腌鱼中硝酸盐还原菌的筛选及系统发育分析

微生物作用是硝酸盐还原成亚硝酸盐的主要原因,而亚硝酸盐在一定条件下会合成强致癌物质——亚硝胺类化合物,存在潜在的食品安全问题。从浙江省特色腌制水产品腌鱼中分离形态颜色各异的菌株,应用硝酸盐还原实验快速筛选具有硝酸盐还原能力的菌株,进而对筛选的菌株进行形态观察、革兰氏染色、生理生化与分子生物学鉴定。最终筛选出有两株菌具有硝酸盐还原性,F-1菌株为Psychrobacter glacincola,F-2菌株为Psychrobacter faecalis。      

腌鱼中硝酸盐还原菌的筛选及系统发育分析

微生物作用是硝酸盐还原成亚硝酸盐的主要原因,而亚硝酸盐在一定条件下会合成强致癌物质——亚硝胺类化合物,存在潜在的食品安全问题。从浙江省特色腌制水产品腌鱼中分离形态颜色各异的菌株,应用硝酸盐还原实验快速筛选具有硝酸盐还原能力的菌株,进而对筛选的菌株进行形态观察、革兰氏染色、生理生化与分子生物学鉴定。最终筛选出有两株菌具有硝酸盐还原性,F-1菌株为Psychrobacter glacincola,F-2菌株为Psychrobacter faecalis。     

发酵红皮萝卜中硝酸还原菌的分离筛选

研究了发酵红皮萝卜中细菌和大肠杆菌数量与亚硝酸盐含量变化的规律,从中分离得到10株菌株,通过硝酸盐还原能力的测定,筛选出9株具有硝酸盐还原能力的菌株,其中E5和E6两个菌株硝酸盐还原能力最强,并测定了2个菌株硝酸还原酶(NR)的酶活及pH对酶活的影响。进而对筛选的E5、E6两个菌株进行了分子生物学鉴定。结果表明,E5为阴沟肠杆菌(Enterobacter cloacae),E6为克雷伯氏菌(Klebsiella oxytoca)。     

芹菜贮藏过程中亚硝酸含量与微生物动态关系研究

目的:分析不同初加工方式和贮藏温度下芹菜中亚硝酸盐含量和菌落总数,研究亚硝酸盐含量与微生物之间的动态关系。方法:检测芹菜在保持原状、颗粒状、粉末状3种初加工方式和1、4、8℃3种贮藏温度下亚硝酸盐含量和菌落总数,分析高亚硝酸盐样品中代表性菌株的硝酸盐还原特性。结果:(1)芹菜在8℃下贮藏时最早检出亚硝酸盐,且亚硝酸盐积累量最大;(2)粉末状芹菜最早检测到亚硝酸盐,亚硝酸盐最大积累量为240 mg/kg(以N计);(3)菌落总数达到107 cfu/g亚硝酸盐开始检出,菌落总数达到108 cfu/g时芹菜中亚硝酸盐含量达到峰值;(4)菌株分析发现6株细菌具有硝酸盐还原特性,为挑取总菌落数的6/10。结论:芹菜中菌落总数变化与亚硝酸含量变化存在动态关系,初步推断硝酸盐还原菌大量繁殖导致了芹菜中亚硝酸盐的积聚。     

腌制酸菜中亚硝酸盐降解菌的筛选及其降解特性研究

通过划线分离、格里斯试剂比色法、紫外分光光度法测定,从陕北地区的酸菜水中筛选得到11株亚硝酸盐降解菌,经过测定,菌株SQ-4可以高效降解亚硝酸盐,降解率可达97.60%。通过检测硝酸盐和VC含量可知,该菌株并未通过代谢活动将亚硝酸盐转化为硝酸盐,同时产生了一定量的VC。      

陕北酸菜中亚硝酸盐降解菌研究初报

试验通过划线分离、格里斯试剂比色法、紫外分光光度法,测定从陕北地区的酸菜水中筛选得到11株亚硝酸盐降解菌,经过测定,菌株SQ-4可以高效降解亚硝酸盐,降解率可达97.60%。通过对硝酸盐和VC含量的检测得知,该菌株并未将亚硝酸盐转化为硝酸盐,并在代谢过程中产生了VC。     

腌制酸菜中亚硝酸盐降解菌的筛选及其降解特性研究

通过划线分离、格里斯试剂比色法、紫外分光光度法测定,从陕北地区的酸菜水中筛选得到11株亚硝酸盐降解菌,经过测定,菌株SQ-4可以高效降解亚硝酸盐,降解率可达97.60%。通过检测硝酸盐和VC含量可知,该菌株并未通过代谢活动将亚硝酸盐转化为硝酸盐,同时产生了一定量的VC。     

贵州酸肉中具有高亚硝酸盐降解和耐受能力乳酸菌的筛选与鉴定

从贵州自然发酵的酸肉中分离出19株乳酸菌,选择在MRS培养基中培养24 h的降亚硝酸盐能力最强的3株乳酸菌,经16S r DNA分子鉴定为植物乳杆菌CMRC 3、戊糖片球菌CMRC 7和植物乳杆菌CMRC 19。在模拟肉类发酵的条件下,研究其降解、耐受亚硝酸盐和硝酸盐的能力。3株乳酸菌都具有较好的亚硝酸盐降解能力,发酵120 h后分别降解了65.7%~86.3%的亚硝酸盐;然而它们的硝酸盐降解能力都不显著。CMRC 7和CMRC 19耐受亚硝酸盐的性能最强,最高活菌数分别为8.20lg(CFU/m L)和8.11lg(CFU/m L);这3株菌都具有较好的硝酸盐耐受性,最高活菌数分别为8.21,7.93lg(CFU/m L)和8.20lg(CFU/m L)。试验结果表明,从酸肉中筛选出的这3株乳酸菌都有较强的亚硝酸盐降解能力,同时也有较好的硝酸盐和亚硝酸盐耐受性能,可开发成肉类专用发酵剂。     

降亚硝酸盐乳酸菌的鉴定及生长特性的研究

从传统发酵食品中分离乳酸菌,筛选鉴定降解亚硝酸盐能力较强的菌株,并研究其在白菜汁培养基中的生长及产酸情况,为制作泡菜发酵剂储备优良菌株。结果分离了144株乳酸菌,并获得5株亚硝酸盐降解率在99%以上的菌株,经鉴定菌株Mao21.1和Mao6.2为戊糖乳杆菌,Wang3.1和Mao20.1为植物乳杆菌,Lin2.4为戊糖片球菌。5株菌在白菜汁培养基中生长4h后,各菌株培养液的pH均快速下降;培养20h后,除菌株Mao21.1外,其他菌株培养液pH均降到3.5以下;对数生长末期菌株Mao6.2和Lin2.4活菌数达到108cfu/mL,该两株菌可作为制作泡菜发酵剂的储备菌株。     

石榴皮多酚提取物对泡菜中亚硝酸盐消减机理研究

文章中研究了石榴多酚提取物(PPE)对硝酸盐还原菌和乳酸菌及其还原硝酸盐和降解亚硝酸盐能力的影响.结果显示,该提取物对硝酸盐还原菌具有较强的抑制作用;在较低浓度时可促进乳酸菌的生长,在较高浓度时却抑制乳酸菌的生长;PPE可抑制硝酸盐还原酶的活性,降低硝酸盐还原菌还原硝酸盐的作用,提高乳酸菌降解亚硝酸盐的能力.     

Technological activities of Staphylococcus carnosus and Staphylococcus simulans strains isolated from fermented sausages

The aim of this study was to determine the technological properties of 2 strains of Staphylococcus simulans (Ssm12, Ssm21) and 4 strains of S. carnosus (SC28, SC31, SC54 and SC55) for the selection of a potential starter cultures to employ in the processing of dry fermented sausages. The strains were studied to evaluate nitrate reductase, proteolytic, lipolytic, decarboxylase and antioxidant activities as well as growth ability at different temperatures, pH and NaCl concentrations. Nitrate reductase activity was determined at 15, 20 and 30 °C. By spectrophotometric method all the strains were able to reduce nitrate to nitrite at the different temperatures but these results were not confirmed by the agar plate method. Antioxidant and lipolytic activities were evaluated by spectrophotometric assay. All the strains showed antioxidative enzymes superoxide dismutase (SOD) and catalase whereas all appeared unable to hydrolyse pork fat. Proteolytic activity was determined by agar plate method, spectrophotometric assay (OPA) and sodium dodecyl sulphate gel-electrophoresis (SDS–PAGE) and all strains appeared to be able to hydrolyse sarcoplasmic proteins but not myofibrillar proteins. Finally, all the strains grew at 15 and 20 °C, in presence of 10%, 15% and 20% of NaCl and at pH 5.0 and 5.5 and were unable to produce histamine, cadaverine and putrescine. The results showed that all strains studied possess useful technological activities that would make them eligible as a good starter cultures for fermented sausages.     

白肋烟烟叶氮同化能力及其对硝酸盐积累的影响

为明确白肋烟烟叶硝酸盐积累的主要原因,以烤烟为对照,研究白肋烟硝酸盐同化作用及其对硝酸盐积累的影响。结果表明:增施5倍氮素后,白肋烟较烤烟干物质积累量与烤烟相近;在相同供氮条件下,白肋烟烟叶硝酸盐含量较烤烟高103.36%,但氮素积累量,硝酸还原酶和谷氨酰胺合成酶活性,色素和总糖及还原糖含量,NH₄-N和可溶性蛋白质含量,基因GDHA_1、GS1、NIA1和NIA2表达水平均较烤烟低,氮还原同化能力弱。由相关性分析得出,烟叶硝酸盐含量与氮还原同化酶活性和两糖含量均呈现负相关,相关系数达极显著水平;可溶性蛋白质含量与氮还原同化酶活性和两糖含量均呈现正相关,相关系数达极显著水平。氮还原同化能力弱和能量物质供应不足是引起白肋烟硝酸盐积累的主要原因。      

三种类型烟叶五年贮藏过程中TSNAs及其前体物含量变化趋势分析

以调制后的2种烤烟、2种白肋烟以及1种晒烟为试验样品,在5年自然贮藏过程中,定期取样测定不同类型烟叶内TSNAs和其前体物生物碱、硝酸盐含量。研究表明,随贮藏时间增加,5种烟叶NNN、NNK、NAB、NAT和TSNAs总量均不断上升,经拟合符合二次曲线增长模型。白肋烟TSNAs的含量最高,贮藏过程中增加量最多,且以四川白肋烟NNN和TSNAs总量增加幅度最大,其次是晒烟,烤烟TSNAs含量最低,且在贮藏过程中增加幅度较小。TSNAs前体物生物碱及硝酸盐含量在贮藏过程中呈下降趋势,以晒烟的烟碱含量最高且下降幅度较大,以四川白肋烟降烟碱含量最高且下降幅度最大。硝酸盐含量在不同类型烟叶间差异大,白肋烟硝态氮平均含量3076.50μg/g,比烤烟的28.05μg/g高109.68倍。烟叶TSNAs含量与生物碱和硝酸盐相关性均较高,其中硝酸盐含量与贮藏后TSNAs含量的相关性比贮藏前更大,与TSNAs形成更为密切。      

叶面喷施丙三醇对烟叶碳氮代谢及硝酸盐积累的影响

  目的  探索丙三醇对白肋烟碳氮代谢及其硝酸盐积累的调控机理,建立新的白肋烟增效减害调控技术。  方法  以白肋烟品种TN90和TN86为材料,设置不同丙三醇浓度试验,并在确定丙三醇最佳适宜浓度的基础上,设置高氮和低氮两个处理,研究丙三醇对烟叶生物量积累、氮代谢关键酶活性、主要碳氮化合物含量及相关基因表达情况的影响。  结果  1）在高氮和低氮水平下,喷施丙三醇15 d后,烟叶生物量分别增加10.20%和13.36%,氮素积累量和氮素利用效率分别增加10.21%、3.15%、6.81%和3.11%,烟叶总糖和还原糖含量分别升高了25.15%、32.84%、47.76%和44.57%,但7 d后烟叶硝酸盐含量下降了53.22%和59.67%;2）低氮水平下喷施丙三醇烟叶色素、可溶性蛋白质和两糖含量与高氮条件下不喷施丙三醇结果相近;3）基因表达分析表明,喷施丙三醇显著促进了光反应途径、碳固定途径、蔗糖合成和氮代谢途径关键基因的表达,与对照相比,基因CP12-2、PPC16和NPF7.3的表达量增加0.5倍多。  结论  丙三醇能够提高烟叶碳氮代谢能力和氮素利用效率,提高烟叶碳水化合物含量和降低烟叶硝酸盐积累量,减氮配合喷施丙三醇是降低烟叶硝酸盐积累的有效途径。      

Relationship between nitrate/nitrite reductase activities in meat associated staphylococci and nitrosylmyoglobin formation in a cured meat model system

Quantitative determination of catalase, nitrate reductase, nitrite reductase and nitric oxide synthase activities (NOS) was performed on 11 different bacterial strains, mainly staphylococci, isolated from fermented sausages, bacon brine or cured meat products. All except one strain possessed catalase activity in the range from 1.0 to 6.1 μmol min^− 1 ml^− 1. Ten out of 11 bacteria strains showed nitrate reductase activity in the range between 50 and 796 nmol min^− 1 ml^− 1 and nine showed nitrite reductase activity in the range between 6 and 42 nmol min^− 1 ml^− 1. No evidence of NOS activity of the selected strains was detected. In a colour formation assay containing myoglobin all strains affected nitrosylmyoglobin (MbFe^IINO) formation in assays containing nitrite, whereas only strains having nitrate reductase activity generated MbFe^IINO in assays containing nitrate as the sole nitrosylating agent. The quantitative nitrate and nitrite reductase activity did not fully explain or correlate well with the observed rate of formation of MbFe^IINO, which seemed to be more affected by the growth rate of the different strains. The mechanism of the reduction of nitrite into NO of strains not having nitrite reductase activity remains to be fully elucidated, but could be due to a dual-mode action of nitrate reductase capable of acting on nitrate.     

一株墨鱼干源中度嗜盐菌的系统发育分析与生长特性

从市售墨鱼干表面分离纯化出一株中度嗜盐细菌NYJ01。16S rDNA序列测定和BLAST分析结果表明其16S rDNA与盐单胞菌属和栖盐田菌属中一些菌株的序列一致性高达99%。系统发育分析显示它与栖盐田菌属中4个种的模式菌株聚类在一个进化枝,表明菌株NYJ01是一种栖盐田菌。其耐盐范围是1%~20%NaCl,最适浓度为3%~10%NaCl;生长温度范围是10~45℃,最适温度为25~37℃;该菌在0.5%~15%的NaNO3培养液中生长良好,但不具有硝酸盐还原作用。可利用0.025%双乙酸钠、0.05%山梨酸钾、0.05%苯甲酸钠或0.05%脱氢乙酸钠等食品防腐剂抑制菌株NYJ01的生长。      

Influence of nitrate on microbial reduction of pertechnetate

Factors influencing microbial reduction of Tc(VII) in nitrate and radionuclide contaminated aquifer sediments were investigated using sediment microcosms containing organic electron donor, nitrate and Tc(VII). Microcosms underwent nitrate reduction followed by Tc(VII) reduction. During this transition, the microbial community changed from being dominated by bacteria affiliated with the genus Paenibacillus during the nitrate reduction phase, to those affiliated with genera Agrobacterium, Geothrix, and Desulfosporosinus during the Tc(VII) reduction phase. To investigate the mechanism of Tc(VII) reduction, the nitrate reducing strains Agrobacterium FRC-A2, Azoarcus FRC-B1, and a fermentative Clostridium FRC-C11 were isolated from sediment microcosms undergoing Tc(VII) reduction. Nitrate reducing bacteria reduced Tc(VII) effectively only in the presence of Fe(lll) and after nitrate was reduced, implying a major role for Fe(ll) as an electron shuttle in Tc(VII) reduction. It is likely that accumulation of nitrite blocks Fe(ll) production and hence Tc(VII) reduction during the active nitrate reduction phase. The pure culture of Clostridium FRC-C11 is able to reduce Tc(VII) enzymatically with H2 or glucose as electron donor and deposits insoluble Tc compounds within the cells in a manner that is not significantly influenced by the presence of nitrate. These results provided a possible mechanism for Tc(VII) reduction independent of Fe(III) and not influenced by nitrate.     

密闭气体环境对夏菠菜硝酸盐、亚硝酸盐及贮藏品质的影响

以菠菜为实验材料,研究低温贮藏条件下(4℃)密闭气体环境对菠菜贮藏品质,尤其对硝酸盐、亚硝酸盐及硝酸还原酶等酶活性的影响。结果表明:与对照(非密闭环境)相比,低温密闭气体环境可显著减缓菠菜可溶性固形物、VC、叶绿素等贮藏品质的下降,维持菠菜较高的硝酸还原酶(NR)活性和抗逆酶活性(SOD、POD、CAT),抑制丙二醛的产生,贮藏8d硝酸盐和亚硝酸盐分别为1318.44、0.42mg/kg,较对照分别降低了31.96%、26.19%,实验表明低温密闭气体环境有效降低了硝酸盐和亚硝酸盐的累积,提升了菠菜的安全贮运品质。