Lactococcus lactis is a probiotic bacterium that produces various bacteriocins. Periodontopathogens induce inflammation and halitosis through the actions of lipopolysaccharide (LPS) and trypsin-like enzymes. The purpose of this study was to investigate the inhibitory effects of L. lactis on the bioactivity of periodontopathogens. To investigate the antimicrobial peptide of L. lactis, the spent culture medium (SCM) of L. lactis was treated with or without proteinase K after collection by centrifugation, and the antibacterial activity of SCM against periodontopathogens was assessed. To evaluate the neutralizing effect of L. lactis on halitosis, SCM of periodontopathogens was mixed with an L. lactis suspension, and the levels of volatile sulfur compounds (VSCs) were measured by gas chromatography. LPS from the periodontopathogens was extracted by an LPS extraction kit with little modification, and THP-1 cells as a monocytic cell line were treated with the extracted LPS in the presence or absence of UV-killed L. lactis. The production of inflammatory cytokines was analyzed by ELISA. The SCM of L. lactis exhibited antimicrobial activity against the periodontopathogens, whereas the proteinase K-treated SCM showed little antimicrobial activity. In addition, the L. lactis suspension had a neutralizing effect on the VSCs produced by periodontopathogens, and UV-killed L. lactis inhibited the production of IL-6 and TNF-α induced by the LPS. These results suggest that L. lactis may be a useful probiotic to prevent and treat periodontitis and halitosis.
A new antibiotic, designated mumiamicin, was isolated from the cultured broth of the rare actinomycete strain, Mumia sp. YSP-2-79, by Diaion HP-20, silica gel and ODS column chromatography, followed by HPLC purification. The chemical structure of mumiamicin was elucidated as a new furan fatty acid by nuclear magnetic resonance and mass spectrometry. Mumiamicin showed antimicrobial activity and antioxidative activity.
Bilirubin oxidase has applications in the health and environmental sectors. Hence, several attempts have been made to increase enzyme yields. However, improvements were not very high. We report here the development of a mutant strain of Myrothecium verrucaria by using UV-rays, which produced 28.8 times more enzyme compared with the parent and was higher than the yields reported in earlier submerged cultures. The mutant strain produced 35.6 times more enzyme than the parent in solid-state fermentation, which is better than that previously reported for a solid-state fermentation process. The specific activity of the enzyme produced by the mutant was higher than that of the parental enzyme. Bilirubin oxidase from both strains showed an optimum activity at pH 7 and 40°C. However, the time required to inactivate half of the initial enzyme activity at 60°C was much higher in the case of the enzyme obtained from the mutant compared with the parental enzyme. The improved thermostability of the enzyme from the mutant strain could be due to the point mutations induced during the UV irradiation, since there was no change in the mass of the enzyme compared with the parental enzyme. The bilirubin oxidase of the mutant strain degraded the bilirubin faster than the enzyme obtained from the parent under similar conditions. Faster activity of the enzyme obtained from the mutant strain could be due to its lower Km (79.4 μM) compared with that of the parental enzyme (184 μM). Hence, the mutant enzyme showed a better functionality and thermostability, which will be beneficial for industrial applications.
Saccharomyces cerevisiae Ypr147cp was found localized to lipid droplets but the physiological role of Ypr147cp remains unknown. Sequence analysis of Ypr147cp revealed an α/β hydrolase domain along with the conserved GXSXG lipase motif. Recombinant Ypr147cp showed both triacylglycerol lipase and ester hydrolase activities. Knock out of YPR147C led to accumulation of TAG in ypr147cΔ when compared to wild type (WT). In addition, transmission electron microscopic analysis of ypr147cΔ cells revealed a greater number of lipid bodies, justifying the increase in TAG content, and the phenotype was rescued upon overexpression of YPR147C in ypr147cΔ. Moreover, the lipid profiling confirmed the accumulation of fatty acids derived from neutral and phospholipids in ypr147cΔ cells. Based on these results, Ypr147cp is identified as a lipid droplet associated triacylglycerol lipase along with an ester hydrolyzing capacity.
γ-aminobutyric acid (GABA) is an important non-protein amino acid involved in the response to various environmental stresses in plant cells. The objectives of this study was to test the hypothesis that intracellular accumulation of GABA improves osmotic tolerance in the unconventional yeast Candida glycerinogenes. In C. glycerinogenes, the expression of UGA4 encoding GABA-specific permease is highly induced by hyperosmotic stress. Exogenous GABA application enhanced intracellular GABA accumulation and promoted cell growth under hyperosmotic conditions. Overexpression of the glutamate decarboxylase gene GAD1 resulted in an increased intracellular GABA and improvement in cell growth under hyperosmotic conditions. These results indicated that improving intracellular GABA accumulation of C. glycerinogenes, either through exogenous application or cellular synthesis, is available for improving the tolerance to hyperosmotic stress. We demonstrate that GABA accumulation plays an important role in osmotic stress resistance of the unconventional yeast C. glycerinogenes.