降胆固醇干酪乳杆菌WB生长培养基的筛选

降胆固醇干酪乳杆菌WB在不同种类选择性培养基上生长培养后,比较活菌菌落数、菌落及溶钙圈大小。结果显示:MRS培养基最适合降胆固醇乳酸菌WB的培养,活菌数最多、菌落及溶钙圈最大。厌氧培养后效果更佳。     

分离传统酸马奶中乳酸菌的最适培养基的筛选

以采集于新疆地区的10份酸马奶样品为研究对象,通过对比5种(MRS培养基、MRS合成培养基、M17培养基、MRS+X-gal培养基和MRS+蘑菇汁+番茄汁培养基)不同的培养基上进行乳酸菌的活菌计数,且分析分离株统计结果筛选出最适于乳酸菌的生长、分离的培养基。实验表明,MRS合成培养基更加适合乳酸菌的生长,其活菌数最高,便于乳酸菌计数。     

发酵乳杆菌CECT5716计数方法比较

针对中外乳酸菌菌落数检测标准的差异,从固体菌粉的溶解情况以及培养基成分入手,通过比对菌落生长情况找出问题所在并提出可行性改进意见。结果表明,两种标准中所用混匀方式对菌落计数无影响;冷冻保藏的固体菌粉在后续实验操作前37℃下复溶45 min能够提高其活力,是造成中外差异的因素之一;复溶时用1%缓冲蛋白胨水进行溶解对缩短中外标准菌落数检测结果有积极作用;在培养基中加入适量营养物质能够显著提升菌落生长数量。     

蛋白酶水解脱脂乳培养基的优化

为减少进口发酵剂的使用,降低国内乳制品的生产成本,国内需要自主研发发酵剂,水解脱脂乳培养基的优化是发酵剂制备过程中的一个重要环节。为制备有利于乳酸菌生长的水解脱脂乳培养基,本研究首先以发酵乳杆菌V9为试验菌种,筛选出水解脱脂乳最适的蛋白酶,再通过单因素与正交实验对制备脱脂乳水解液的温度、时间、pH值、加酶量进行优化。结果表明,最适水解条件为:在p H为8.5的12%脱脂乳中按25 U/mL接入碱性蛋白酶,55℃水解1 h,以此水解脱脂乳为培养基培养乳酸菌活菌数达到2.5×109CFU/mL,较脱脂乳培养基中的活菌数提高了1.74倍。利用此优化培养基培养鼠李糖乳杆菌grx19和植物乳杆菌S7,得到的活菌数分别较脱脂乳培养基提高了1.50和1.62倍。     

与酵母菌具有共生作用乳酸菌LC5培养基的优化

用对酵母菌(YE4)有促进作用的乳酸菌(LC5)为研究对象,以OD值和活菌数为测定指标筛选合适的培养基。通过对5种乳酸菌常用培养基的筛选,确定M17培养基中LC5生长良好。以M17培养基作为基础培养基,进一步利用单因素试验和正交试验的设计方法对其进行优化,得出改良M17培养基的最佳成分为:大豆蛋白胨为0.6%,胰蛋白胨为0.6%,牛肉膏为0.4%,酵母浸提粉为0.5%,K2HPO4为0.7%,盐液A为0.4%,甘油为0.8%,乳糖为0.6%。优化后的培养基乳酸菌LC5的活菌数可达到1.89×109cfu/mL,是基础培养基的5.9倍,OD值是M17基础培养基的1.22倍。     

自制蛋白胨在乳酸菌培养中的应用

为了提高乳酸菌培养过程中的活菌总数,利用自制蛋白胨取代对照培养基中的氮源对乳酸菌进行培养。采用微生物菌液浊度测定法和微生物活菌计数法对培养结果进行测定。结果表明,用自制蛋白胨作为氮源取代对照培养基中的部分氮源培养植物乳杆菌、干酪乳杆菌、嗜热链球菌、双歧杆菌时的菌液浊度和活菌总数均高于对照培养基,但在培养保加利亚乳杆菌时的培养效果不如对照培养基。自制蛋白胨作为氮源培养大部分乳酸菌时的培养结果要优于对照培养基,自制蛋白胨可以取代对照培养基中的部分氮源制作新的培养基,并降低培养基的制作成本。     

选择性计数双歧杆菌培养基的效果比较

随着双歧杆菌基础研究和开发应用的迅速发展,双歧杆菌活菌计数方法越来越重要,实验目的是要选择1种适于选择性计数产品中双歧杆菌菌落数的培养基。主要采用菌落技术方法,比较了常用的8种选择性培养基对7种产品中双歧杆菌的选择性计数效果。结果表明,以改良MRS-X-Gal琼脂培养基上形成的双歧杆菌菌落数最高,且菌落特征明显,易于计数,是优选出的效果较好的选择性计数培养基。     

保加利亚乳杆菌番茄复合汁增菌培养基的优选研究

研究了在番茄汁基础培养基中添加不同营养物质对保加利亚乳杆菌生长的影响,进一步采用正交试验优化筛选了保加利亚乳杆菌L.b-S1的增殖培养基。结果表明,在番茄汁基础培养基中添加胰蛋白胨、酵母膏、碳酸钙可显著促进试验菌株的细胞生长(P<0.01);利用L933正交试验筛选出增殖培养基的最佳配比为:在番茄汁基础培养基中添加0.5%酵母膏、1.0%胰蛋白胨、0.3%碳酸钙;试验菌株在增殖培养基中经37℃培养18h,活菌数可达为2.25×1010mL-1,较液体MRS培养基的活菌数(4.98×108mL-1)提高了45.18倍,成本较液体MRS培养基降低1500元/t。为工业化大规模培养乳酸菌并研制开发直投式酸奶发酵剂提供了经济廉价的增菌培养基。     

乳酸菌的培养方法及在葡萄酒中的应用

采用109#培养基,使用不同方式对乳酸菌进行培养研究。结果表明:平板培养条件要求高,在目前条件下,几乎培养不出;斜面培养比较容易,但只能定性;液体培养能估测出最大活菌数;以上培养方式在葡萄酒中的乳酸菌检测方面都处于摸索阶段。     

乳酸菌增菌培养基筛选及干燥保护剂的选择

对促进乳酸菌生长的营养物质及冻干保护剂进行了研究,结果保加利亚杆菌、嗜热链球菌和嗜酸乳杆菌在液体培养基中菌数增到1010～1011cfu/g,经冷冻干燥后活菌数达到1010cfu/g以上.     

嗜热链球菌与保加利亚乳杆菌麦芽复合汁增菌培养基的优化筛选

研究了在麦芽汁中添加不同的营养因子对嗜热链球菌S.t-3的细胞生长量的影响,进一步采用正交试验优化筛选出S.t-3的麦芽复合汁增菌培养基,并对保加利亚乳杆菌L.b-DR和L.b-S1进行了验证性增菌试验。结果表明,S.t-3、L.b-DR和L.b-S1在麦芽汁中能进行正常的产酸代谢,大豆蛋白胨、牛肉膏、酵母膏可显著促进S.t-3的细胞生长(P<0.05);K2HPO4不仅可以促进菌体增殖,而且还可缓冲基质pH值的变化,避免了低pH值对乳酸菌的伤害;利用L9(33)正交试验,筛选出S.t-3的麦芽复合汁增菌培养基最佳配比为:在10%的麦芽汁中添加0.5%大豆蛋白胨、0.5%酵母膏、1%牛肉膏、0.2%K2HPO4;在麦芽复合汁增菌培养基中,S.t-3、L.b-DR和L.b-S1,37℃恒温培养16 h,活菌数分别为2.42×109cfu/mL、2.85×109cfu/mL和4.81×109cfu/mL,与液体MRS培养基的活菌数相当,成本较MRS培养基降低1 000元人民币/t。     

Antimicrobial potential of immobilized Lactococcus lactis subsp. lactis ATCC 11454 against selected bacteria

Immobilization of living cells of lactic acid bacteria could be an alternative or complementary method of immobilizing organic acids and bacteriocins and inhibit undesirable bacteria in foods. This study evaluated the inhibition potential of immobilized Lactococcus lactis subsp. lactis ATCC 11454 on selected bacteria by a modified method of the agar spot test. L. lactis was immobilized in calcium alginate (1 to 2%)-whey protein concentrate (0 and 1%) beads. The antimicrobial potential of immobilized L. lactis was evaluated in microbiological media against pathogenic bacteria (Escherichia coli, Salmonella, and Staphylococcus aureus) or Pseudomonas putida, a natural meat contaminant, and against seven gram-positive bacteria used as indicator strains. Results obtained in this study indicated that immobilized L. lactis inhibited the growth of S. aureus, Enterococcus faecalis, Enterococcus faecium, Lactobacillus curvatus, Lactobacillus sakei, Kocuria varians, and Pediococcus acidilactici. Only 4 h of incubation at 35 degrees C resulted in a clear inhibition zone around the beads that increased with time. With the addition of 10 mM of a chelating agent (EDTA) to the media, results showed growth inhibition of E. coli; however, P. putida and Salmonella Typhi were unaffected by this treatment. These results indicate that immobilized lactic acid bacteria strains can be successfully used to produce nisin and inhibit bacterial growth in semisolid synthetic media.     

直投式泡菜乳酸菌发酵剂培养基的优化及离心条件的探索

根据番茄汁、马铃薯汁和胡萝卜汁的营养条件和乳酸菌的营养要求,通过正交试验,确定泡菜用肠膜明串珠菌和乳酸乳球菌的最佳培养基。试验结果为:肠膜明串珠菌的最佳培养基为:30%番茄汁、25%马铃薯汁、10%胡萝卜汁;乳酸乳球菌的最佳培养基为:25%番茄汁、35%马铃薯汁、15%胡萝卜汁。结果表明:肠膜明串珠菌和乳酸乳球菌分别以此培养基在34℃下培养24 h,其活菌数可达109cfu/mL以上,大大降低了培养基的成本。选择的最佳离心条件为:4 000 r/min的转速下离心20 min,在此条件下离心存活率最高,为制备直投式发酵剂提供了理论依据。     

益生菌的筛选及其发酵特性研究

为获得性能优良的益生菌生产菌株,通过乳酸菌的溶钙圈筛选,耐酸、耐胆盐检测及体外抗氧化和分解胆固醇能力测试进行了菌株的选育;对筛选菌株进行16S rRNA基因测序及生理生化特性鉴定;采用正交试验优化培养基配方和发酵条件。结果表明,从牛奶储罐中分离、筛选到一株各项性能优良的菌株,编号为SX68,经鉴定其为植物乳杆菌（Lactobacillus plantarum）。优化培养基配方为：蛋白胨10 g/L,牛肉膏10 g/L,酵母提取物5 g/L,磷酸氢二钾3 g/L,柠檬酸氢二胺4 g/L,乙酸钠5 g/L,葡萄糖30 g/L,吐温-80 1 mL/L,MgSO4·7H2O 0.58 g/L,MnSO4·4H2O 0.25 g/L,pH 6.4;最佳发酵条件为：起始pH 6.5,发酵温度35 ℃,接种量20 mL/L,溶氧量＜100 mL/L,搅拌转速50 r/min,罐压0.03 MPa。在此优化条件下,菌株SX68最高发酵生物量（OD600 nm值）为15.68,活菌数为9.6×1012 CFU/mL,可为其用于益生菌生产奠定基础。     

用于乳酸菌分离鉴定的几种培养基的筛选及应用

发酵乳产品中益生菌活菌数的正确评价,对保障发酵乳制品的质量和功效具有重大意义。本研究通过对三种不同的益生菌在五种不同的培养基上的生长状况进行了评价和观察,结果发现嗜热链球菌和嗜酸乳杆菌在改良TJA培养基上生长状况很好,瑞士乳杆菌在溴甲酚绿指示剂培养基上长势良好。研究结果为以这些菌种研究开发新型发酵乳产品提供了技术和品质的保证,也为益生菌及益生菌制品深入研究打下了基础。     

Physiological adaptation of Escherichia coli after transfer onto refrigerated ground meat and other solid matrices: A molecular approach

Bacteria on meat are subjected to specific living conditions that differ drastically from typical laboratory procedures in synthetic media. This study was undertaken to determine the behavior of bacteria when transferred from a rich-liquid medium to solid matrices, as is the case during microbial process validation. Escherichia coli cultured in Brain-Heart Infusion (BHI) broth to different growth phases were inoculated in ground beef (GB) and stored at 5°C for 12 days or spread onto BHI agar and cooked meat medium (CMM), and incubated at 37°C for several hours. We monitored cell densities and the expression of σ factors and genes under their control over time. The initial growth phase of the inoculum influenced growth resumption after transfer onto BHI agar and CMM. Whatever the solid matrix, bacteria adapted to their new environment and did not perceive stress immediately after inoculation. During this period, the σ(E) and σ(H) regulons were not activated and rpoD mRNA levels adjusted quickly. The rpoS and gadA mRNA levels did not increase after inoculation on solid surfaces and displayed normal growth-dependent modifications. After transfer onto GB, dnaK and groEL gene expression was affected more by the low temperature than by the composition of a meat environment.     

培养条件和果汁种类对脂环酸芽孢杆菌生长的影响

脂环酸芽孢杆菌是造成巴氏灭菌果汁腐败的重要细菌之一。鉴于目前脂环酸芽孢杆菌的培养方法尚未统一且污染特征不明确,本研究考察了pH、7种培养基和9种果汁对其生长的影响,同时采用固相微萃取(SPME)和气相色谱(GC)-质谱(MS)技术检测了该菌的主要代谢产物愈创木酚和2,6-二溴苯酚在果汁中的释放情况。结果表明,脂环酸芽孢杆菌在pH4.0时生长情况最好,pH2.5时生长较差,pH6.0~7.0时最差。AAM培养基和BAT培养基较其他5种培养基(YSG培养基、K氏培养基、SK培养基、PDB培养基和营养肉汤培养基)更适合用来培养脂环酸芽孢杆菌。脂环酸芽孢杆菌接种到9种果汁中后生长差异明显,在葡萄汁和橙汁中生长情况最好,细菌数量分别为1.5×104 CFU/mL和8.5×103 CFU/mL;在菠萝汁和西柚汁中生长缓慢,细菌数量分别为4.4×102 CFU/mL和1.9×102 CFU/mL。此外,9种果汁接种脂环酸芽孢杆菌后均未检测出2,6-二溴苯酚;但是,除葡萄汁外的8种果汁均检测出愈创木酚,浓度在8.6~23.9 μg/L之间。     

Enhanced regeneration of rice (Oryza sativa L.) embryogenic callus by light irradiation in growth phase

The effect of light irradiation on the growth and regeneration of embryogenic rice calli was investigated. Rice calli grew slightly better in the light than in the dark during the growth stage. When calli subcultured under light irradiation were transferred into a liquid regeneration culture system, the number of plantlets with shoots regenerated from calli subcultured in the light was higher than in the case of those subcultured in the dark, whereas there was no obvious difference between the light and dark subcultures when a solid medium was used for the regeneration. The number of regenerated plantlets increased with increasing light intensity up to 2000 lx, but remained the same when the light intensity was raised further. The maximum number of regenerated plantlets was obtained under a photoperiod of 16 h/d. About 8800 plantlets per liter-medium were regenerated from light-cultured calli, which is 1.5 times more than the number regenerated from calli grown in the conventional dark culture.     

面包贮存过程中微生物的变化

模拟小作坊面包房中面包的生产环境,以添加和不添加防腐剂丙酸钙的面包为研究对象,通过保鲜袋密封包装贮存在温度为30℃、湿度70%的环境下,对比研究两种产品在贮存过程中霉菌和细菌数目的变化。实验结果表明,面包在贮存过程中,霉菌和细菌数目都快速增长,但添加防腐剂丙酸钙的面包,其霉菌和细菌数目增长速度都相对较慢。面包贮存2 d,虽然没有菌斑出现,但霉菌和细菌数目已经超过国家标准规定。     

蔬菜发酵菌种的筛选及发酵特性

为了选择适合蔬菜发酵的发酵菌种,本研究从四川泡菜老汤中分离的6 种乳酸菌Lactobacillus plantarum、Lactobacillus fermentum、Lactobacillus brevi、Lactobacillus pentosus、Leuconostoc mesenteroides、Lactobacillus lactics筛选发酵菌种。6 种乳酸菌接入亚硝酸盐的MRS培养液中,6 种乳酸菌还原亚硝酸盐的大小顺序为Lactobacilluspentosus＞Lactobacillus plantarum＞Leuconostoc mesenteroides＞Lactobacillus fermentum＞Lactobacillus lactics＞Lactobacillus brevis。以pH值降低的速率为发酵速率,Lactobacillus plantarum、Lactobacillus pentosus、Leuconostocmesenteroides这3 种发酵剂的发酵速率较其他3 种快,并且通过乳酸菌的全细胞蛋白电泳实验得出此3 种乳酸菌在甘蓝发酵过程中能够成为优势菌。从乳酸菌还原亚硝酸盐的能力、发酵速率、发酵菌种的生存能力（是否能成为优势菌）的实验结果表明Lactobacillus plantarum、Lactobacillus pentosus、Leuconostoc mesenteroides这3 种乳酸菌作为蔬菜发酵的发酵剂。通过对3 种发酵菌种发酵特性的研究可知,Leuconostoc mesenteroides较另两种生长周期短,稳定期维持时间短,很快进入衰退期。Lactobacillus plantarum菌较Lactobacillus pentosus、Leuconostoc mesenteroides耐酸,Leuconostoc mesenteroides对酸敏感。Leuconostoc mesenteroides最适生长温度为30 ℃,Lactobacillus plantarum、Lactobacillus plantarum两种菌的最适生长温度是37 ℃。15 ℃条件下Leuconostoc mesenteroides的光密度（OD600 nm）值很低,说明Leuconostoc mesenteroides较Lactobacillus plantarum、Lactobacillus pentosus对低温敏感。