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A method was developed to follow a lactic acid bacterial strain, Enterococcus faecium Cernelle 68, with respect to adhesion, multiplication, colonization, and persistence in the digestive tract of mink. Also the spread of the strain in the cage was examined. When adding 5 × 109 c.f.u. of a rifampicin resistant mutant per kg feed, high viable counts were registered throughout the digestive tract, apart from the oesophagus. Counts were increasing in the aboral direction, suggesting some multiplication in the intestine. It was possible to detect the strain in the intestinal tract 4 days after discontinuation of administration. Neither culture nor scanning electron microscopy gave evidence to suggest that E. faecium Cernelle 68 adhered to the mucosa. The spread of the E. faecium strain was observed in the environment. Counts of E. coli, lactobacilli, staphylococci, and Clostridia were low, and none of these bacteria were constant findings. 相似文献
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Summary: The micro-ecology of block cured, sliced, vacuum packed bacon has been studied during storage at 20 and 30°; high salt (8–12% NaCl, based on the aqueous phase) and low salt (5–7% NaCl) bacon were used. The dominant flora of all samples during the first 9 days' storage comprised catalase positive cocci. They persisted in the high salt bacon but, under lower salt conditions, group D streptococci and motile lactic acid bacteria became dominant.
Of the chemical changes studied, proteolysis, lipolysis and reduction of nitrate and nitrite were due largely to coagulase negative subgroup II staphylococci. Micrococci which predominated at 20° were capable of reducing nitrate to nitrite but of only slightly increasing free amino or fatty acids.
Inoculation of low count bacon with subgroup II staphylococci confirmed that this group was responsible for putrefaction in low salt bacon stored at temperatures above 20°. Similarly micrococci which tend to delay spoilage did not contribute much to the off odours and it was thought that the heterofermentative catalase negative organisms could contribute to typical sour spoilage. 相似文献
Of the chemical changes studied, proteolysis, lipolysis and reduction of nitrate and nitrite were due largely to coagulase negative subgroup II staphylococci. Micrococci which predominated at 20° were capable of reducing nitrate to nitrite but of only slightly increasing free amino or fatty acids.
Inoculation of low count bacon with subgroup II staphylococci confirmed that this group was responsible for putrefaction in low salt bacon stored at temperatures above 20°. Similarly micrococci which tend to delay spoilage did not contribute much to the off odours and it was thought that the heterofermentative catalase negative organisms could contribute to typical sour spoilage. 相似文献
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Ronl Visser Wilhelm H. Holzapfel Johannes J. Bezuidenhout Johannes M. Kotz 《Applied microbiology》1986,52(3):552-555
A variety of lactic acid bacteria, isolated from plant surfaces and plant-associated products, were found to be antagonistic to test strains of the phytopathogens Xanthomonas campestris, Erwinia carotovora, and Pseudomonas syringae. Effective “in vitro” inhibition was found both on agar plates and in broth cultures. In pot trials, treatment of bean plants with a Lactobacillus plantarum strain before inoculation with P. syringae caused a significant reduction of the disease incidence. 相似文献
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Microbiology - Lactic acid bacteria (LAB) are widely used in fermentation processes for the preparation of various foodstuffs, including dairy, meat and vegetable products. In the course of... 相似文献
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食品级乳酸菌表达系统研究进展 总被引:2,自引:0,他引:2
乳酸菌表达系统是近几年发展起来的食品级高效表达系统。乳酸菌具有益生菌特征,因此该表达系统与其他细菌表达系统相比有很多优点。介绍了糖诱导表达系统、噬菌体Φ31爆发式诱导的表达系统、乳链球菌素调控表达系统、温控表达系统等的研究进展,以及这些系统的应用前景。 相似文献
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乳酸菌食品级基因表达系统 总被引:13,自引:0,他引:13
酸菌是一类重要工业菌株。最近,乳酸菌遗传学和分子生物学的研究取得长足进步,导致发展了乳酸菌食品级基因表达系统。通过介绍乳酸菌食品级基因表达系统的基本要求、食品级选择性标记、食品级诱导物及该系统的研究进展,展示了乳酸菌食品级基因表达系统的建立对研究乳酸菌的基因表达调控和它的深层次的开发利用所具有的重要意义。 相似文献
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Lactic acid bacteria (LAB) is mainly used in food fermentation. In addition, LAB fermentation technology has been studied in the development of industrial food additives, nutrients, or enzymes used in food processing. In the field of red biotechnology, LAB is approved and is generally recognized as a safe organism and is considered safe for biotherapeutic treatments. Recent clinical trials have demonstrated the medicinal value of therapeutic recombinant LAB and the suitability of innate mechanisms of secretion and anchoring for therapeutic applications such as antibody or vaccine production. However, the gram‐positive phenotypic trait of LAB creates challenges for genetic modifications when compared to other conventional workhorse bacteria, resulting in exclusive developments of genetic tools for engineering LAB. In this review, several distinct approaches in gene expression for engineering LAB are discussed. 相似文献
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猪源乳酸菌产乳酸及其抑菌特性研究 总被引:13,自引:0,他引:13
研究了5株(L1、12、L3、L5和L7)分离自仔猪肠道的乳酸菌的产乳酸能力及抑菌特性。结果表明:L5菌株产乳酸的速度最快,培养液中乳酸含量最高,L5菌株培养液pH值的下降速度最快,终末pH值最低,而L1菌株产乳酸的速度最慢,培养液乳酸含量最低。5株乳酸菌对大肠杆菌K88、K99、987P、O141和大肠杆菌E1及金黄色葡萄球菌均有不同程度的抑制作用;排除酸的影响后仍有22%~53%抑菌效果;经热处理后保持有92%以上的抑菌效果;蛋白酶处理后保持85%以上的抑菌效果。 相似文献
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We designed an expression and export system that enabled the targeting of a reporter protein (the staphylococcal nuclease Nuc) to specific locations in Lactococcus lactis cells, i.e., cytoplasm, cell wall, or medium. Optimization of protein secretion and of protein cell wall anchoring was performed with L. lactis cells by modifying the signals located at the N and C termini, respectively, of the reporter protein. Efficient translocation of precursor (approximately 95%) is obtained using the signal peptide from the lactococcal Usp45 protein and provided that the mature protein is fused to overall anionic amino acids at its N terminus; those residues prevented interactions of Nuc with the cell envelope. Nuc could be covalently anchored to the peptidoglycan by using the cell wall anchor motif of the Streptococcus pyogenes M6 protein. However, the anchoring step proved to not be totally efficient in L. lactis, as considerable amounts of protein remained membrane associated. Our results may suggest that the defect is due to limiting sortase in the cell. The optimized expression and export vectors also allowed secretion and cell wall anchoring of Nuc in food-fermenting and commensal strains of Lactobacillus. In all strains tested, both secreted and cell wall-anchored Nuc was enzymatically active, suggesting proper enzyme folding in the different locations. These results provide the first report of a targeting system in lactic acid bacteria in which the final location of a protein is controlled and biological activity is maintained. 相似文献
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一组鸡源乳酸菌产乳酸及其耐受特性研究* 总被引:3,自引:0,他引:3
研究了12株(K9、D17、C1、C12、D11、D14、C2、D9、K6、C21、D1和D7)分离自肉鸡肠道的乳酸菌的产乳酸能力及其中3株产酸能力强的菌株的耐受特性。12株乳酸菌产乳酸结果表明:12h内,K6产乳酸速度最快,其次为K9和C1,24h时,D17乳酸浓度最高,48h时C1终乳酸浓度最高。K9、D17和C1的耐受试验结果表明:C1菌株耐酸能力最强,pH2时,C1菌株培养3h后还能检测到活菌,D17和K9菌株培养1h后就已经检测不到活菌。在胆盐浓度0.08%-0.40%范围内,C1、D17和K9均有一定的耐受能力,随着胆盐浓度的升高,C1、D17和K9的存活数呈现缓慢的下降趋势。3株菌中D17耐热能力最强,经80%处理后仍有10^4.9/mL存活数,而K9和C1已检测不到活菌;C1对热最敏感,65℃处理后存活数由10^8/mL降为10^3/mL。 相似文献
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Recent research in the area of importance of microbes has revealed the immense industrial potential of exopolysaccharides
and their derivative oligosaccharides from lactic acid bacteria. However, due to lack of adequate technological knowledge,
the exopolysaccharides have remained largely under exploited. In the present review, the enormous potentials of different
types of exopolysaccharides from lactic acid bacteria are described. This also summarizes the recent advances in the applications
of exopolysaccharides, certain problems associated with their commercial production and the remedies. 相似文献
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应用于乳酸菌的非抗生素抗性选择标记系统 总被引:3,自引:0,他引:3
乳酸菌是一类重要的安全型微生物,在免疫载体疫苗开发及食品菌株改良等医疗、食品领域均有广泛的应用.非抗生素抗性选择标记是乳酸菌基因工程菌株构建中必不可少的关键组成部分,也是目前乳酸菌研究的前沿和热点.根据筛选时质粒和受体菌之间的表型关系及特征,主要分为显性选择标记、互补型选择标记、显性/互补型选择标记、双质粒选择标记4大类.其中显性选择标记中的细菌素抗性/免疫性选择标记及互补型选择标记中的糖类选择标记均有较大的发展潜力及应用空间;双质粒选择标记系统构建的筛选过程新颖独特,为整个选择标记系统的发展开辟了新的途径及思路. 相似文献