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CpG islands are typically located in the 5′ end of genes and considered as gene markers because they play important roles in gene regulation via epigenetic change. In this study, we compared the features of CpG islands identified by several major algorithms by setting the parameter cutoff values in order to obtain a similar number of CpG islands in a genome. This approach allows us to systematically compare the methylation and gene expression patterns in the identified CpG islands. We found that Takai and Jones' algorithm tends to identify longer CpG islands but with weaker CpG island features (e.g., lower GC content and lower ratio of the observed over expected CpGs) and higher methylation level. Conversely, the CpG clusters identified by Hackenberg et al.'s algorithm using stringent criteria are shorter and have stronger features and lower methylation level. In addition, we used the genome-wide base-resolution methylation profile in two cell lines to show that genes with a lower methylation level at the promoter-associated CpG islands tend to express in more tissues and have stronger expression. Our results validated that the DNA methylation of promoter-associated CpG islands suppresses gene expression at the genome level.

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An alkaline lipase strain of Pseudomonas aeruginosa HFE733 was isolated from soil samples of domestic waste. The alkaline lipase from P. aeruginosa HFE733 was purified and characterized. The enzyme was purified 9.97-fold by means of ammonium sulphate precipitation, Sephadex G-25 and diethylaminoethyl (DEAE) cellulose chromatography. Purified alkaline lipase protein was analyzed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), the molecular mass was 51.0 kDa. The enzyme exhibited maximum activity at 40 C and pH 8.5. The enzyme is stable at pH 7.0-8.5. It was remarkably activated by some metal ions and chemical reagents, such as Fe 3+ , Al 3+ , b-mercaptoethanol, cysteine, DL-dithiothreitol (DTT), Tween 80 and Triton X-100, but suppressed by sodium dodecyl sulfate (SDS) at 10 mmol/L. The P. aeruginosa HFE733 strain and lipase exhibited remarkable potential for biodegradation of oil and organics (measured as chemical oxygen demand (COD)). We demonstrated that it can be used for biodegradation of food wastewater from restaurants.

The purification and characterization of the extracellular polygalacturonase from V25 submerged culture using orange peel waste were investigated. This polygalacturonase, with a molecular weight of 75.28 kDa, was purified to 16.89 purification fold with a recovery of 18.46% and specific activity of 2469.77 U/mg protein by ammonium sulfate precipitation, DEAE cellulose chromatography, and Sephadex G-100 gel filtration. The enzyme exhibited maximum activity at 60°C and pH 5.0 and was stable over a wide range of pH levels (3.0-11.0). Moreover, enzyme activity was enhanced by Cu and cysteine, whereas it was strongly inhibited by Hg. The extent of enzymatic hydrolysis was negatively correlated with the degree of pectin esterification. K and V values of the polygalacturonase were 5.44 mg/mL and 61.73 μmol/(min·mg), respectively. The polygalacturonase was applied in the juice clarification of four fruits, and results showed that the percentage transmittance at 660 nm increased by 3.51, 4.36, 8.04, and 12.2%.