| Hyperlipidemia and obesity caused by excessive intake of cholesterols has becomean important factor affecting people’s health. How to lower down the amount ofcholesterols in human beings’ serum has attracted the public attention. In decades, manyresearches proved that fermented food and the lactobacillus in it have good effect inregulating the lipid metabolism and lowering down the amount of cholesterols in humanbeing’s serum. Pickle is a traditional fermented food in China. The researcher screenslactobacillus which can resist bile salts and acid, lower down the amount of cholesterolsfrom the fermented pickles. After physiological and biochemical experiment andmolecular biology identification, the researcher moves on to study lactobacillus’s abilityof resisting bile salts, acid and lowering down cholesterols and its effect on the quality offermented pickles as a starter. In all, this research can provide basic data for studying ordeveloping good starters for fermented pickles and good regulators of blood fatmetabolism probiotics. The main research content and summary are as the follows:(1) The researcher first screened15positive strains from the pickles in market, andthen inoculated them to MRS solid medium. After the second time screening, theresearcher isolated one rod-shaped which can resist bile salts with no spores and signedit as W strain. After gram staining, microscopic examination, physiological andbiochemical experiment and16SrDNA identification, this strain W was identified as alactobacillus plantarum strain.(2) The strain W grows well at0.3percent of bile salt solid medium after24hours,the number of viable bacteria grows up to107cfu/ml. The viability still reaches106cfu/ml at pH1.5after24hours. All the above means that the strain W can survive lowpH value and resist the effects of bile acids in human’s gastrointestinal tract. Theexperiment results of lowering the amount of cholesterol in vitro showed that cholesterollowers about29%in amount in solid medium with no bile salts after24hours, and itlowers33.6%in solid medium with0.2percent of bile salt. Too high, lactic acid bacteriacannot thrive which will then affect their ability of lowering cholesterol, the specificmechanism of lowering cholesterol needs further research.(3) Controlled with naturally fermented pickles, strain W was used as lactic starterto study the effects of different inoculums on fermented pickles. The results showed thatwhen inoculum concentrations were in the range of1.8×104cfu/mL—1.8×105cfu/mL,with the increase of inoculum, the sensory evaluation scores of pickles rised, the pH ofpickle brine dropped more quickly, lowering to pH3.4at the fourth day of thefermentation, while the pH of control test dropped to3.4at the seventh day and the finalpH values of each group were stable at about3.3. The total number of lactic acid bacteriain experimental group and control group peaked respectively at the4d and5d, with concentration above1×1010cfu/mL and1×109.7cfu/mL. Lactic acid bacteria which couldtolerate0.3%of bile salt concentration represented approximately40%of the total in theexperimental group while less than10%of the total in control group. In the experimentalgroup, peak of nitrite content was10mg/kg appearing at the2d and the content was stableat0.5mg/kg at the3d. In the control group, peak of nitrite content was26.4mg/kgappearing at the3d and the content was stable at0.5mg/kg at the6d. These resultsindicated that the addition of strain W could shorten the fermentation time, increase thenumber of lactic acid bacteria especially which could resist bile salt, reduce the contentof nitrite, improve the edible quality of pickles. |
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