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Saline environments are extreme habitats with a high diversity of microorganisms source of a myriad of biomolecules. These microorganisms are assigned as extremophiles recognized to be producers of new natural compounds, which can be synthesized by helping to survive under harshness and extreme conditions. In Brazil, in the saline and semi-arid region of Areia Branca (Caatinga biome), halotolerant bacteria (able to growth at high NaCl concentrations) were isolated from rhizosphere of native plants Blutaparon portulacoides and Spergularia sp. and their biopolymer production was studied. A total of 25 bacterial isolates were identified at genus level based on 16S rRNA gene sequence analysis. Isolates were mainly Gram-positive bacteria from Bacillaceae, Staphylococcaceae, Microbacteriaceae, and Bacillales XII incertae sedis families, affiliates to Bacillus, Staphylococcus, Curtobacterium, and Exiguobacterium genera, respectively. One of the Gram-negative isolates was identified as member of the Pseudomonadaceae family, genus Pseudomonas. All the identified strains were halotolerant bacteria with optimum growth at 0.6-2.0 M salt concentrations. Assays for biopolymer production showed that the halotolerant strains are a rich source of compounds as polyhydroxyalkanoates (PHA), biodegradable biopolymer, such as poly(3-hydroxybutyrate) (PHB) produced from low-cost substrates, and exopolysaccharides (EPS), such as hyaluronic acid (HA), metabolite of great interest to the cosmetic and pharmaceutical industry. Also, eight bacterial EPS extracts showed immunostimulatory activity, promising results that can be used in biomedical applications. Overall, our findings demonstrate that these biomolecules can be produced in culture medium with 0.6-2.0 M NaCl concentrations, relevant feature to avoid costly production processes. This is the first report of biopolymer-producing bacteria from a saline region of Caatinga biome that showed important biological activities.

Sulfated polysaccharides (SP) are a complex group of bioactive molecules able to inhibit tumor growth. SP increase the effectiveness of chemotherapy and reduce some side effects. Brown algae produce SP with several biological activities including antitumor. This work aimed to investigate the antitumor effect of SP from the brown algae Dictyota caribaea (Dc-SP). Dc-SP were extracted with proteolytic enzyme and supernatant was precipitated with increasing concentrations of ethanol.Antiproliferative activity of Dc-SP was tested by the MTT assay against colon cancer (HCT 116) and metastatic melanoma (B16-F10) cell lines. The antitumor effect was evaluated on Swiss mice transplanted with sarcoma 180 tumor and treated i.p. during 7 days with saline or Dc-SP (25 and 50 mg/kg/animal). Dc-SP did not exhibit cytotoxicity in vitro, however the Dc-SP-treated mice depicted up to 50% tumor growth inhibition. Dc-SP treatment induced spleen weight increasing along with intense white pulp disorganization. Furthermore Dc-SP did not depict hepatic toxicity, nephrotoxicity nor leukopenia and did induce increase of platelets count. Altogether, these results represent a promising antitumor host dependent effect induced by Dc-SP.

Fucoidans are sulfated polysaccharides capable of exerting biological activities such as antitumor and immunomodulatory effects. Previous studies demonstrated the antitumor activity of non-cytotoxic fucoidan from the seaweedDictyota caribaea(Dc-SP)in vivo. Macrophages (Mφ) are innate immune cells capable of promoting or inhibiting tumor growth depending on the stimulus. This study aimed to evaluate the immunostimulant activity of Dc-SP on murine Mφ (RAW264.7)in vitro. Dc-SP was assessed for its ability to modify cell viability and stimulate the production of antitumor markers on RAW264.7 cells. Dc-SP induced an increase (p<0.05) in the production of NO and cytokines TNF-α, IL-1β, and IL-10. The exposure of Mφ to Dc-SP also increased (p<0.05) the expression of M1 macrophage markers such as iNOS, CD86, and MHC II. The antiproliferative activity of RAW264.7 cells stimulated with DC-SP on melanoma cells (B16-F10)in vitro. Dc-SP did not exhibit direct cytotoxicity on B16-F10, however, the conditioned medium (CM) of RAW264.7 previously stimulated with Dc-SP (CM-Dc-SP) showed antiproliferative activity on tumor cells. B16-F10 incubated with CM-Dc-SP showed a cytostatic profile, tumor cells did not alter membrane integrity, however, suffered morphological changes such as cell shrinkage and high granularity. In conclusion, Dc-SP stimulated Mφ to an antitumor phenotype.