The Development Of Thermal Stable Lactobacillus Feed Additives

With the growing awareness of food safety,the application of microecologics,which are nature,safe and residue free,for replacing antibiotics as feed additives has been widely recognized by feed industry.Among the 16 microorganisms approved for utilization in microecologics,L.acidopholus is the most favorite one,because it possesses gut microbiota modulation,immunity enhancement and production performance improvement effect.In addition,for L.acidopholus has the function of producing acid,it can be used to replace the acidifier for weaned piglets.However,the poor thermal stability of L.acidopholus limits its application in feed industry.In the present study,a mutative L.acidophilus strain was developed by ultraviolet mutation and high-temperature acclimation.The temperature tolerance,growth characteristics,acidogenicity and digestion resistant capability of this strain were also evaluated in this study.Then the optimal fermentation and spray dehydration conditions of mutant strain were studied.At last,the application effect on weaned piglets was studied.The main contents and results were as follows:The original L.acidophilus strain FZU-LA 1301 was treated with UV mutation and high temperature acclimation.After a series of UV mutation and high temperature acclimation treatment,a thermo tolerant strain FZU-LA1301X was developed.The results indicated that,after mutation and acclimation,temperature tolerance was increased from 37 ℃ to 45 ℃.The stationary phase of the strain appeared at 15 h,which was shorten from 24 h.In anaerobic environment,the viable number reached 8.24 log CFU/mL during stationary phase.After mutation and acclimation,there was no significant change in pH value of the fermentation broth,which were both around 4.0.The mutant stain had a certain tolerance ability of pepsin,trypsin and bile salts.Secondly,the fermentation condition for the mutative starin were optimized.Based on MRS medium,the optimized culture medium was as follows:1.0%sucrose;0.4%peptonand with 3%cucumber juice as growth promoting factors.The optimized fermentation conditions were as follows:initial pH 6.2:inoculation amount 2%;fermentation time 15h.The final cell density was 8.64 log CFU/mL.Then,the spray dehydration conditions for fermentation broth were optimized too.Gum acacia,maltodextrin,soluble starch power,β-Cyclodextrin and gelatin as the wall material to protect the strain during spray dehydration process were compared.The results indicated that the combination of gum acacia and maltodextrin with the ratio of 1:7 had the best protection effect for the strain.The optimal conditions of spray dehydration of L.acidopholus were developed by using orthogonal experiment.The optimal entrance temperature was 160℃,flow rate was 400mL/h,wall-material concentration was 20%,and wall-material ratio was 1:9.The viable counts of microencapsulated L.acidopholus reached 8.69 log CFU/g and the microencapsulation efficiency was 72.18%.After stored at room temperature for 30 days,the viable counts of microencapsulated L.acidopholus maintained over 106cfu/g.In the end,an animal test was conducted to examine the application effect of the products.With weaning piglets as the subjects,the microencapsulated L.acidopholus were feed to the experimental animals for 4 weeks.The results showed that,compared with the blank control,the daily gain and daily feed intake of piglets feed with microecologics increased 7.35%and 2.54%,respectively(P<0.05),moreover the diarrhea rate and mortality rate decreased 57.55%and 40.03%,respectively.In addition,increase 14.23%of Lactic acid bacterium and decrease 11.25%of Escherichia Coli was also found in piglets feed with microecologics.