High Cell Density Culture And Microencapsulation Of Lactobacillus Paracasei

Lactic acid bacteria play an important role in maintaining human health, such as improving intestine functions, enhancing the immune system and decreasing serum cholesterol, which are widely used in food industry. The high-density culturing and high activity maintaining constitute the decisive factor for effective application of lactic acid bacteria. In this paper, the viable count of Lactobacillus paracasei were increased gradually through culture condition optimization, lactic acid-resistance domestication and enrichment medium optimization. And on this basis, the effects of microencapsulation on the efficiency of Lactobacillus paracasei preparation were studied. Four microcapsule preparation methods were compared and the wall material, protective agent and processing condition of microcapsules were optimized. The main research contents and results were as follows:The optimal culturing conditions of Lactobacillus paracasei were: initial pH6.5, inoculation1.5%and temperture37℃. Lactobacillus paracasei were domesticated by gradually lowering the pH of liquid medium by lactic acid and domesticated Lactobacillus paracasei could growth well in medium of pH5.0and the total viable count in normal medium cultured for21h was1.19×109CFU/mL. The culture medium of domesticated Lactobacillus paracasei were optimized by means of single factor method, Plackett-Burman design and response surface methodology and obtained the optimal enrichment medium was composed of3%yeast extract,2.48%lactose,0.8%NH4H2PO4,0.5% isomaltooligosacharide and11.97%potato juice, the final viable counts of Lactobacillus paracasei was increased nearly four times under the optimal condition.The optimization processing conditions of extusion method were soy protein isolate (SPI)4%, isomaltooligosacharide7%, sorbitol5%, sodium alginate2%, calcium chloride2%, the encapsualtion yeild was83.23%, the survial rate of Lactobacillus paracasei was14.17%after freeze drying and reached63.45%after28days stored under4℃. Although extrusion method has a higher efficiency for Lactobacillus paracasei microencapsulation, it only can be used as laboratory research for its time-consuming and laborious process. Protein gel microcapsules preparation process found that the freeze drying survival rate of Lactobacillus paracasei was only3.02%, but the storage survival rate of Lactobacillus paracasei was22.54%after stored28days under4℃with SPI concentration of10%, sodium alginate concentration of0.5%and CaCl2concentration of1-1.5%, and the encapsualtion yield of it was31.07%.5%microporous starch adding, absorbing temperature of20℃, shaking for40min were the optimum adsorption conditions of porous starch for Lactobacillus paracasei, the encapsualtion yield of microcapsules was20.87%and the survival rate of Lactobacillus paracasei was only2.10%after freeze drying. Protein gel method and porous starch absorption method applied to Lactobacillus paracasei microcapsules preparation has the features of convenient and economical, but only by combining with other technologies can be used effective since its poor encapsulation effect. The yield of Lactobacillus paracasei microcapsules by spray drying was75.21%, and the survival rate of Lactobacillus paracasei was reached87.7%under the best conditions of inlet and outlet temperature were150℃and65℃,8%SPI and4% gelatin-gum acacia as wall materials,5%mannitol as protective agent, and the storage survival rate of Lactobacillus paracasei was48.12%after stored28days under4℃. The preparation techniques of Lactobacillus paracasei microcapsules by spray drying is simple, convenient for collecting and suitable for the industrialized application, and with a good survival rate of Lactobacillus paracasei.