Exopolysaccharides Production by Cultivating a Bacterial Isolate from the Hypersaline Environment of Salar de Uyuni (Bolivia) in Pretreatment Liquids of Steam-Exploded Quinoa Stalks and Enzymatic Hydrolysates of Curupaú Sawdust

Abstract

The halotolerant bacterial strain BU-4, isolated from a hypersaline environment, was identified as an exopolysaccharide (EPS) producer. Pretreatment liquids of steam-exploded quinoa stalks and enzymatic hydrolysates of Curupaú sawdust were evaluated as carbon sources for EPS production with the BU-4 strain, and the produced EPS was characterized using FTIR, TGA, and SEM. Cultivation was performed at 30 °C for 48 h, and the cells were separated from the culture broth by centrifugation. EPS was isolated from the cell pellets by ethanol precipitation, and purified by trichloroacetic acid treatment, followed by centrifugation, dialysis, and freeze-drying. EPS production from quinoa stalks- and Curupaú sawdust-based substrates was 2.73 and 0.89 g L−1, respectively, while 2.34 g L−1 was produced when cultivation was performed on glucose. FTIR analysis of the EPS revealed signals typical for polysaccharides, as well as ester carbonyl groups and sulfate groups. High thermal stability, water retention capacity and gel-forming ability were inferred from SEM and TGA. The capability of the halotolerant isolate for producing EPS from pretreatment liquids and hydrolysates was demonstrated, and characterization of the EPS revealed their broad application potential. The study shows a way for producing value-added products from waste materials using a bacterium from a unique Bolivian ecosystem.

Residual Brewing Yeast as Substrate for Co-Production of Cell Biomass and Biofilm Using Candida maltosa SM4

“…Images taken at different magnifications confirmed the film-like pattern of the obtained product. The continuous and glittering surface and the compact structure observed have a similar appearance as that of other previously described microbial biofilms [31,32], and it is different from the rather grainy and discontinuous texture revealed by SMS imaging of non-film forming biopolymers [29].…”

“…Based on previously used methodologies [29], the culture broth was centrifuged at 3000 g for 15 min at 4 • C, the cell pellet was discarded, and the cell-free supernatant was treated with ethanol for biofilm precipitation. Three volumes of 99.5% ethanol were added to the supernatant, and the mixture was stored overnight at 4 • C in bottles to allow precipitation of the extracellular polymer.…”

Extraction of the Bacterial Extracellular Polysaccharide FucoPol by Membrane-Based Methods: Efficiency and Impact on Biopolymer Properties

“…All extracted FucoPol samples displayed similar TGA curves, with two main degradation steps ( Figure 5 ). The first degradation step, corresponding to weight losses of 8–12%, occurred between around 36 and 137 °C and is related to the elimination of water molecules physically entrapped or/and adsorbed to the polysaccharide through hydrogen bonding [ 45 , 46 ]. Samples F-1 100 and F-1 30 had the lowest weight loss values at this temperature range (10 and 8%, respectively), suggesting they had lower contents of adsorbed water compared to the samples obtained by Methods 2 and 3 that displayed the same weight loss (12%).…”

Production of Exopolysaccharides by Cultivation of Halotolerant Bacillus atrophaeus BU4 in Glucose- and Xylose-Based Synthetic Media and in Hydrolysates of Quinoa Stalks

“…In a recent study, we reported an EPS-producing halotolerant bacterial strain isolated from Salar de Uyuni, which is a salt desert at 3600 m a.s.l. in the Altiplano [13]. The study provided some initial input, but further efforts were required to clarify the biotechnological potential of the bacterial isolate and to explore application possibilities of the produced EPS.…”