AbstractA lipase-producing bacterium isolated from raw milk was identified as Serratia grimesii based on 16S rRNA sequence analysis. The extracellular lipase was partially purified by ammonium sulfate precipitation and ultrafiltration. Maximal activity was observed at 10°C, the optimum pH was 8.0 and the enzyme was stable at 5–30°C for 1 h. The Km and Vmax values were 1.7 mM and 0.3 mM/min respectively. It was found that the lipase had the highest hydrolytic activity towards sunflower oil and soybean oil. CaCl2 had a stimulatory effect on lipase activity, while EDTA and iodoacetic acid slightly inhibited the lipase activity and the enzyme was strongly inhibited by PMSF. The enzyme was compatible with various non-ionic surfactants as well as sodium cholate and saponin. In addition, the enzyme was relatively stable towards oxidizing agents. This lipase exhibited maximum activity in 35% n-hexane retaining about 2191% activity for 1 h. 相似文献
The esterification of a long-chain fatty acid was conducted using a nylon-immobilized lipase from Candida cylindracea in a nearly anhydrous, nonpolar organic medium, hexane. Butyl laurate was produced from lauric acid and n-butanol at a maximum initial reaction rate of 37 mmol/h. g immobilized enzyme when the substrates were present in equimolar amounts at an initial concentration of 0.5 mol/L. Lower rates were obtained using nonstoichiometric amounts of the substrates. The rate of reaction increased with temperature, reaching a maximum between 35 and 45 degrees C and decreasing sharply at higher temperatures. (c) 1995 John Wiley & Sons, Inc. 相似文献
Candidate plus trees (CPTs) of Pongamia pinnata , a potential biodiesel plant occurring across 10 locations in North Guwahati, were identified based on morphological markers (vegetative and reproductive) using combined analysis over locations. Identified CPTs were then multiplied using seed propagation technique in a nursery bed. The performance of the candidate trees with respect to seed and pod traits, the two most important characters with regard to oil, were evaluated using CROPSTAT software for inferring potential genotypes that can be included in programmes aimed at genetic improvement of the species. Total oil content from the seeds of plus trees was also analysed using solvent extraction procedure at their boiling points. Hexane extraction yielded maximum oil content from seeds (33%) compared with petroleum ether (30%). When the seed to solvent ratio varied, no significant difference was noticed on the total oil yield for an individual tree, although the recovery of solvent and the time taken for oil extraction were significantly reduced at higher ratios of solvent used. 相似文献
It is of interest to analyze the antioxidant, antimicrobial and cytotoxicity activity of n-hexane extract of Cayratia trifolia L. (C. trifolia). The antimicrobial activity of n-hexane extract of C. trifolia was determined using disc diffusion method against six selected pathogenic microorganisms. The cytotoxicity potential of n-hexane plant extract was also studied against A2780 cell lines by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Results, n-hexane extract of C. trifolia possess significant antioxidant activity with significant IC50 values in radical scavenging assays. In antimicrobial studies, the maximum zone of inhibition was found in the range of 19.0 ± 0.1 to 22.0 ± 0.1 mm. In MTT assay, inhibition of cell growth with minimal IC50 values of 46.25±0.42μg/mL against A2780 cell lines was observed. Thus, n-hexane extract of C. trifolia is a possible antioxidant, antimicrobial and cytotoxicity agent. 相似文献
Total Petroleum Hydrocarbons (TPH) is a non-specific parameter defined by EPA Method 418.1. The method is simple, inexpensive and straightforward. Freon 113 is used to extract petroleum from the matrix. The Montreal Protocol precludes the production and importation of Freon 113 into the United States. The search for a cost–effective replacement is underway. US EPA method 1664A Silica Gel Treated N-Hexane Extractable Material (SGT-HEM; Non-Polar Materials) has been considered as a replacement for Method 418.1 by some persons. No comparison data has been provided.
The Tosco Corp. Bayway Refinery has a wastewater discharge permit for Petroleum Hydrocarbons (Oil & Grease) that specifies the use of Method 418.1. The intent of this study was to determine if Method 1664A could replace Method 418.1. Method 418.1 is a direct instrumental measurement of the dried extract. Method 1664A is a gravimetric measurement that requires heating the extract to remove the solvent. Also, a key question to be answered is what carbon range petroleum hydrocarbons does heating the extracts lose? Several evaporation procedures and temperatures were studied.
The study showed that the recovery of petroleum hydrocarbons by method 1664A is temperature dependent and that under the study conditions the method 1664A Silica Gel Treated N-Hexane Extractable Material (SGT-HEM; Non-Polar Materials) can be a replacement for method 418.1. 相似文献
To analyse working conditions and to provide information about the degree to which shoe workers are exposed to n-hexane, the urinary excretion of total 2,5-hexanedione (2,5-HD) was determined in 81 employees in 12 shoe factories. Twenty-five individuals who had experienced no exposure to solvents were used as controls. 2,5-HD was measured in spot urine samples collected from workers at the end of shift. In the urine of shoe workers, the 2,5-HD presented a mean value of 2.33 mg g-1 creatinine, a median of 1.96 mg g-1 creatinine. The mean 2,5-HD concentration in the urine samples from non-exposed subjects was 0.28 mg g-1 creatinine, the median value was 0.18 mg g-1 creatinine. The mean time-weighted average (TWA) concentration of n-hexane in 12 shoe workshops was 126.1 ppm, ranging from 23 to 215 ppm. We found a significant, but low, correlation (r = 0.40; p < 0.001) between TWA intensity of environmental exposure to n-hexane and the concentration of 2,5-HD in urine. The probable effect of toluene on the concentration of 2,5-HD was also discussed in the present study. 相似文献
BACKGROUND: Pre-cleaning and soaking in glutaraldehyde is the necessary procedure to disinfect endoscopes. However, some chemical-solvent-tolerant bacteria may survive after incomplete endoscopic disinfection. The goal of this study was to identify glutaraldehyde resistance-related genes in Helicobacter pylori. MATERIALS AND METHODS: Lambda-Zap phagemid expression library of H. pylori strain NTUH-C1 was selected with 0.1% glutaraldehyde. The minimal inhibitory concentration (MIC) of glutaraldehyde-resistant DNA fragments of H. pylori NTUH-C1 strain were determined. Imp/OstA recombinant protein was expressed, purified, and used to generate anti-Imp/OstA polyclonal antibody. Imp/ostA knockout, deletion, and complementation strains were constructed. The function of Imp/OstA was monitored by organic solvent tolerance assay, antibiotics susceptibility test, and N-phenylnapthylamine assay. RESULTS: Using Imp/ostA polyclonal antibody against cell lysate of wild-type and imp/ostA mutant showed that it is not essential in H. pylori. Organic solvent tolerance assay demonstrated the role of Imp/ostA in n-hexane tolerance. MIC test showed that the mutation of imp/ostA was susceptible to hydrophobic and beta-lactam antibiotics. NPN assay demonstrated that the level of outer membrane permeability was increased by 50% in mutant strain comparing to wild-type strain (p < .001). CONCLUSIONS: We have identified an Imp/OstA protein that was associated with glutaraldehyde resistance in our clinical strain H. pylori NTUH-C1 by screening of lambda-Zap expression library. Disruption of this protein results in altering membrane permeability, sensitivity to organic solvent, and susceptibility to antibiotics. 相似文献
Three major classes of digestive enzymes of squid viscera were characterized following extraction of oil by supercritical
carbon dioxide (SCO2) and organic solvent, n-hexane. Squid viscera were extracted at temperature, 35∼45°C and pressure, 15∼25 MPa for 2.5 h by
SCO2 with a constant flow rate of 22 g/min. Oil extraction yield increased with the increasing of extraction pressure and temperature.
The highest oil extracted residues of squid viscera were used for characterization of digestive enzymes. The activities of
protease, lipase, and amylase were highest in n-hexane treated squid viscera samples and lowest in SCO2 treated samples. The crude extracts of SCO2 and n-hexane treated squid viscera samples showed almost same optimum pH and pH stability for each of the digestive enzymes.
The optimum temperature of protease, lipase, and amylase were found to almost similar in SCO2 and n-hexane treated samples. But the thermal stability for each digestive enzyme in SCO2 treated squid viscera were slightly higher than that of n-hexane treated squid viscera. Studies using SDS-PAGE showed no
significant differences in protein patterns of the crude extracts of untreated and SCO2 and n-hexane treated squid viscera indicating no denaturation of proteins. 相似文献