饲用油菜中优势乳酸菌的分离鉴定及其对青贮发酵品质和有氧稳定性的影响

Isolation and Identification of Dominant Lactic Acid Bacteria from Brassica napus and Their Effects on Fermentation Quality and Aerobic Stability of Silage

本研究旨在筛选出饲用油菜(Brassica napus)青贮中天然附着的优势乳酸菌,明确其对饲用油菜青贮发酵品质和有氧稳定性的影响,为饲用油菜资源高效饲料化利用提供指导。首先利用分子生物学法(16S rDNA测序)对分离出的乳酸菌进行鉴定,鉴定出的乳酸菌菌株进行产酸和生长特性分析。进一步将筛选的优势乳酸菌接种至饲用油菜中青贮,采用裹包青贮法,试验设置4个处理:对照(CK)处理不接种菌株;布氏乳杆菌(LB)处理接种布氏乳杆菌,接种量为2×10^(8) CFU/g;屎肠球菌(EF)处理接种屎肠球菌,接种量为2×10^(8) CFU/g;布氏乳杆菌+屎肠球菌(LBEF)处理接种布氏乳杆菌+屎肠球菌(1∶1),接种量均为1×10^(8) CFU/g。结果表明:1)试验共计分离出26株乳酸菌,鉴定后得出25株为布氏乳杆菌,1株为屎肠球菌,其中2株表现出最强的产酸和生长特性。2)发酵60 d时,LBEF处理的中性洗涤纤维和丙酸含量显著低于CK和EF处理(P<0.05);EF和LBEF处理的酸性洗涤纤维含量显著低于CK和LB处理(P<0.05),乳酸含量显著高于CK和LB处理(P<0.05);LB、EF和LBEF处理的pH、氨态氮含量、霉菌数量均显著低于CK处理(P<0.05)。3)开包5 d时,EF和LBEF处理的乳酸含量和乳酸菌数量显著高于CK和LB处理(P<0.05),LBEF处理的丙酸含量显著低于其余处理(P<0.05),LB和LBEF处理的氨态氮含量显著低于其余处理(P<0.05),LBEF和LB处理的酵母菌和霉菌数量显著低于CK和EF处理(P<0.05)。由此可见,在饲用油菜青贮中联合接种布氏乳杆菌和屎肠球菌,可利用底物较少的营养物质产生乳酸,以降低发酵体系pH,抑制蛋白质腐败和霉菌生长,提高饲用油菜有氧稳定。

The aim of this study was to screen the naturally dominant lactic acid bacteria in Brassica napus silage,and determine their effects on fermentation quality and aerobic stability of forage rape silage,so as to provide guidance for efficient feed utilization of Brassica napus resources.Firstly,the isolated lactic acid bacteria were identified by molecular biology method(16S rDNA sequencing),and the identified lactic acid bacteria strains were analyzed for acid production and growth characteristics.Further,the selected dominant lactic acid bacteria were inoculated into Brassica napus for silage,and the wrapped silage method was adopted.Four treatments were set up in the experiment:the control(CK)treatment was inoculated no bacterial strains;the Lactobacillus buchneri(LB)treatment was inoculated the Lactobacillus buchneri,and the inoculation amount was 2×10^(8) CFU/g;the Enterococcus faecium(EF)treatment was inoculated the Enterococcus faecium,and the inoculation amount was 2×10^(8) CFU/g;the Lactobacillus buchneri+Enterococcus faecium(LBEF)treatment was inoculated the Lactobacillus buchneri+Enterococcus faecium,and the inoculation amount was all 1×10^(8) CFU/g.The results showed as follows:1)26 lactic acid bacteria were isolated in this experiment,of which 25 strains were identified as Lactobacillus buchneri and 1 strain was Enterococcus faecium.Two of them showed the strongest acid production and growth characteristics.2)On 60 days of fermentation,the contents of neutral detergent fiber and propionic acid in LBEF treatment were significantly lower than those in CK and EF treatments(P<0.05);the content of acid detergent fiber in EF and LBEF treatments was significantly lower than that in CK treatment(P<0.05),and the content of lactic acid was significantly higher than that of CK and LB treatments(P<0.05);the pH,ammonia nitrogen content and mold number in LB,EF and LBEF treatments were significantly lower than those in CK treatment(P<0.05).3)On 5 days of unpacking,the lactic acid content and lactic acid bacteria number in EF and LBEF treatments were significantly higher than those in CK and LB treatments(P<0.05),the content of propionic acid in LBEF treatment was significantly lower than that in other treatments(P<0.05),the content of ammonia nitrogen in LB and LBEF treatments was significantly lower than that in other treatments(P<0.05),the numbers of yeast and mold in LBEF and LB treatments were significantly lower than those in CK and EF treatments(P<0.05).In conclusion,the co-inoculation of Lactobacillus buchneri and Enterococcus faecium in Brassica napus silage can use nutrients with less substrate to produce lactic acid,reduce the pH of fermentation system,inhibit protein spoilage and mold growth,and improve the aerobic stability of Brassica napus.