ABSTRACT
The overuse of organophosphorus pesticides on cotton production is a big concern in China today. Therefore, developing methods for the rapid screening and confirming of pesticide residues in textiles has become a top public health security priority. Here, a method was established for the rapid screening and quantifying of 11 kinds of organophosphorus pesticides (ethoprophos, coumaphos, profenofos, diazinon, ethion, parathion, phosalone, quinalphos, dicrotophos, azinphos methyl, and tribuphos) in textiles by high-performance liquid chromatography high-resolution mass spectrometry (HPLC-HRMS). Rapid screening and quantifying could be completed by using software of Peakview and MultiQuant. Samples were extracted by the method of modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) and analyzed in the positive mode with MS detection. The results showed that the limits of detection were between 0.1 and 5.0 ng g-1, with correlation coefficients above 0.9990. The recoveries were in the range of 70.3 - 109.8%, with relative standard deviations from 5.1 to 16.4%. This method is accurate and simple, which can be used in the rapid screening and quantitative analysis of 11 kinds of organophosphorus pesticides in textiles.
ABSTRACT
It is always a challenge to determine the total cellulase activity efficiently without reducing accuracy. The most common total cellulase activity assay is the filter paper assay (FPA) established by the International Union of Pure and Applied Chemistry (IUPAC). A new procedure to measure the FPA with microplate-based assay was studied in this work, which followed the main idea of IUPAC to dilute cellulase preparation to get fixed glucose release. FPAs of six cellulase preparations were determined with the microplate-based assay. It is shown that FPAs of cellulase Youtell, RCconc, R-10, Lerkam, Yishui and Sinopharm were 67.9, 46.0, 46.1, 27.4, 7.6 and 8.0 IU/ml respectively. There was no significant difference at the 95% confidence level between the FPA determined with IUPAC and the microplate-based assay. It could be concluded that the FPA could be determined by the microplate-based assay with the same accuracy and much more efficiency compared with that by IUPAC.
ABSTRACT
Hydrolysis of cellulose to glucose is the critical step for transferring the lignocellulose to the industrial chemicals. For improving the conversion rate of cellulose of corn stover to glucose, the cocktail of celllulase with other auxiliary enzymes and chemicals was studied in this work. Single factor tests and Response Surface Methodology (RSM) were applied to optimize the enzyme mixture, targeting maximum glucose release from corn stover. The increasing rate of glucan-to-glucose conversion got the higher levels while the cellulase was added 1.7µl tween-80/g cellulose, 300µg ß-glucosidase/g cellulose, 400µg pectinase/g cellulose and 0.75mg/ml sodium thiosulphate separately in single factor tests. To improve the glucan conversion, the ß-glucosidase, pectinase and sodium thiosulphate were selected for next step optimization with RSM. It is showed that the maximum increasing yield was 45.8% at 377µg/g cellulose Novozyme 188, 171µg/g cellulose pectinase and 1mg/ml sodium thiosulphate.
Subject(s)
Cellulase/metabolism , Glucose/metabolism , Lignin/metabolism , Polygalacturonase/metabolism , Zea mays/metabolism , beta-Glucosidase/metabolism , Hydrolysis , Kinetics , Multienzyme Complexes , Polysorbates/chemistry , Surface-Active Agents/chemistry , Thiosulfates/chemistryABSTRACT
OBJECTIVES: To optimize nisin production in Lactococcus lactis by using different aeration and fermentation strategies. RESULTS: The nisin titer and specific nisin production rate reached maximum values of 11,900 IU/ml and 4110 IU/g/h, respectively, in aerobic batch fermentation with glucose as C source. These values were higher than in anaerobic batch fermentation (10,700 IU/ml and 3260 IU/g/h, respectively). The maximum specific nisin production rates appeared earlier in aerobic batch fermentation, which suggests that nisin production is stimulated by aeration. Different fermentation strategies were compared: maximum nisin production (15,400 IU/ml) was achieved with fed-batch fermentation with a variable rate of feeding under aerobic conditions. CONCLUSION: Nisin production can be stimulated by aeration, which goes against the typical conditions involving strict anaerobiosis.
