Study On Quantification And Inactivation Of Lectins In Feeds

This study was carried out to study the quantification and inactivation of lectins in feeds. A rapid quantification was established according to the relationsheep between the heammagglutinin activities and its content(Expt. 1 and 2). Toxicity of phaseolus vulgaris lectin (PHA) was examined using mice as experimental animals in Expt.3. The methods of inactivation were recognised after studying the effects of physico-chenmical treatments on its activities(Expt.4).In Expt.l, method of purification of lectins. Soybean agglutinin (SBA), a important kind of lectins, was extracted and purified through affinity chromatography, with GalNAC as adsorbent and Epoxy-Sephrose as Vector. Separation was performed on a GalNAC- Epoxy-Sephrose column (2.5x20cm), and the mobile phase consisted of phosphatic buffer- sodium(PBS )(pH 7.2). At first, the extrat of the defated soybean powder was adsorbed to the column. After eluting to baseline (OD280nm<0.01), then the tubes whose OD280nm>0.2 was collected, dialysed and freeze-dried, and then purified SBA was obtained.Method of an qutification of lectin was studied in Expt.2. A new method of quantification of the lectin in feed, Hemagglutination, was proposed based on the relationship between its hemagglutinating activity and concentration. Investigation was made on effects of different factors on determination, including the particles size of sample crushed, defatting method, extracting method. There was a close correlation between the hemagglutinating activity and the concentration of lectins (R2=0.99). In order to obtain good results, samples shoud be crushed to 40 mesh, both ratios (W/V) of sample to aetheris and sample to saline solution were 1:8, each lasting for 8 hours. Under the above conditions, the recovery(%) of lectin was between 88-102.The Expt.3 was aimed to study the toxicity of PHA to Kunming mouse. Mice weighing 18-24g were chosed and divdied into three groups at random. Different doses of PHA were inoculated into stomach of mice under appropriate condition. The doses of PHA were 25~250, 500~1500 and 5 000~15 000 g/kg BW, in three separate trials, respectively. All the tested mice were alive seven days later, indicating that the PHA has no acute toxicity to mice.In Expt.4, four kinds of inactivation methods, dry-heat, moist heat, acid-alkali and metallic cations were employed to investigate their effects on the activities of SB A. Dry heat treatment below 120C did not obviously decrease the activities of SB A, while moist heat treatment (95C for 30min, 100C for 20min, 105C for 10min) completely inactivated the SBA. The activities of SBA significantly decreased when soybean protein was extracted under pH1.0-4.5 or pH9~13. Quadrivalent and trivalent metallic cations markedly inhibited activities of SBA.In summary, lectins can be successfully purified by affinity chromatography. Heamagglutination can be used to quantify the lectins in feeds conveniently. The PHA has no Acute Toxicity to mouse. Proper physico-chemical treatments can efficiently inactive the lectins in feeds.