Bacterial and chemical contaminations of drinking water imperil the health of people.A reactive species injection method is presented for sterilizing drinking water.To produce reactive species,a gas phase surface disc...Bacterial and chemical contaminations of drinking water imperil the health of people.A reactive species injection method is presented for sterilizing drinking water.To produce reactive species,a gas phase surface discharge reactor(SDR)is designed:a spiral stainless steel wire attached on the inside wall of a quartz glass tube is used as the high voltage electrode,and the drinking water is the ground electrode.The performance and mechanisms of the method in inactivating of Escherichia coli(E.coli)are analyzed.Experimental results show that 500 mL E.coli-contaminated drinking water(108CFU/mL)is completely sterilized within 4 min.Based on the scanning electron microscope(SEM)analysis,there were plasma-induced cell structure damages of the E.coli in the sterilized water,and the damage resulted in the leakage of protein,which was proved by chemical analyses.Meanwhile,the heating effect concomitantly generated by discharge plasma does not influence E.coli inactivation,and the contribution of direct ultraviolet(UV)irradiation could be neglected too.The ozone generated by SDR and the hydroxyl radicals(·OH)subsequently generated in drinking water play the decisive roles in E.coli inactivation because these reactive species cause the cell rupture.展开更多
The capacity of five enzymes (P1-P5) to inactivate the trypsin inhibitory activity (TIA) and lectin in raw soybean (RS) and low temperature-extruded soybean (LTES) was examined. P1 is an acid fungal protease with pH o...The capacity of five enzymes (P1-P5) to inactivate the trypsin inhibitory activity (TIA) and lectin in raw soybean (RS) and low temperature-extruded soybean (LTES) was examined. P1 is an acid fungal protease with pH optimum of 5 and P2, P3, P4 and P5 are bacterial proteases with pH optima of 7, 10, 8 and 8 respectively. The results indicated that all enzymes could reduce TIA to a varying degree at their optimum pH. The sequence of effectiveness was P3>P4>P5>P1>P2. The most effective enzyme, P3, reduced TIA to 38% and chymotrypsim inhibitory activity (CIA) to 9% of the original values. After six hours incubation at 50℃, the lectin concentration of LTES and RS was reduced by 50 and 17% respectively by P3, and by 42 and 29% by P4. In the second study, the best enzymes, P3 and P4, were incubated with RS or LTEs at different doses of 0, 0.10, 0.50% or 1.00% (w/w), for periods of 1, 2, 3, 6 or 12 hours. After one hour incubation with P3 at 1.00%, TIA of RS was reduced from 36.60 to 13.30 mg·g -1 . The corresponding values for LTES were 24.50 and 1.90 mg·g -1 . When the incubation was extended to 12 hours, the remaining TIA was 0.90 for LTES and 1.20 mg·g -1 for RS. P4 was not as effective as P3 up to six-hour incubation, but after twelve hours it achieved a similar reduction in activity to that of P3. A kinetic analysis of data showed that the inactivation process of purified soyabean trypsin inhibitors by P3 followed first-order chemical kinetics (Ct=90.90 -0.0408t , r=0.99). The rate of denaturation was -0.0408 per minute. It is concluded that the use of selected enzymes for anti-nutritive factors (ANFs) is an exciting possibility, but still requires further development.展开更多
基金Project supported by Ministry of Science and Technology of China （2008AA06Z308）, National Natural Science Foundation of China （40901150）, Joint Fund of the National Natural Science Foundation of China （U0970166）, Doctoral Program Foundation of Institutions of Higher Education of China （20070141004）, Program for Liaoning Excel- lent Talents in University of China （2009R09）, Fundamental Research Fund for the Central Universities （DUT12RC（3）12）.
文摘Bacterial and chemical contaminations of drinking water imperil the health of people.A reactive species injection method is presented for sterilizing drinking water.To produce reactive species,a gas phase surface discharge reactor(SDR)is designed:a spiral stainless steel wire attached on the inside wall of a quartz glass tube is used as the high voltage electrode,and the drinking water is the ground electrode.The performance and mechanisms of the method in inactivating of Escherichia coli(E.coli)are analyzed.Experimental results show that 500 mL E.coli-contaminated drinking water(108CFU/mL)is completely sterilized within 4 min.Based on the scanning electron microscope(SEM)analysis,there were plasma-induced cell structure damages of the E.coli in the sterilized water,and the damage resulted in the leakage of protein,which was proved by chemical analyses.Meanwhile,the heating effect concomitantly generated by discharge plasma does not influence E.coli inactivation,and the contribution of direct ultraviolet(UV)irradiation could be neglected too.The ozone generated by SDR and the hydroxyl radicals(·OH)subsequently generated in drinking water play the decisive roles in E.coli inactivation because these reactive species cause the cell rupture.
文摘The capacity of five enzymes (P1-P5) to inactivate the trypsin inhibitory activity (TIA) and lectin in raw soybean (RS) and low temperature-extruded soybean (LTES) was examined. P1 is an acid fungal protease with pH optimum of 5 and P2, P3, P4 and P5 are bacterial proteases with pH optima of 7, 10, 8 and 8 respectively. The results indicated that all enzymes could reduce TIA to a varying degree at their optimum pH. The sequence of effectiveness was P3>P4>P5>P1>P2. The most effective enzyme, P3, reduced TIA to 38% and chymotrypsim inhibitory activity (CIA) to 9% of the original values. After six hours incubation at 50℃, the lectin concentration of LTES and RS was reduced by 50 and 17% respectively by P3, and by 42 and 29% by P4. In the second study, the best enzymes, P3 and P4, were incubated with RS or LTEs at different doses of 0, 0.10, 0.50% or 1.00% (w/w), for periods of 1, 2, 3, 6 or 12 hours. After one hour incubation with P3 at 1.00%, TIA of RS was reduced from 36.60 to 13.30 mg·g -1 . The corresponding values for LTES were 24.50 and 1.90 mg·g -1 . When the incubation was extended to 12 hours, the remaining TIA was 0.90 for LTES and 1.20 mg·g -1 for RS. P4 was not as effective as P3 up to six-hour incubation, but after twelve hours it achieved a similar reduction in activity to that of P3. A kinetic analysis of data showed that the inactivation process of purified soyabean trypsin inhibitors by P3 followed first-order chemical kinetics (Ct=90.90 -0.0408t , r=0.99). The rate of denaturation was -0.0408 per minute. It is concluded that the use of selected enzymes for anti-nutritive factors (ANFs) is an exciting possibility, but still requires further development.
