red Sea habitats are regarded as a potential source for novel bacterial strains that exhibit efficient PHB production.…”