Systematic optimization of exopolysaccharide production by Gluconacetobacter sp. and use of (crude) glycerol as carbon source

Comprehensive rheological analysis of structurally related acetan-like heteroexopolysaccharides from two Kozakia baliensis strains in surfactants and galactomannan blends

Natural biopolymers become increasingly attractive as bio-based alternatives to petrol-based rheological modifiers, especially in personal care applications. However, many polysaccharides exhibit undesired properties in cosmetic applications such as limited viscosifying characteristics, unpleasant sensory properties, or incompatibility with certain formulation compounds. Here, a comprehensive rheological analysis of non-decorated acetan-like heteroexopolysaccharides derived from two Kozakia baliensis strains was performed in selected surfactant formulations. The results were compared to native xanthan gum and a genetically engineered xanthan variant, Xan∆gumFGL, which lacks any acetyl- and pyruvyl moieties and whose rheological properties are unaffected by saline environments. All four polysaccharides displayed a highly similar rheological performance in the non-ionic surfactant lauryl glucoside, while the rheological properties differed in amphoteric and anionic surfactants cocamidopropyl betaine and sodium laureth sulfate due to minor changes in side chain composition. Polysaccharide precipitation was observed in the presence of the cationic surfactant. Nevertheless, the native heteroexopolysaccharide derived from K. baliensis LMG 27018 shows significant potential as a salt-independent rheological modifier compared to the genetically engineered Xan∆gumFGL variant. In addition, blends of heteroexopolysaccharides from K. baliensis and several galactomannans displayed synergistic effects which were comparable to native xanthan gum-galactomannan blends. This study shows that heteroexopolysaccharides of K. baliensis are capable of further extending the portfolio of bio-based rheological modifiers.

Exopolysaccharides of Paenibacillus polymyxa: A review

Paenibacillus polymyxa (P. polymyxa) is a member of the genus Paenibacillus, which is a rod-shaped, spore-forming gram-positive bacterium. P. polymyxa is a source of many metabolically active substances, including polypeptides, volatile organic compounds, phytohormone, hydrolytic enzymes, exopolysaccharide (EPS), etc. Due to the wide range of compounds that it produces, P. polymyxa has been extensively studied as a plant growth promoting bacterium which provides a direct benefit to plants through the improvement of N fixation from the atmosphere and enhancement of the solubilization of phosphorus and the uptake of iron in the soil, and phytohormones production. Among the metabolites from P. polymyxa, EPS exhibits many activities, for example, antioxidant, immunomodulating, anti-tumor and many others. EPS has various applications in food, agriculture, environmental protection. Particularly, in the field of sustainable agriculture, P. polymyxa EPS can be served as a biofilm to colonize microbes, and also can act as a nutrient sink on the roots of plants in the rhizosphere. Therefore, this paper would provide a comprehensive review of the advancements of diverse aspects of EPS from P. polymyxa, including the production, extraction, structure, biosynthesis, bioactivity and applications, etc. It would provide a direction for future research on P. polymyxa EPS.

Acetan-like heteropolysaccharide production by various Kozakia baliensis strains: Characterization and further insights

The family of Acetobacteraceae has demonstrated their ability to produce several heteropolysaccharides with a strong structural resemblance to xanthan gum. In this study, we assessed the potential of three isolates of K. baliensis as exopolysaccharide producers, namely K. baliensis SR-745, K. baliensis LMG 27018, and K. baliensis SR-1290. Among these, K. baliensis SR-745 was identified as the most promising candidate, exhibiting a final exopolysaccharide titer of 7.09 (± 0.50) g·L-1 and a productivity of 0.15 (± 0.01) g·L-1·h-1. Subsequent monomer analysis confirmed structural variations for the side chain composition of different strains. A molar subunit ratio of 6:1:1:1 (d-glucose: D-mannose: D-galactose: D-glucuronic acid) for EPS derived from K. baliensis SR-745 and of 3:1:3:1 for K. baliensis LMG 27018 was determined, while the exopolysaccharide produced by K. baliensis SR-1290 consisted of a major share of rhamnose. In-depth rheological polymer characterizations revealed high viscosity rates and predominantly elastic gel character, making polysaccharides of K. baliensis highly interesting for applications in the food and cosmetic industry. Further insights into the fundamental structure-function relationships of biopolymers were obtained by comparing exopolysaccharides derived from K. baliensis to a genetically engineered xanthan variant lacking acetyl and pyruvyl substitutions.

Biodegradation of emerging organic pollutant gemfibrozil: Mechanism, kinetics and pathway modelling

The increasing population has raised the demand for pharmaceutical and personal care products to maintain a good health. Gemfibrozil (GEM), is extensively used as a lipid regulator and is frequently detected in wastewater treatment systems and poses deleterious health and ecological effects. Hence, the current study employing Bacillus sp. N2 reports the degradation of gemfibrozil via co-metabolism in 15 days. The study reported 86 % degradation with GEM (20 mgL^-1) using sucrose (150 mgL^-1) as a co-substrate; as compared to 42 % without a co-substrate. Further, time-profiling studies of metabolites revealed significant demethylation and decarboxylation reactions during degradation that leads to formation of six (M1, M2, M3, M4, M5, M6) metabolites as by-products. Based on the LC-MS analysis a potential degradation pathway for GEM by Bacillus sp. N2 was proposed. The degradation of GEM has not been reported so far and the study envisages eco-friendly approach to tackle pharmaceutical- active- compounds.

Acetobacteraceae as exopolysaccharide producers: Current state of knowledge and further perspectives

Exopolysaccharides formation against harmful biotic and abiotic environmental influences is common among bacteria. By using renewable resources as a substrate, exopolysaccharides represent a sustainable alternative to fossil-based polymers as rheological modifiers in food, cosmetics, and pharmaceutical applications. The family of Acetobacteraceae, traditionally associated with fermented food products, has demonstrated their ability to produce a wide range of structural and functional different polymers with interesting physicochemical properties. Several strains are well known for their production of homopolysaccharides of high industrial importance, such as levan and bacterial cellulose. Moreover, some Acetobacteraceae are able to form acetan-like heteropolysaccharides with a high structural resemblance to xanthan. This mini review summarizes the current knowledge and recent trends in both homo- and heteropolysaccharide production by Acetobacteraceae.

Biosynthesis of exopolysaccharide from waste molasses using Pantoea sp. BCCS 001 GH: a kinetic and optimization study

The bacterium Pantoea sp. BCCS 001 GH produces an exopolysaccharide (EPS) named Pantoan through using sugar beet molasses (SBM) as an inexpensive and widely available carbon source. This study aims to investigate the kinetics and optimization of the Pantoan biosynthesis using Pantoea sp. BCCS 001 GH in submerged culture. During kinetics studies, the logistic model and Luedeking–Piret equation are precisely fit with the obtained experimental data. The response surface methodology (RSM)-central composite design (CCD) method is applied to evaluate the effects of four factors (SBM, peptone, Na₂HPO₄, and Triton X-100) on the concentration of Pantoan in batch culture of Pantoea sp. BCCS 001 GH. The experimental and predicted maximum Pantoan production yields are found 9.9 ± 0.5 and 10.30 g/L, respectively, and the best prediction factor concentrations are achieved at 31.5 g/L SBM, 2.73 g/L peptone, 3 g/L Na₂HPO_4, and 0.32 g/L Triton X-100 after 48 h of submerged culture fermentation, at 30 °C. The functional groups and major monosaccharides (glucose and galactose) of a purified Pantoan are described and confirmed by ¹HNMR and FTIR. The produced Pantoan is also characterized by thermogravimetric analysis and the rheological properties of the biopolymer are investigated. The present work guides the design and optimization of the Pantoea sp. BCCS 001 GH culture media, to be fine-tuned and applied to invaluable EPS, which can be applicable in food and biotechnology applications.