Chemical structure and antioxidant activity of a new exopolysaccharide produced from Micrococcus luteus

Exopolysaccharides synthesized by lactic acid bacteria: biosynthesis pathway, structure-function relationship, structural modification and applicability

Probiotics and their fermentation products are increasingly been focused on due to their health-boosting effects. Exopolysaccharides (EPS) synthetized by lactic acid bacteria (LAB) are widely applied as texture modifiers in dairy, meat and bakery products owning to their improved properties. Moreover, LAB-derived EPS have been confirmed to possess diverse physiological bioactivities including antioxidant, anti-biofilm, antiviral, immune-regulatory or antitumor. However, the low production and high acquisition cost hinder their development. Even though LAB-derived EPS have been extensively studied for their production-improving, there are only few reports on the systematic elucidation and summary of the relationship among biosynthesis pathway, strain selection, production parameter, structure-function relationship. Therefore, a detailed summary on biosynthesis pathway, production parameter and structure-function relationship of LAB-derived EPS is provided in this review, the structural modifications together with the current and potential applications are also discussed in this paper.

Cliona varians-Derived Actinomycetes as Bioresources of Photoprotection-Related Bioactive End-Products

Sunscreen and sunblock are crucial skincare products to prevent photoaging and photocarcinogenesis through the addition of chemical filters to absorb or block ultraviolet (UV) radiation. However, several sunscreen and sunblock ingredients, mostly UV filters, have been associated with human and environmental safety concerns. Therefore, the exploration and discovery of promising novel sources of efficient and safer compounds with photoprotection-related activities are currently required. Marine invertebrates, particularly their associated microbiota, are promising providers of specialized metabolites with valuable biotechnological applications. Nevertheless, despite Actinobacteria members being a well-known source of bioactive metabolites, their photoprotective potential has been poorly explored so far. Hence, a set of methanolic extracts obtained from Cliona varians-derived actinomycetes was screened regarding their antioxidant and UV-absorbing capacities (i.e., photoprotection-related activities). The active extract-producing strains were identified and classified within genera Streptomyces, Micrococcus, Gordonia, and Promicromonospora. This is the first report of the isolation of these microorganisms from C. varians (an ecologically important Caribbean coral reef-boring sponge). The in vitro cytotoxicity on dermal fibroblasts of oxybenzone and the selected active extracts revealed that oxybenzone exerted a cytotoxic effect, whereas no cytotoxic effect of test extracts was observed. Accordingly, the most active (SPFi > 5, radical scavenging > 50%) and nontoxic (cell viability > 75%) extracts were obtained from Streptomyces strains. Finally, LC-MS-based characterization suggested a broad chemical space within the test strains and agreed with the reported streptomycetes' chemodiversity. The respective metabolite profiling exposed a strain-specific metabolite occurrence, leading to the recognition of potential hits. These findings suggest that marine Streptomyces produce photoprotectants ought to be further explored in skincare applications.

Effect of polysaccharide from Bacillus subtilis sp. on cardiovascular diseases and atherogenic indices in diabetic rats

BACKGROUND

Diabetes mellitus induces chronic complications such as cardiovascular damage, cataracts and retinopathy, nephropathy, and polyneuropathy. The main aim of the study was to isolate and identify both of bacterial strain and exopolysaccharide to assess the possible efficiency of exopolysaccharide (BSEPS) from Bacillus subtilus sp .suppress on cardiovascular diseases, atherogenic and coronary risk indices in diabetic rats.

METHODS

The bacterial strain used was isolated from mangrove tree sediment by serial dilution and the spread-plate technique and identified by morphological, physiological, and biochemical characteristics, and by 16S rRNA analysis. The BSEPS was extracted from the bacterial supernatant by four volumes child ethanol then the functional groups, MW and chemical analysis were detected by Fourier-transform infrared (FTIR), gel permeation chromatograph (GPC) and High-performance liquid chromatography (HPLC). Also an antioxidant activity was measured by using 2,2-diphenyl-1-picrylhydrazyl (DPPH). Thirty-two male Sprague-Dawley rats were equally randomized into four groups: control group supplemented with normal saline (Group I); the second group supplemented with BSEPS (Group II); diabetic group supplemented with normal saline (Group III) and the diabetic group supplemented with BSEPS (Group IV). Diabetes was induced by Streptozotocin (STZ) (65 mg/kg BW) intraperitoneally. BSEPS (100 mg/kg BW) was administered orally for four weeks, following STZ induction.

RESULTS

The isolated strain was identified based on 16S rRNA sequence as Bacillus subtilis sp. suppress. A preliminary chemical analysis of BSEPS indicated that the monosaccharides were mannuronic acid, glucuronic acid, glucose, galactose, and mannose in a molar ratio of 1.6:1.5:1.0:2.3:1.4, respectively, with a molecular weight of 1.66 × 10(4) g mol(-1) and a molecular number of 7.64 × 10(3) g mol(-1). BSEPS inhibited 2,2-diphenyl-1-picrylhydrazyl radical activity, and BSEPS supplement reduced glucose (p < 0.05) and troponin levels while insulin levels increased (p < 0.05). BSEPS also reduced total serum cholesterol, low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), and triglycerides, and elevated high-density lipoprotein-cholesterol (HDL). In parallel, intercellular adhesion molecule (ICAM), and vascular cell adhesion molecule (VCAM) levels in STZ-induced diabetic rats were reduced. Moreover, polysaccharides reduced atherogenic and coronary risk indices, which were confirmed by histopathological examination of the heart and aorta.

CONCLUSIONS

Our study suggests that BSEPS improves hyperglycemia, dyslipidemia, and cardiovascular disease risk in STZ-induced diabetic rats.