Exopolysaccharide from Bacillus mojavensis DAS10-1; Production and Characterization

Exploring biosynthesis strategies to boost the yield of exopolysaccharide-protein blend from Bacillus arachidis SY8(T), an isolated native strain, as a potent adsorbent for heavy metals removal

This investigation centers on the synthesis of a polysaccharide-protein blend produced by an isolated native strain (99.12 % phylogenetic affinity with Bacillus arachidis SY8(T)). The primary objective was to investigate the production of extracellular polymeric substances (EPS) under diverse stress conditions, encompassing exposure to heavy metal ions, salt, and toxic agents. Additionally, the impact of environmental parameters, namely pH, inoculation percentage, and time, on the production was investigated. Subsequently, the study examined the biosorption potential of the EPS produced for Pb(II), Cu(II), and Mn(II). The EPS obtained was thoroughly characterized via various tests. Rheological evaluations of an EPS solution (2 wt%) confirmed its pseudo-plastic and non-Newtonian fluid properties, while TGA analysis demonstrated its thermal stability up to 600 °C. Additional analyses, including GPC, FTIR, and H-NMR, provide further insights into the produced EPS. The best conditions for EPS production are determined: 5 % NaCl salt, serving as an effective stress inducer, and 37 °C, pH 6, with a 5 % inoculation, over 96 h. EPS demonstrates remarkable removal efficiencies of 99.9, 99.4 and 78.9 % for Pb(II), Cu(II), and Mn(II), respectively. These findings highlight the potential of EPS as an effective agent for removing heavy metal ions.

Advanced strategies for metabolic engineering of Bacillus to produce extracellular polymeric substances

Extracellular polymeric substances are mainly synthesized via a variety of biosynthetic pathways in bacteria. Bacilli-sourced extracellular polymeric substances, such as exopolysaccharides (EPS) and poly-γ-glutamic acid (γ-PGA), can serve as active ingredients and hydrogels, and have other important industrial applications. However, the functional diversity and widespread applications of these extracellular polymeric substances, are hampered by their low yields and high costs. Biosynthesis of extracellular polymeric substances is very complex in Bacillus, and there is no detailed elucidation of the reactions and regulations among various metabolic pathways. Therefore, a better understanding of the metabolic mechanisms is required to broaden the functions and increase the yield of extracellular polymeric substances. This review systematically summarizes the biosynthesis and metabolic mechanisms of extracellular polymeric substances in Bacillus, providing an in-depth understanding of the relationships between EPS and γ-PGA synthesis. This review provides a better clarification of Bacillus metabolic mechanisms during extracellular polymeric substance secretion and thus benefits their application and commercialization.

Exopolysaccharide of Anoxybacillus pushchinoensis G11 has antitumor and antibiofilm activities

Exopolysaccharides (EPS/EPSs) possess several various applications in the food and pharmaceutical industries. This study was performed to investigate the biological (antibiofilm and antitumor), rheological (temperature, shear rate, and density) and chemical (solubility, carbohydrate and protein content, composition, molecular weight, functional group analysis, thermal analysis, X-ray diffraction pattern and scanning electron microscopy) properties of the EPS, which was purified from the locally isolated thermophilic bacterium Anoxybacillus pushchinoensis G11 (MN720646). EPS was found to have antibiofilm and antitumor [lung (A-549) and colon (Caco-2 and HT-29) cancer] activities. The viscosity of EPS showing Newtonian flow was temperature dependent. As chemical properties, the EPS was found to be a heteropolysaccharide containing arabinose (57%), fructose (26%), glucose (12%), and galactose (5%). EPS contained 93% carbohydrates and 1.08% protein. The molecular weight of EPS was determined as 75.5 kDa. The FTIR analysis confirmed the presence of sulfate ester (band at 1217 cm^-1), an indication of the antitumor effect. The EPS was semi-crystalline. It could maintain 36% of its weight at 800 °C and crystallization and melting temperatures were 221 and 255.6 °C. This is the first report on the EPS production potential and the biological activity of A. pushchinoensis.

Structural elucidation and interfacial properties of a levan isolated from Bacillus mojavensis

A strain with high exopolysaccharide (EPS) production was isolated from soil and identified as Bacillus mojavensis based on the 16S rRNA gene sequencing and biochemical properties. The EPS produced simultaneously with the growth phase reached a maximum of 22 g/L after attaining a stationary phase with sucrose used as sole carbon source. B. mojavensis EPS (BM-EPS) was recovered, fractionated by ethanol precipitation and analysed by NMR and methylation analyses. The BM-EPS was found to be composed of (β2 → 6)-Fruf residues, characteristic of a levan, with an average molecular weight of 2.3 MDa. A homogeneous micro-porous and rough structure matrix was observed by SEM of the freeze-dried powdered sample. A concentration-dependent water-soluble nature was observed, with good water (5.3 g/g) and oil (36 g/g) holding capacities. The levan displayed good emulsification activity with excellent stability against food grade oil, thus favoring it as a promising emulsifying agent to food industries.