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Study on High-Density Cultivation and Activity Protection of Liquid-Core Encapsulated Lactobacillus Sake LS10

Author: YuanZuo
Tutor: DongMingSheng
School: Nanjing Agricultural College
Course: Of Food Science
Keywords: liquid-core capsule Lactobacillus sake high-density cultivation deep-frozen protectants high-activity concentrated starter
CLC: TS251
Type: Master's thesis
Year: 2008
Downloads: 51
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Abstract

Fermented meat in our country has a long history encompassing more than thousand years,but the use of microbial starter in meat processing has started only recently.People have now comprehended the role of lactic acid bacteria and other microorganism in overall quality and preservation of fermented meat.In European and American countries,starter is applied more and more extensively in meat industry.Our country is the major producer and consumer of fermented meat and there are a range of different fermented meats available all over the country.The demand for supreme quality and diversified meat products is sharply increasing with the improvement in people’s living standards,while traditional processing technology no longer meet the requirement of modernized fermented meat. Therefore,in order to promote the development of the fermented meat industry,it is highly imperative to develop safty and high-activity meat starter to give a boost to meat processing industry.Starting with the crux technology of preparing high-activity concentrated lactic acid bacteria as meat starter.The present research used liquid-core capsule immobilized technology on Lactobacillus sake LS10 which was isolated from fermented meat.The concentration of L.sake LS10 was studied using the single factor experiments,response surface methodology and orthogonal designs to optimize the enrichment media and culture conditions.Screening the optimal deep-frozen protective for encapsulated L.sake LS10 was done to improve the cell viability.The study provided a theoretical basis for preparing new immobilized lactic acid bacteria as meat starter.The main results were as follows:1.Preparation of microencapsulated L.sake LS 10Lactobacillus sake LS10 was immobilized in calcium alginate capsules by using liquid-core method and conventional embedding method,respectively.The capsulated cell density of liquid-core microcapsule was obviously higher than that of gel bead under the same culture condition.According to the test purpose,the liquid-core method was chosen.2.Study on high-density cultivation of microencapsulated L.sake LS10Based on whey culture medium,and supplemented with carbon source,nitrogen source,growth factors,pH-buffer,the optimum culture medium was determined by single factor experiments and response surface methodology.It was found that the strain LS10 required the following ingredients for the optimal growth(L^-1):whey powder 60g,glucose 18.87g,peptone 21.98g,tomato juice 98.62mL,CaCO₃ 4.39g,MgSO₄ 0.28g and MnSO₄ 0.18g.The results of orthogonal designs showed that the optimal culturing conditions were temperature 37℃,pH 7.0,culture time 20h,inoculum 1%.At the optimized condition,the cell concentration in the liquid-core capsules was increased to 10.59 log（cfu/g）.3.Study on activity protection of microencapsulated deep-freezing starterCell viability of Lactobacillus sake LS10 was compared under different freezing temperature（-20℃and -70℃） and different thawing temperature（4℃,22℃and 42℃）. The optimum freezing temperature was found to be -70℃while the optimum thawing temperature 42℃.Plackett-Burman design was used to evaluate the deep-frozen protective effect of sucrose,lactose,glucose,fructose,maltodextrin,glycerol,mannitol,sorbitol,gelatin,skim milk,L-cysteine hydrochloride,arginine,ascorbic acid and sodium glutamate on encapsulated L.sake LS10.Results showed that sucrose,glycerol,sodium glutamate and skim milk were the effective deep-frozen protectants for L.sake LS10.Then the central composite design and response surface analysis were used to determine the optimal levels of these media.The results showed that the optimal protective medium for enhancing the viability of deep-frozen L.sake LS10 was sucrose 45.75g/L,glycerol 63.95 mL/L,sodium glutamate 64.70g/L,and skim milk 92.93 g/L,which allowed the cell viability of L.sake LS10 up to 92.54%after deep-freezing.On the basis of preparation of deep-frozen concentrated meat starter,the change of bacterium count under different storage conditions（-20℃and -70℃） was studied.The results showed that frozen storage at -70℃contributed more to L.sake LS10 protection than that at -20℃,the cell viability was 63.59%six months later.

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