Screening And Optimizing Of Antioxidant Lactic Acid Bacteria From Guizhou Kam People Sour Fish And Sour Meat

The sour fish and meat of Guizhou Kam People have characteristics of unique flavor, nutrient-rich, historic features and original ecology production, these traditional sour fish and meat have a long fermention time and can keep for a long time which last from 3 months to decades.However, at present these original ecology femented foods have not yet been developed and utilized efficiently.In this study, the LAB(lactic acid bacteria) have been isolated and identified by combination method of molecular technology and trational physiological and biochemical tests from meterials of the sour meat and sour fish of Guizhou Kam People.The total number of LAB obtained was 23 strains, including 9 pentosaceus, 4Pediococcus, 9 Lactobacillus and a streptococcus.The antioxidant activity of 23 LAB strains was screeninged as indicator of DPPH radical scavenging rate,the 7 LAB strains with DPPH radical scavenging got more than 40% were obtained and the scavenging order from large to small were arranged as follows: SR6(Lactobacillus curvatus strain LAB26),SR10-1(Pediococcus pentosaceus strain LAB42) ﹑ SR13-1(Lactobacillus sakei),SR4-1(Enterococcaceae bacterium Aa MG2),SR9-3(Lactobacillus plantarum WCFS1), SR4-2(Pediococcus pentosaceus strain SWU73571), SR3-1(Pediococcus sp. 22-4), corresponding clearance rate(59.67±6.68)%、(49.48±3.20)%、(48.87±0.88)%、(47.66±2.99)%、(46.32±2.14)%、(45.70±1.70)%、(42.19±0.07)%,in which SR6(Lactobacillus curvatus strain LAB26) had the highest DPPH radical scavenging,higher than the other strains significantly(p〈0.05).The antioxidant activity of these 7 LAB were tested by the rescreening indicators of hydroxyl radical scavenging,reducing power and anti-lipid peroxidation capacity.For hydroxyl radical scavenging,strain with the highest rate was SR4-2(290.00±2.50)%; strain with the lowest rate was SR3-1(146.17±6.33)%. For reducing capacity strain with the highest rate was SR6(47.31±4.62)%; strain with the lowest rate was SR9-3(24.62±5.81)%. For anti-lipid peroxidation strain with the highest rate was SR4-1(68.24±3.06)%; strain with the lowest rate wasSR6(55.00±5.19)%. SR10-1(Pediococcus pentosaceus strain LAB42) was the best performing strain in which the rate of hydroxyl radical scavenging, reducing power and anti-lipid peroxidation reach at(285.67±2.00)%,(44.24±3.46)%,(63.89±0.93)%.And the hydroxyl radical scavenging,reducing power and anti-lipid peroxidation of SR6(Lactobacillus curvatus strain LAB26) were(153.17±5.50)%、(47.31±4.62)%、(55.00±5.19)% respectively. Moreover, DPPH free radical scavenging rate of SR6 was the highest. Above all, strains of SR10-1(Pediococcus pentosaceus strain LAB42)and SR6(Lactobacillus curvatus strain LAB26) were determined as the best strains of antioxidant activity.Effect factors of DPPH radical scavenging of SR6 and SR10-1 were studied by culture conditions and growth conditions. The results showed that carbon, nitrogen and growth factors were the main effect factors. The factos effecting Strains of SR6 were as: carbon> nitrogen> tomato juice> lactose; and strain of SR10-1 effecting factors were as: Lactose> nitrogen> carbon> tomato juice.The growth curve, p H curve, salt and nitrate resistance of SR6 and SR10-1 were determined under optimal conditions by used the medium before and after optimization. Growth curve:0~8h was adjustment, 8h~18h was logarithmic phase,18h~26h tended to stable; p H curve: 0~18h decreased rapidly, 18h~26h stabled or declined slower. Nitrate salt resistance and resistance: when Na Cl concentration is 6%,SR6 and SR10-1 bacteria maintain at 107CFU/m L, when Na NO2 concentration of150mg/kg, SR6 can keep 109CFU/m L, SR6 bacteria maintains at 108CFU/m L. It shows that resistant to salt and nitrate of the two strains were strong.