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A simple, sensitive and inexpensive method has been developed for the quantitative determination of eight polycyclic aromatic hydrocarbons (PAHs) in vegetables based on headspace solid-phase microextraction coupled with gas chromatography using a sol-gel calix[6]arenecontaining fiber. Parameters related to the extraction efficiency such as extraction temperature, extraction time, ionic strength, stirring speed, and solvents' addition were evaluated and optimized. Owing to the good selectivity and high extraction capability of the sol-gel calix[6]arene-containing fiber, low detection limits of 0.04-2.32 ng g -1 and good linearities with linear correlation coefficients[0.9964 were obtained. The relative standard deviation values were \11.6% for all of the PAHs. Average recoveries ranged from 81.07 to 107.5%. The method was applied to analyze nine kinds of vegetables near South Lake, Wuhan, China. The total concentrations of PAHs in these vegetables were found to vary between 3.91 and 96.98 ng g -1 wet weight with 2-and 3-ring PAHs predominating. Generally speaking, PAHs levels in leafy vegetables were higher than those in fruit vegetables, and root and subterranean stem vegetables had the lowest levels. The effect of cooking methods on PAHs concentration in vegetables was tested, and the results showed that PAHs in vegetables reduced a little after blanching, and was not detected after stir-frying.

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Among the protease-producing bacterial strains isolated from deep-sea sediments, SWJS2 was finally selected and identified as genus Exiguobacterium. Plackett-Burman and orthogonal array designs were applied to optimize the fermentation conditions, and the results are as follows: Glucose 5g, yeast extract 15g, glycerin 2g and CaCl2 ⋅2H2 O 0.5 g dissolved in 1 L artificial seawater; temperature 25 °C, original pH 7, inoculum rate 2%, seed age 12 H, loading volume 25 mL (250-mL Erlenmeyer flask), shaking speed 150 rpm, and fermentation time 44 H. The protease activity production was improved from about 80 to 660 U/mL under the optimized parameters. The protease was purified fourfold with specificity activity of 30,654.1 U/mg protein and a total yield of 16.2%. The protease exhibited the maximum activity at 40-45 °C and pH 7. Moreover, the enzyme activity was found to be inhibited by Cu(2+) , Ba(2+) , Cd(2+) , Hg(2+) , and Al(3+) at 5 mM, whereas it can be increased by Mg(2+) , Mn(2+) , and Ca(2+) at 0.5-5 mM. The enzyme was totally inactivated by 1 or 5 mM ethylenediaminetetraacetic acid but not by phenylmethanesulfonyl fluoride, tyrpsin inhibitor from Glycine max (STI), benzamidine, 5,5'-dithio-bis-(2-nitro benzoic acid), or pepstatin A, suggesting that it belonged to metalloprotease.

We applied near-infrared (NIR) spectroscopy with chemometrics for the rapid and reagent-free analysis of serum urea nitrogen (SUN). The modeling is based on the average e®ect of multiple sample partitions to achieve parameter selection with stability. A multiparameter optimization platform with Norris derivative¯lter-partial least squares (Norris-PLS) was developed to select the most suitable mode ðd ¼ 2, s ¼ 33, g ¼ 15Þ. Using equidistant combination PLS (EC-PLS) with four parameters (initial wavelength I, number of wavelengths N, number of wavelength gaps G and latent variables LV), we performed wavelength screening after eliminating highabsorption wavebands. The optimal EC-PLS parameters were I ¼ 1228 nm, N ¼ 26, G ¼ 16 and LV ¼ 12. The root-mean-square error (SEP), correlation coe±cient ðR P Þ for prediction and ratio of performance-to-deviation (RPD) for validation were 1.03 mmol L À1 , 0.992 and 7.6, respectively. We proposed the wavelength step-by-step phase-out PLS (WSP-PLS) to remove redundant wavelengths in the top 100 EC-PLS models with improved prediction performance. The combination of 19 wavelengths was identi¯ed as the optimal model for SUN. The SEP, R P and RPD in validation were 1.01 mmol L À1 , 0.992 and 7.7, respectively. The prediction e®ect and wavelength complexity were better than those of EC-PLS. Our results showed that NIR spectroscopy combined with the EC-PLS and WSP-PLS methods enabled the high-precision analysis of SUN. WSP-PLS is a secondary optimization method that can further optimize any wavelength ¶ Corresponding authors.

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