Preparation And Application Performance Lactobacillus Acidophilus As The Probiotics

Southern Catfish is our national tradition of famous freshwater fish, which is the traditional rare and economy freshwater fish of Sichuan province. However, the low immunity and higher incidence could induce the large number of deaths in eggs hatch, larval rearing and juvenile stages. In recent years, probiotics as green-feed additives gradually replaced antibiotics, but rare in southern catfish feeding probiotics. Lactobacillus acidophilus is one of the beneficial bacteria which perched on the animal intestinal bacteria, but it is susceptible to the influence of light, oxygen, acid in the course. Microencapsulation could improve the living cell number and stability of probiotics.First, the effects of different addition of porous starch as main wall material on the probiotics embedding rate and biological characters was investigated. When the wall material was added mass fraction of 10% of the porous starch, the highest embedding rate of living bacteria reached 61.2%, and the shape of probiotics is nearly spherical. Moreover, the number of micropores on the surface is appropriate. After exposed 3 hours in artificial gastric juice of pH1.5, the number of living bacteria decreased from 6.54 log to 2.63 log, and after exposing 12 hours in 2% bile salt solution, viable counts only decreased 2 log cycle. After heating of 20 min at the 50°C, 60°C, 70°C conditions, viable counts were decreased by 1.01 log, 2.08 log and 3.10 log, respectively. At the same time, releasing test was conducted in the simulated colonic pH environmental of 37°C and the released viable number reached 6.09 log after 1.5h.Second, effects of different materials on the biological properties of Lactobacillus acidophilus as the probiotics was investigated. It was found that the shape of probiotics composited by 10% porous starch, 3% glycerol and 2% mannitol was irregular spherical without a lot of lumps and debris. After incubating for 20 min at 50°C, 60°C, 70°Cconditions, the number of viable cells were maintained 8.16, 7.17, 6.42 cycles. After storing at 4°C for 12 weeks, the number of probiotic cells with the composite wall material reduced from 9.08 log to 7.86. However, the number of free cells reduced to 4.12 log. Moreover, the released cell numbers were 6.46, 8.34 log after incubating for 1h and 2h in the simulated colonic pH, respectively.Third, the best composite of wall material and preparation condition were optimized through orthogonal test. The best composite of wall material and preparation condition were determined as follows: the bacterium suspension 50 mL, the assist wall materials including glucose 5.0g, glycerol 4.0g and mannite 3.0g, the porous starch dosage 5.0 g,shaking time 40 min, embedded pH 6.0 and embedded temperature 20°C. Under these conditions, the embedding rate of sample was 59.5% and the size of micro ecological was uniform. After digesting for 60 min in artificial gastric juice, the number of living bacteria decreased 3 log. After digesting for 30 min in the artificial intestinal, the probiotics could be completely dissolved. TGA analysis and experimental results showed that the probiotics had good storage properties., Microencapsulation containing Lactobacillus acidophilus showed the better property after stored at 4°C and 25°C for 6 weeks. At the same time, the temperature of 4°C was more conducive to the preservation of microencapsulation containing Lactobacillus acidophilu.Finally, catfish weight has increased significantly feed with Lactobacillus acidophilus probiotics prepared with the composite wall materials and the best process condition. Moreover, while the texture of catfish was also significant differences. The hardness, chewiness of the probiotic group had a significant increase compared to the control group, The decline of adhesive was found. However, the difference of elasticity is not obseved. In addition, the moisture and ash content of probiotic group decreased compared with the control group, but the fat and protein content increased by varying degrees. By the correlation analysis between texture index and growth performance, the full description of Lactobacillus acidophilus probiotic significantly promoted the growth of catfish.