The methanogenic alkanes-degrading enrichment culture which had been incubated for over 1,300 days amended with n-alkanes (C15–C20) was investigated through clone libraries of bacteria, archaea and assA, mcrA functional genes. These enrichment cultures were obtained from oily sludge after an initial incubation of the oily sludge without any carbon source and then an enrichment transfer with n-alkanes (C15–C20) for acclimation. Activation of alkanes, methane precursor generation and methanogenic pathways are considered as three pivotal stages for the continuous methanogenesis from degradation of alkanes. The presence of functional genes encoding the alkylsuccinate synthase α-subunit indicated that fumarate addition is most likely the one of initial activation step for degradation of n-alkanes. Degradation intermediates of n-alkanes were octadecanoate, hexadecanoate, butyrate, isobutyrate, acetate and propionate, which could provide the appropriate substrates for acetate formation. Both methyl coenzyme M reductase gene and 16S rRNA gene analysis showed that microorganisms of Methanoseata were the most dominant methanogens, capable of using acetate as the electron donor to produce methane. Bacterial clone libraries showed organisms of Anaerolineaceae (within the phylum of Chloroflexi) were predominant (45.5%), indicating syntrophically cooperation with Methanosaeta archaea was likely involved in the process of methanogenic degradation of alkanes. Alkanes may initially be activated via fumarate addition and degraded to fatty acids, then converted to acetate, which was further converted to methane and carbon dioxide by methanogens.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-015-0117-4) contains supplementary material, which is available to authorized users.
Hepatocellular carcinoma (HCC) is the second most common cause of cancer‐related mortality worldwide. The expression of nitric oxide synthase (NOS) and the inhibition of autophagy have been linked to cancer cell death. However, the involvement of serum nitric oxide (NO), the expression of NOS and autophagy have not been investigated in HCC. In the present study, we first established that the NO level was significantly higher in hepatitis B virus‐related HCC than in the liver cirrhosis control (53.60 ± 19.74 vs 8.09 ± 4.17 μmol/L, t = 15.13, P < 0.0001). Using immunohistochemistry, we found that the source of NO was at least partially attributed to the expression of inducible NOS and endothelial NOS but not neuronal NOS in the liver tissue. Furthermore, in human liver cancer cells, NO‐induced apoptosis and inhibited autophagy. Pharmacological inhibition of autophagy also induced apoptosis, whereas the induction of autophagy could ameliorate NO‐induced apoptosis. We also found that NO regulates the switch between apoptosis and autophagy by disrupting the Beclin 1/Vps34 association and by increasing the Bcl‐2/Beclin 1 interaction. Overall, the present findings suggest that increased NOS/NO promotes apoptosis through the inhibition of autophagy in liver cancer cells, which may provide a novel strategy for the treatment of HCC.
Developing eco‐friendly, nonirritant, low‐toxic, and high‐efficient surface active ingredients for detergents is an ongoing challenge in the detergent field. Surfactin is one of the representative lipopeptides produced by microorganisms. In this article, we report the surfactin isolated from cell‐free broth of Bacillus subtilis HSO121 and purified by reversed‐phase high‐performance liquid chromatography for detergent formulations. The biodegradability, acute dermal irritation, acute oral toxicity (LD50 and LC50), surface activity, washing efficiency, and compatibility with hard water of the purified biosurfactant surfactin have been studied to explore the feasibility for applications of the surfactin in detergents. Acute oral toxicity tests (LD50 > 5000 mg kg−1, LC50 > 1000 mg kg−1) and skin irritation tests (PII = 0) indicate that the surfactin is a low‐toxic and nonirritant ingredient for detergent formulation. Moreover, the surfactin shows excellent surface and interfacial properties of emulsification and wettability, high compatibility, and stability in a wide range of temperatures, pH, and hard water and acceptable properties in biodegradability and foaming ability, which suggests that the biosurfactant surfactin is a promising ingredient for detergent formations in our daily life and for industrial applications.
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