蛋氨酸羟基类似物体外降解规律研究及对其化学成分潜在风险的检测

Study on Degradation Law of Methionine Hydroxyl Group In Vitro and Detection of Potential Risk of Its Chemical Constituents

研究旨在探究蛋氨酸羟基类似物体外降解规律及对其化学成分潜在风险的检测。采用体外发酵试验,在瘤胃缓冲液中添加奶牛瘤胃液及不同剂量的DL型蛋氨酸(DL-Met)、蛋氨酸羟基异丙酯(HMBi)、羟基蛋氨酸钙盐(HMB-Ca),以无添加为对照组。蛋氨酸产品的添加剂量分别为产品推荐添加量的0、1、2、3、4、5、10倍。培养24 h和48 h后,测定干物质瘤胃降解率,发酵液pH,氨态氮(NH3-N)、微生物蛋白(MCP)、挥发性脂肪酸(VFA)浓度,并对化学杂质(甲硫醇、丙酮、异丙醇、丙烯以及氰化物)浓度进行检测。结果表明:①除HMBi 48 h时1倍剂量的干物质降解率显著低于同一发酵时间段的2、3、4、10倍添加剂量外(P<0.05),三种蛋氨酸产品发酵同一时间不同剂量间的降解率均无显著差异(P>0.05)。②DL-Met在发酵24 h时10倍添加剂量的NH3-N浓度显著低于同一发酵时间段0~4倍添加量,48 h的10倍添加剂量的NH3-N浓度显著低于同一发酵时间段0~2倍添加量;HMBi发酵48 h时10倍添加剂量的NH3-N浓度显著低于同一发酵时间段0、1、2、4倍添加剂量(P<0.05)。③三种培养液发酵48 h不同剂量的MCP浓度存在显著差异(P<0.05),而24 h时差异不显著(P>0.05)。④除DL-Met影响pH外(P<0.05),其他产品同一时间不同剂量间差异不显著;在VFA方面,HMBi发酵液在发酵48 h时0倍添加剂量丁酸比例显著低于1、3、10倍添加剂量(P<0.05)。⑤三种产品培养液中均含有甲硫醇、丙酮和异丙醇杂质,但杂质浓度没有随产品剂量增加而升高,且未检测出含有丙烯和氰化物。研究认为,蛋氨酸羟基类似物对奶牛体外发酵没有显著影响,但在其培养液中会出现产品生产过程中的部分化学物质。

The purpose of this study was to explore the external degradation rules of the methionine hy⁃droxyl-like group and the detection of the poten⁃tial risks of its chemical composition.By in vitro fermentation test,cow rumen fluid and different doses of dl type methionine(DL-Met),isopropyl methionine(HMBi),hydroxymethionine calcium salt(HMB-Ca)were added to the rumen buffer,and no addition was used as the control group.The additive amount of methionine products were 0,1,2,3,4,5 and 10 times of the recommended additions.after 24 and 48 h of incubation,the concentrations of dry matter ruminal degradation,broth ph and ammonia nitrogen(NH3-N),microbial protein(MCP),volatile fatty acids(VFA)were measured,and the concentrations of chemical impurities(methylthiol,acetone,isopropanol,propylene,and cyanide)were tested.the results showed that:①Except that the degradation rate of hmbi 48 h was significantly lower than 2,3,4 and 10 times the additives in the same fermentation time period(P<0.05),the degrada⁃tion rate between different doses at the same time(P>0.05).②The NH3-N concentration of DL-Met at 10 times the added dose for 24 h of fermentation was significantly lower than that at 0 to 4 times the add⁃ed amount during the same fermentation period,and the nh3-n concentration at 10 times the added dose for 48 h was significantly lower than that at 0 to 2 times the added amount during the same fermentation period;the concentration of NH3-N at 10 times the added dose for 48 h of hmbi fermentation was signifi⁃cantly lower than that at 0,1,2,and 4 times the added dose during the same fermentation period(P<0.05).③The concentration of mcp at different doses of the three products at 48 h(P<0.05),but not dif⁃ferent between dose groups at 24 h(P>0.05).④Except for the effect of DL-Met on ph(P<0.05),there was no significant difference between different doses of other products at the same time;in terms of vfa,the proportion of butyric acid at 0 times the added dose in hmbi fermentation broth was significantly low⁃er than that at 1,3,and 10 times the added dose after 48 h of fermentation(P<0.05).⑤The culture me⁃dia of the three products contained methylthiol,acetone and isopropyl alcohol impurities,but the impuri⁃ty concentration did not increase with the increase of the product dose,and no propylene and cyanide were detected.It is believed that the methionine hydroxyl analogues have no significant effect on the in vitro fermentation of dairy cows,but some chemicals in the product production process will appear in their culture medium.