冻干乳酸菌菌种增菌培养基增殖因子的优化

发酵剂是影响整个酸奶生产的关键因素之一,冷冻干燥乳酸菌发酵剂的使用提高了企业产品质量,避免了因微生物力量不足而造成的菌种质量不佳等问题。在基础培养基的基础上确定了嗜热链球菌(Streptococcus therm ophilus,S.t)和保加利亚乳杆菌(Lactobacil-lus bulgaricus,L.b)的增菌配方分别为:S.t(平菇浸汁14mL、胡萝卜汁10mL、玉米浆0.6mL、Vc0.2g)和L.b(啤酒10mL、番茄汁10mL、胡萝卜汁15mL、平菇浸汁16mL),同时测定了其最佳培养时间。     

万古霉素产生菌发酵培养基及发酵条件的优化

通过单因素分析和正交试验,对万古霉素产生菌的发酵培养基和发酵条件进行了研究,确定最佳的发酵培养基配方为葡萄糖2.0%,淀粉3.0%,豆粕1.8%,大豆粉2.2%,氯化钠0.2%,碳酸钙0.2%,与原培养基配方相比,优化后万古霉素的摇瓶发酵效价提高了11.2%。同时优化了部分发酵条件,即二级种接种量为10%,溶氧为摇床转速220 r/min时250 mL摇瓶装液量为25 mL。将优化后的发酵工艺进罐验证,其保持了较高的适应性和连续性。     

CpG基序重组菌发酵培养基的优化

目的:为提高CpG基序重组菌的发酵水平,降低CpG重组质粒的生产成本,运用响应面法优化CpG重组菌发酵培养基。方法:利用Plackett-Burman试验筛选出影响发酵水平的3个最显著因素:糖蜜、玉米浆和工业蛋白胨。然后用响应面设计试验并优化得到最显著因素的最佳浓度,并进一步通过发酵试验验证优化后的培养基。结果:得到一组具有较高菌浓及质粒产量且价格低廉的发酵用培养基:糖蜜4.5g/L,玉米浆8.5g/L,工业蛋白胨8.5g/L,甘油10mL/L,KH2PO41.5g/L,K2HPO42.3g/L,MgSO4.7H2O 0.25g/L,在此培养条件下,OD600实测值为0.6771,理论值为0.6643,两者接近,与标准LB培养基相比,质粒产量提高了15%左右。结论:最终筛选到的培养基具有较高的性价比。     

L-色氨酸基因工程菌发酵培养基配方优化研究

[目的]对L-色氨酸基因工程菌液态发酵的培养基进行优化。[方法]通过P-B试验,筛选出对基础发酵培养基的发酵液中L-色氨酸浓度影响显著的因素,进一步通过最陡爬坡试验、B-B试验对影响显著的因素进行优化。在此基础上,确定最佳的发酵培养基配方。[结果]酵母粉、Fe SO4·7H2O、KH2PO4对发酵液中L-色氨酸浓度的影响显著;最佳培养基配方为:Glucose 25.0 g/L,酵母粉4.5 g/L,(NH4)2SO49.0 g/L,Mg SO44.5 g/L,柠檬酸钠2.0 g/L,Fe SO4·7H2O 96.1 m g/L,KH2PO41.2 g/L。[结论]根据此配方进行验证实验,发酵液中L-色氨酸浓度可达2.25 g/L。     

透明质酸产生菌的选育及发酵培养基的优化

将实验室保存UVD-34透明质酸产生菌再进行超声波处理,挑选出了一株透明质酸产量较高的菌,并对其发酵培养基进行初步优化。结果表明当可溶性淀粉质量分数为2%,复合氮源为3%,碳酸氢钠为0.1%时,其透明质酸的产量可达4.59 g.L-1,比优化前提高了1.29倍。该突变株值得进一步研究。     

双歧杆菌培养基的优化

针对双歧杆菌的营养需要,分别采用单因素试验和正交试验,优化培养基成分及用量。得出最优培养基(CPT)配比:大豆蛋白胨1.67%,酪蛋白胨0.83%,乳糖0.5%,酵母浸出粉0.5%,低聚糖0.7%,胡萝卜汁15%。最后测定双歧杆菌在最优培养基中的生长曲线,并同时测定pH和吸光值的变化,确定培养终止时间为12h,菌数可达2.18×109CFU/mL,且发酵培养基具有极显著的增菌效果(p<0.01)。     

一株石油降解菌培养基的优化

目的：有效降低石油降解菌株CT-6在工业生产中的培养成本,提高培养速度。方法：利用Minitab软件,采用中心组合设计、响应面分析,以葡萄糖、蔗糖、可溶性淀粉为碳源,以硝酸铵、尿素、氯化铵为氮源,对高效降解石油菌株CT-6的培养基进行了优化。结果：当碳源葡萄糖为5.6818g/L、氮源氯化铵为3.8030g/L时,菌株CT-6培养17h,OD600达到0.615。结论：优化前后,菌体CT-6的OD600分别为0.289和0.615,提高了112.8%,说明该培养基更有利于菌株CT-6的生长。     

6种细菌菌数测定培养基的优化

考察平板计数琼脂(PCA)中不同来源的酵母浸粉对6种细菌总数测定的影响,并对培养基中酵母浸粉和胰蛋白胨的配比及含量进行了优化。优化后的培养基组分为胰蛋白胨3.0 g·L-1,酵母浸粉3.0 g·L-1,葡萄糖1.0 g·L-1,琼脂15.0 g·L-1。与市售平板计数琼脂相比,能检出的细菌总数提高6.9%。     

均匀设计法优化烟管菌产漆酶培养基

应用均匀设计、二次多项式逐步回归分析对烟管菌(Bjerkandera adusta)WZFF.W-Y11产漆酶液态发酵培养基进行优化。结果表明,培养基组成为麸皮水解液1%、淀粉24.0 g/L、葡萄糖24.0 g/L、豆饼粉4.8 g/L、NH₄Cl 3.2g/L、KH₂PO₄ 3.2 g/L、MgSO₄·7H₂O 0.2 g/L、CuSO₄ ·5H₂O 0.006 g/L,起始pH6.5,在28℃、150r/min、250mL的摇瓶培养条件下可以稳定地获得9672U/L的漆酶活力。     

均匀设计法优化烟管菌产漆酶培养基

应用均匀设计、二次多项式逐步回归分析对烟管菌(Bjerkandera adusta)WZFF.W-Y11产漆酶液态发酵培养基进行优化。结果表明,培养基组成为麸皮水解液1%、淀粉24.0g/L、葡萄糖24.0g/L、豆饼粉4.8g/L、NH4Cl3.2g/L、KH2PO43.2g/L、MgSO4.7H2O0.2g/L、CuSO4.5H2O0.006g/L,起始pH6.5,在28℃、150r/min、250mL的摇瓶培养条件下可以稳定地获得9672U/L的漆酶活力。     

不同碳源对须糖多孢菌生长发育及丁烯基多杀菌素生物合成的影响

本文研究了不同碳源对须糖多孢菌生长以及丁烯基多杀菌素生物合成的影响,通过寻找优势碳源优化发酵培养基配方,促进须糖多孢菌丁烯基多杀菌素的生物合成。试验共设11个处理,1个对照,通过单因素试验比较不同处理组菌体OD600值和丁烯基多杀菌素产量,筛选获得最优碳源及其发酵培养基配方。结果表明,除可溶性淀粉和木糖外,须糖多孢菌在9种碳源中都能进行生长,对不同构型碳源显示较好的利用率。在以半乳糖、葡萄糖、果糖和甘露糖作为碳源时具有较好的生长速率,而以甘露糖为碳源时能显著促进丁烯基多杀菌素的合成。选择甘露糖最佳添加浓度为5 g/L,须糖多孢菌最高菌体浓度和丁烯基多杀菌素产量分别是初始配方条件的1. 32倍和1. 78倍,显著提高了丁烯基多杀菌素的产量。上述结果为培养基碳源对丁烯基多杀菌素生物合成影响机制的研究及丁烯基多杀菌素大规模工业化发酵生产提供了科学依据和新的技术途径。     

Survival of orally administered isolated intestinalLactobacillus acidophilus in different parts of gastrointestinal tract of mice

A strain ofLactobacillus acidophilus (Strain HF) was isolated from human faeces. A chloramphenicol resistant strain (HFCm) and a strain (HFCmSm) restant to both chloramphenicol and streptomycin were developed from the isolated strain (HF). All the three strains showed similarin vitro susceptibility against host defence factors like gastric acid, bile salts and volatile as well as non-volatile fatty acids.In vivo tests were done by feeding these strains to mice. When the resistant strains were orally administered along with the antibiotic(s) they were stable up to 72 h     

Identification of heterofermentative lactobacilli isolated from pig faeces by numerical analysis of total soluble cell protein patterns and RAPD-PCR

AIMS: The study deals with a number of heterofermentative Lactobacillus strains isolated from pig faeces and their identification. METHODS AND RESULTS: SDS-PAGE of total soluble cell proteins and RAPD-PCR profiles were used to identify the strains isolated from pig faeces. Protein profiles obtained with SDS-PAGE revealed that 15 strains clustered at r >or= 0.78 with Lactobacillus buchneri and nine strains at r >or= 0.77 with two reference strains of Lactobacillus reuteri. The identity of the strains was confirmed with RAPD-PCR. CONCLUSIONS: Numerical analysis of protein profiles and RAPD-PCR proved valuable in the differentiation of Lactobacillus spp. isolated from pig faeces. SIGNIFICANCE: This is the first report on the association of Lact. buchneri with pig faeces.     

Biotherapeutic role of fermented milk

Fermented milk was used as therapy in infantile diarrhoea due to post-gastroenteritis syndrome. This treatment eliminated the disease in 4.0 days (mean value, SD=2.8; n=13) and allowed patients to return to free feeding according to their age. The weight percentile variation during treatment with fermented milk (15 days) was higher in the patients showing 3^rd degree malnutrition than in other children. Bacteriotherapy can restore faecal flora which has been lowered by diarrhoea. Our results showed that levels higher than 10⁶ UFC lactobacilli/g of faeces correlated with a healthy status of the children. Clinical applications of fermented milk with a mixture ofLactobacillus casei andLactobacillus acidophilus in the prevention of gastrointestinal disorders are possible.     

Use of a DNA microfluorometric assay to measure proliferative response of mink lung cells to purified TGFβ and to TGFβ activity found in prostate cell conditioned medium

Summary The proliferative response of Mv1Lu cells to purified TGFβ₁, or TGFβ-like activity released by various cells into medium conditioned over a 24-h period was quantitated by adapting a rapid DNA fluorometric assay. Acid activation of the conditioned medium allowed the amount of biologically latent versus active TGFβ to be quantitated. A neutralizing antibody specific for TGFβ_{1, 1.2, and 2.0} completely blocked the growth inhibition observed treating Mv1Lu cells with either purified TGFβ₁ or medium containcing secreted TGFβ-like activity conditioned by DU145 prostate cells. In contrast to other assays commonly used to measure TGFβ activity, the proliferative response is related directly to DNA content rather than as a reflection of enzymatic activity or incorporation of³H-thymidine. The necessity for radioactive isotope usage has been eliminated, and the biological response can be quantitated over a period of days.     

Hybridization between escaped domestic and wild American mink (Neovison vison)

The release of domesticated organisms into natural populations may adversely affect these populations through predation, resource competition, and the introduction of disease. Additionally, the potential for hybridization between wild and domestic conspecifics is of great concern because it can alter the evolutionary integrity of the affected populations. Wild American mink ( Neovison vison ) populations may be threatened not only by competition for resources with domestic mink originating from farms, but by breeding with such escapees. Using 10 microsatellite loci, we genotyped mink from Ontario, Canada, sampled from two farms, two putatively mixed populations in regions surrounding the mink farms, and two wild populations with no recent history of mink farming. Using individual-based Bayesian population assignment, we identified four population clusters, including one wild, and three domestic populations. The latter were not clustered by farm but rather by distinct line-bred colour phases. Population clustering also identified domestic and hybrid mink in the free-ranging populations. Nearly two-thirds of the mink sampled in the two putatively mixed populations (78% and 43%) were either farm escapees or descendants of escapees. Principal components analysis of allele frequencies supported our Bayesian assignment results. The power of our assignment test was assessed using simulated hybrid genotypes which suggested that our overall correct classification rate was 96.2%. The overwhelming presence of domestic animals and their hybridization with mink in natural populations is of great concern for the future sustainability of wild mink populations.     

Microbial contamination of fuel ethanol fermentations

Microbial contamination is a pervasive problem in any ethanol fermentation system. These infections can at minimum affect the efficiency of the fermentation and at their worse lead to stuck fermentations causing plants to shut down for cleaning before beginning anew. These delays can result in costly loss of time as well as lead to an increased cost of the final product. Lactic acid bacteria (LAB) are the most common bacterial contaminants found in ethanol production facilities and have been linked to decreased ethanol production during fermentation. Lactobacillus sp. generally predominant as these bacteria are well adapted for survival under high ethanol, low pH and low oxygen conditions found during fermentation. It has been generally accepted that lactobacilli cause inhibition of Saccharomyces sp. and limit ethanol production through two basic methods; either production of lactic and acetic acids or through competition for nutrients. However, a number of researchers have demonstrated that these mechanisms may not completely account for the amount of loss observed and have suggested other means by which bacteria can inhibit yeast growth and ethanol production. While LAB are the primary contaminates of concern in industrial ethanol fermentations, wild yeast may also affect the productivity of these fermentations. Though many yeast species have the ability to thrive in a fermentation environment, Dekkera bruxellensis has been repeatedly targeted and cited as one of the main contaminant yeasts in ethanol production. Though widely studied for its detrimental effects on wine, the specific species–species interactions between D. bruxellensis and S. cerevisiae are still poorly understood.     

乳酸菌与结肠癌

摘要:流行病学调查表明,结肠癌的发病率逐年增高。结肠癌的发病是多因素协同作用的结果,这使得对结肠癌的预防和治疗都面临困境。研究普遍认为人体肠道微生态系统的平衡是预防结肠癌的关键,而摄入乳酸菌可起到维持肠道微生物菌群平衡的作用。因此,乳酸菌的生物学功能和抗肿瘤作用日渐受到研究人员的关注。本文结合我们课题组的研究成果,从结肠癌的发病原因着手,详述了乳酸菌抑制结肠癌的可能途径或机制,最后总结了乳酸菌各成分及其代谢产物在潜在抑制结肠癌过程中发挥的作用。     

Danish free-ranging mink populations consist mainly of farm animals: Evidence from microsatellite and stable isotope analyses

Two methods were used to separate free-ranging mink Mustela vison into wild mink and escaped farm mink. Analysis of stable carbon isotopes was performed on teeth and claws of 226 free-ranging mink from two areas in Denmark. A classification based on empirical data resulted in three groups (n=213); 47% were newly escaped farm mink and another 31% had been born in farms and lived in nature for more than ca. 2 months. The remaining 21% may or may not have been born in nature, but they had been free ranging for more than a year and were thus considered wild. A genetic analysis by means of microsatellites was performed on a subsample of the trapped mink (86 individuals) and on 70 farm mink, in order to assess the proportion of escaped farm mink in the free-ranging population. Strong genetic evidence for a high percentage of escaped farm mink in the free-ranging population (86%) was found, in agreement with the carbon isotope results. Both methods can be used to distinguish between farm and wild mink, but whereas microsatellites can only say whether a given mink originated from a farm or not, carbon isotopes can give some more detail on the period of time that a farm mink has been living in natural habitats. The high proportion of escaped farm mink in the Danish nature could have serious implications for the preservation of other vulnerable species and should be carefully considered when designing conservation strategies.