Selection of nitrite and bioamine-degrading bacteria and its improvement of fish sausage quality

Abstract: In order to improve the quality and food safety of Chinese fermented fish sausages, the activities of nitrite and biogenic amines degradation and related genes distribution in 19 Lactobacillus plantarum strains from different sources were investigated. The results showed that all strains had the ability of nitrite degradation with the reducing rate of 36%-95%. Among them, L. plantarum CP3 and MP1 (isolated from cupei and milk product respectively) had the strongest nitrite reducing ability, and the degrading rate could reach above 95% after 72 h. PCR (polymerase chain reaction) test suggested that all strains contained HP (hypothetical protein) gene. Detection rates of the other 2 nitrite degradation related genes GR (glutathione reductase) and ORD (oxidoreductase) were 47.36% and 42.10% respectively. There are few reports on genes of nitrate reductase in lactic acid bacteria. In future, the 3 genes encoding proteins sequence, enzyme activities and gene expression regulation should be studied in depth. Additionally, Suf I (multicopper oxidases) gene could be detected in all 19 strains. However, the biogenic amine degrading rate was so different, from 20% to 77%. There were 6 strains showing the degrading activity to all 8 tested biogenic amines. Ten strains (tryptamine degradation), 2 strains (putrescine degradation), 7 strains (tyramine degradation) and 3 strains (tyramine degradation, arginine degradation and spermidine degradation respectively) exhibited degradation rate of more than 50%. Also, we proved that the excellent target strain (L. plantarum CP3) did not contain potential harmful biogenic amines producing genes such as hdc (histidine decarboxylase gene), tdc (tyrosine decarboxylase gene) and odc (ornithine decarboxylase gene). Further, the effects of L. plantarum CP3 on nitrosamines, biogenic amines, microorganism and physico-chemical index of fish sausages were researched. The results showed that L. plantarum CP3 had a high inhibitory effect on all 4 N-nitrosamines: N-nitrosodiethylamine (NDEA), N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMOR) and N-nitrosomethylamine (NMEA). Moreover, this ability could be synergistically enhanced when inoculated with L.saki M4 (another excellent strain for sausage fermentation in our previous study, which could produce bacteriocin). After 48 h fermentation, the putrescine, cadaverine and tyramine content were reduced by 76.83%, 93.33% and 88% respectively in the test group. Moreover, the results clearly demonstrated that due to the L. plantarum CP3 and L.saki M4 inoculation, lactic acid bacteria rapidly became dominant ?ora and the growth of food-borne pathogens, such as Enterobacteria spp. and Pseudomonas spp., was completely inhibited during sausages fermentation. Additionally, the pH values, thiobarbituric acid (TBA) and total volatile basic nitrogen (TVB-N) content were sharply reduced in inoculated sausages. In conclusion, L. plantarum CP3 can be considered as excellent candidate for microbial culture starters in fermented sausage production to inhibit nitrosoamines and biogenic amines accumulation and improve the product quality and safety.