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1.
泡菜中亚硝酸盐含量的测定是高中生物学教学中的选修实验,但师生在该实验中鲜少关注影响亚硝酸盐含量的因素。本研究以白菜、白萝卜、豇豆3种蔬菜为材料,分别添加不同浓度的食醋制作成泡菜,运用光电比色法每天测定亚硝酸盐含量到第10天。结果表明:初期亚硝酸盐含量随制作时间的延长不断增高,第3天达到峰值,然后下降,泡白菜、泡萝卜、泡豇豆中峰值分别为64.32 mg/kg、24.03 mg/kg、1.58 mg/kg;添加食醋后3种泡菜亚硝峰均呈现不同程度下降,其中泡白菜0.6%食醋组、泡萝卜0.9%食醋组、泡豇豆1.2%食醋组亚硝峰最低,分别为27.67 mg/kg、13.26 mg/kg、0.59 mg/kg。  相似文献   

2.
厌氧氨氧化菌富集培养物对羟胺的转化研究   总被引:1,自引:0,他引:1       下载免费PDF全文
【目的】羟胺是厌氧氨氧化的重要中间产物,本研究旨在探明厌氧氨氧化菌对羟胺的转化特性。【方法】采用厌氧氨氧化菌富集培养物,以羟胺和亚硝酸盐为基质进行分批培养试验,检测反应液中基质和产物的消涨情况。【结果】不接种厌氧氨氧化富集培养物时,羟胺和亚硝酸盐具有化学稳定性,彼此不发生化学反应;接种厌氧氨氧化富集培养物后,羟胺和亚硝酸盐发生化学反应;反应过程中有中间产物氨的产生和转化,最大氨氮积累浓度为0.338mmol/L;液相中总氮浓度从起始的4.694mmol/L降至结束时的0.812mmol/L,转化率为82.7%。羟胺和亚硝氮浓度均为2.5mmol/L时,羟胺最大比污泥转化速率为0.535mmol/(gVSS.h),是厌氧氨氧化反应体系中氨氮最大比污泥转化速率的1.81倍。将羟胺浓度提高至5.0mmol/L时,羟胺和亚硝氮转化速率分别提高26.7%和120.7%,最大氨氮积累浓度为0.795mmol/L;将亚硝氮浓度提高至5.0mmol/L时,羟胺和亚硝氮转化速率分别提高6.9%和9.0%,最大氨氮积累浓度为1.810mmol/L。【结论】厌氧氨氧化富集培养物能够转化羟胺,其对羟胺的转化速率高于对氨的转化速率。羟胺相对过量可显著加快羟胺和亚硝酸盐的转化速率,亚硝酸盐相对过量对羟胺和亚硝氮转化速率影响不大,提高羟胺或亚硝氮浓度均会增大中间产物氨氮的积累。实验现象可用van de Graaf模型解释,对于进一步开发厌氧氨氧化工艺具有重要的理论意义。  相似文献   

3.
乳酸菌混合生长降解亚硝酸盐能力的研究   总被引:2,自引:0,他引:2  
通过对植物乳杆菌和肠膜明串珠菌混合发酵降解亚硝酸盐能力的研究得出乳酸菌混菌发酵能显著降低发酵液中亚硝酸盐含量的结论.此外,研究还发现菌粉活化12 h后降解效果最佳.该研究为发酵蔬菜用乳酸菌发酵剂的开发及其产品安全性研究提供理论指导.  相似文献   

4.
亚硝酸盐影响Lactobacillus brevis 4903发酵的研究   总被引:1,自引:0,他引:1  
通过研究可知,亚硝酸盐对Lactobacillusbrevis4903发酵有抑制作用,环境中亚硝酸盐一旦分解掉,这种抑制作用就会被解除。分析其原因:①亚硝酸盐抑制了乳酸菌生长,从而抑制了乳酸发酵;②在发酵初期可能因亚硝酸盐还原酶的作用,使亚硝酸盐酶解生成NH3,NH3中和了乳酸菌生成的酸(H ),从而使环境pH值的下降和酸的积累变得缓慢。  相似文献   

5.
短乳杆菌有较强去除亚硝酸盐能力 ,亚硝酸盐含量在 2 5 0mg L以内 ,接种短乳杆菌48h亚硝酸盐全部去除。短乳杆菌处理亚硝酸盐主要处于亚硝酸还原酶还原亚硝酸盐阶段。短乳杆菌去除亚硝酸盐的最适pH值为 5.0~ 6.0 ,最适温度为 3 0℃ ;在其它条件不变的情况下 ,发酵初期 (1 0~ 2 6h)亚硝酸盐去除量随接种量的增加而增加 ,最适接种量为5 %。亚硝酸盐含量在 2 0 0mg L以内 ,短乳杆菌对亚硝酸盐的去除量与底物浓度有极显著的线性关系。  相似文献   

6.
【背景】烟草特有亚硝胺(tobacco-specific nitrosamines, TSNAs)是烟草于调制和发酵阶段产生的一类致癌物质,由烟草生物碱与氮氧化物发生亚硝化反应生成,生物碱和亚硝酸盐是TSNAs的直接前体物质。【目的】发掘适用雪茄高温发酵且显著降低TSNAs形成与积累的微生物。【方法】以TSNAs前体物质亚硝酸盐的高效降解为目标,对从雪茄烟叶分离得到的烟草源微生物菌株进行高温培养、亚硝酸盐降解及亚硝酸盐耐受能力研究,得到可于50℃高效降解亚硝酸盐及耐受高浓度亚硝酸盐的微生物菌株,将菌株应用于雪茄烟叶高温发酵35 d,对发酵前后亚硝酸盐、TSNAs、常规化学成分和中性香味成分含量进行测定,分析菌株在雪茄烟叶发酵中对TSNAs含量及烟叶品质的影响。【结果】获得了3株于50℃高效降解亚硝酸盐的菌株NY7、NY8和NY9,分别鉴定为莫海威芽孢杆菌(Bacillus mojavensis) NY7、耐盐芽孢杆菌(Bacillus halotolerans) NY8和枯草芽孢杆菌(Bacillus subtilis) NY9,其中B. halotolerans NY8亚硝酸盐降解能...  相似文献   

7.
2009年以沈阳市蔬菜生产示范基地为平台,研究不同轮作模式对消减设施菜地土壤氮、磷淋移和蔬菜硝酸盐、亚硝酸盐积累的作用.结果表明:经过一年的蔬菜种植后,设施菜地土壤pH呈下降趋势,下降了0.09~0.47单位;与本底相比,菜地土壤表层的全磷含量明显升高,速效磷含量(86.80~161.04 mg·kg-1)明显高于60 mg·kg-1的警戒指标,设施菜地土壤硝态氮(NO3--N)含量较高,并发生明显的淋移;除菠菜中亚硝酸盐含量超标外,3种轮作模式下的蔬菜硝酸盐和亚硝酸盐含量都符合国家无公害蔬菜安全标准;针对保护地土壤酸化、磷素累积和NO3--N淋移现状,应采取相应措施予以恢复;从3种轮作模式的结果看,在油菜一黄瓜-豇豆轮作模式下,土壤对pH的变化幅度最小,且土壤NO3--N的淋移现象较弱,氮、磷的回收率也较高,但在消减土壤磷淋移以及蔬菜硝酸盐和亚硝酸盐积累方面效果不明显.  相似文献   

8.
王艺雅  张其中 《微生物学通报》2019,46(10):2512-2528
【背景】中国是水产养殖大国,氨氮、亚硝态氮是水体中主要的氮源污染物。水体氨氮超标不仅会损伤水生动物的神经系统和肝肾系统,还会导致体表及内脏充血。亚硝态氮过高会阻碍血液运载氧气能力,导致鱼虾缺氧、免疫力下降,从而引发肠炎、烂鳃,甚至窒息死亡。部分光合细菌有去除水体氨氮、亚硝态氮的能力,且对环境友好无二次污染。【目的】从广东养殖水体分离、纯化、筛选出生物活性好的光合细菌(编号SP3)进行种属鉴定,优化培养条件,检测其去除水体氨氮和亚硝态氮的能力,为养殖水体去除氨氮和亚硝态氮提供目标菌株。【方法】用双层平板法从混合菌液中分离得到光合细菌,通过革兰氏染色、碳源利用试验、对无机电子供体的利用试验以及16SrRNA基因序列分析对目标菌株进行种属鉴定;测定菌株SP3在不同pH、不同浓度NaCl条件下的OD600,优化培养条件;通过测定7d内SP3菌株在不同浓度氨氮(氯化铵配制)和亚硝态氮(亚硝酸钠配制)中OD600的变化趋势,确定该菌株对不同氮源的利用情况;用纳氏比色法、分光光度法测定SP3菌株降解水体氨氮和亚硝态氮的能力。Genome walking扩增获得亚硝酸盐还原酶基因(nirS),通过荧光定量PCR研究nirS在氨氮、亚硝态氮去除过程中的表达动态。【结果】筛选出的菌株SP3为革兰氏阴性菌,短杆状;能以醋酸盐、丙酮酸盐、丙酸盐、丁酸盐、乳酸盐、富马酸盐、琥珀酸盐、苹果酸、果糖、葡萄糖作为碳源,不能以乙醇和丙酮作为碳源;能利用硫化钠、硫代硫酸钠、亚硫酸钠作为无机电子供体; 16SrRNA基因序列分析表明其与沙氏外硫红螺菌(Ectothiorhodospira shaposhnikovii)序列相似度为99%;菌株SP3适宜pH为6.0-8.5,适宜盐度为0-3%;菌株SP3以铵盐作为氮源时生长状态明显优于亚硝酸盐;以初始菌液浓度8.6×109CFU/mL、起始氨氮量84.15±0.58 mg/L的条件培养7 d,水体氨氮累计去除量为79.45±0.29 mg/L,氨氮累计去除率达到94.42%;在同样菌浓度和2mg/L亚硝酸钠的条件下培养5d,水体亚硝态氮含量低于检测限0.003mg/L。在菌株SP3去除氨氮、亚硝态氮过程中nirS相对表达量上调。【结论】菌株SP3为沙氏外硫红螺菌(E.shaposhnikovii),能有效去除水中氨氮和亚硝态氮,具有净化水质作用,在水产养殖和污水处理中有广阔应用前景。  相似文献   

9.
以甘肃浆水传统酿造工艺为依托,分析了浆水中亚硝酸盐、硝酸盐、硝酸还原酶、p H、还原糖和总酸等理化指标的动态变化,以及乳酸菌菌群的变化规律,并探讨了乳酸菌对亚硝酸盐的降解作用。结果表明:该浆水产品发酵72 h后亚硝酸盐含量为2.76 mg/kg,低于国家标准(GB 2714-2003)规定的亚硝酸盐要求;明确了浆水发酵过程中还原糖、p H、总酸及乳酸菌总数的变化规律;证明了乳酸菌在浆水发酵过程中可以降低亚硝酸盐的含量。  相似文献   

10.
短乳杆菌(Lactobacillus brevis)去除亚硝酸盐的研究   总被引:8,自引:0,他引:8  
短乳杆菌有较强去除亚硝酸盐能力,亚硝酸盐含量在250mg/L以内,接种短乳杆菌48h亚硝酸盐全部去除。短乳杆菌处理亚硝酸盐主要处于亚硝酸还原酶还原亚硝酸盐阶段。短乳杆菌去除亚硝酸盐的最适pH值为5.0~6.0,最适温度为30℃;在其它条件不变的情况下,发酵初期(10~26h)亚硝酸盐去除量随接种量的增加而增加,最适接种量为5%。亚硝酸盐含量在200mg/L以内,短乳杆菌对亚硝酸盐的去除量与底物浓度有极显著的线性关系。  相似文献   

11.
以市售苦瓜为原料,研究了减压处理对泡菜自然发酵过程中乳酸菌的数量、总酸、乳酸、多糖及亚硝酸盐含量影响的变化规律。研究表明:减压处理可以促进泡菜发酵过程乳酸菌的增殖及乳酸含量的快速积累,并可以有效地降低泡菜中亚硝酸盐的含量,对泡菜多糖的保留有一定的作用。在0.04MPa(真空度)下,发酵终止时,乳酸菌活菌数仍可达到4.1×10~7个/mL,此时泡菜中的总酸含量为24.79mg/mL,其中乳酸含量为2.33%。  相似文献   

12.
芜湖市几种常见蔬菜中亚硝酸盐含量分析   总被引:9,自引:0,他引:9       下载免费PDF全文
1 引  言近年来,蔬菜中硝酸盐、亚硝酸盐污染情况已经越来越受到人们的关注.现已证实,人体摄入的硝酸盐有80%以上来自蔬菜[21,22,29],硝酸盐可被硝酸还原细菌还原为亚硝酸盐,亚硝酸盐在人体内积累到一定程度时,会引起人体血液缺氧中毒反应.若亚硝酸与次级胺结合可形成强致癌  相似文献   

13.
The aim of this study was to investigate the effect of inoculated fermentation on the quality of Chinese sauerkraut. To this end we studied a co-culture system consisting of Lactobacillus plantarum Shanghai brewing 1.08 and Zygosaccharomyces rouxii CGMCC 3791 during inoculated sauerkraut fermentation. The nitrite concentrations in pickled cabbage and radish inoculated with starter cultures of L. plantarum and Z. rouxii were significantly lower than those in the spontaneous fermentation system during the whole fermentation process. In addition, co-culture of L. plantarum and Z. rouxii during the production of sauerkraut decreased the formation of biogenic amines in the pickled vegetables. Using gas chromatography–mass spectrometry we also compared the levels of volatile compounds in inoculated and naturally fermented Chinese sauerkraut. Sixty compounds were identified, with the sauerkraut inoculated with starter cultures containing overall higher contents of volatile compounds, including acids, alcohols, esters, and phenols. The structure of the microbial community during the production of sauerkraut was studied using phospholipid fatty-acid (PLFA) analysis. This analysis revealed that the brine of inoculated sauerkraut contained significantly higher contents of Gram-positive and fungal PLFAs and a lower content of Gram-negative PLFAs, suggesting that the improved quality of inoculated Chinese sauerkraut may be ascribed to the inhibition of the growth of Gram-positive during sauerkraut fermentation. These results may indicate a new strategy to enhance the quality of Chinese sauerkraut.  相似文献   

14.
重庆市蔬菜硝酸盐、亚硝酸盐含量及其与环境的关系   总被引:71,自引:0,他引:71  
黄建国  袁玲 《生态学报》1996,16(4):383-388
在重庆市的主要蔬菜中,硝酸盐含量依次为根菜类>叶菜类>葱蒜类>瓜类>豆类>茄果类,前3类的硝酸盐含量超标,但各种蔬菜的亚硝酸盐含量一般较低,未超过卫生标准。就同一种蔬菜的不同样品而言,硝酸盐和亚硝酸盐含量的差异很大,说明品种或环境条件可显著影响其含量。重庆市多雾少光,冬春低温,土壤含氮量和钠高子含量较高,有效钾含量较低可能是导致蔬菜大量积累硝酸盐的环境因素。蔬菜不同器官硝酸盐和亚硝酸盐含量各异,根>茎>叶柄>叶片。  相似文献   

15.
Ye RW  Tao W  Bedzyk L  Young T  Chen M  Li L 《Journal of bacteriology》2000,182(16):4458-4465
Bacillus subtilis can grow under anaerobic conditions, either with nitrate or nitrite as the electron acceptor or by fermentation. A DNA microarray containing 4,020 genes from this organism was constructed to explore anaerobic gene expression patterns on a genomic scale. When mRNA levels of aerobic and anaerobic cultures during exponential growth were compared, several hundred genes were observed to be induced or repressed under anaerobic conditions. These genes are involved in a variety of cell functions, including carbon metabolism, electron transport, iron uptake, antibiotic production, and stress response. Among the highly induced genes are not only those responsible for nitrate respiration and fermentation but also those of unknown function. Certain groups of genes were specifically regulated during anaerobic growth on nitrite, while others were primarily affected during fermentative growth, indicating a complex regulatory circuitry of anaerobic metabolism.  相似文献   

16.
17.
Summary Alcoholic fermentation cycle with Saccharomyces cerevisiae has been studied on beet molasses exempt from nitrite ions and containing added amounts of these ions from 200 to 400 ppm. Experimental results indicate that fermentation duration increases with increasing nitrite concentration in the molasses. A detailed kinetic study reveals that this increase occurs only during the latency period. Moreover, the biomass and the ethanol production curves drawn after this period appear to be quite linear, their slope being independent of initial nitrite concentration. It has also been shown that nitrite ions turn completely into nitrate ions during the latency period. We have proved that this oxidation must be ascribed to yeast action and not to any chemical reactions between nitrite ions and molasses components.  相似文献   

18.
Under anaerobic conditions, Propionibacterium pentosaceum reduces nitrate to nitrite until nitrate is exhausted from the medium when nitrite is converted into N2 or N2O. In the presence of nitrate, fermentation patterns for lactate, glycerol and pyruvate were different from those obtained during anaerobic growth without an inorganic electron acceptor. In the presence of these substrates, a drastic decrease in propionate formation was observed, some pyruvate accumulated during growth with lactate, and acetate was produced from glycerol. Acetate production from lactate and pyruvate was not influenced by the presence of nitrate. Furthermore, CO2 was produced by citric acid cycle activity. The fermentation pattern during nitrite reduction resembled that of P. pentosaceum grown anaerobically without an inorganic electron acceptor. Nitrits has a toxic effect, since bacteria inoculated into a medium with 9 mM-nitrite failed to grow. The cytochrome spectrum of anaerobically grown P. pentosaceum was similar with and without nitrate. In membrane fractions of bacteria grown anaerobically with nitrate, cytochrome b functioned in the transfer of electrons from lactate, glycerol I-phosphate and NADH to nitrate. Molar growth yeilds were increased in the presence of nitrate, indicating an increased production of ATP. This could be explained by citric acid cycle activity, and by ocidative phosphorylation coupled to nitrate reduction. Assuming that I mol ATP is formed in the electron transfer from lactate or glycerol I-phosphate to nitrate, and that 2 mol ATP are formed in the electron transfer from NADH to nitrate, YATP values (g dry wt bacteria/mol ATP) were obtained of between 5-0 and 12-6. The higher YATP values were similar to those obtained during anaerobic growth without an inorganic electron acceptor. This supports the assumptions about the efficiency of oxidative phosphorylation for electron transport to nitrate. Low YAPT values were found when high concentrations of nitrite (15 to 50 mM) accumulated, and were probably due to the toxic effect of nitrite.  相似文献   

19.
Dissimilatory ammonification was indicated as the common feature of ten rhizobial strains representing six species and three genera. In the absence of external electron acceptors, all investigated strains were capable of ethanolic fermentation. However, induction of anaerobic nitrite reduction was shown to be coupled with a shift of fermentation towards acetate in all the strains tested. Three metabolic groups could be distinguished with regard to nitrite regulation of ethanolic fermentation. It was shown for Bradyrhizobium sp. strain USDA 3045 that nitrite is the signal for switching between fermentative pathways although both ammonia and acetate excretion could not accelerate until nitrate had been utilized first. In the absence of N oxyanions, ethanol was indicated as the main product of mannitol fermentation, five-fold more abundant than acetate. An inverse composition was found in nitrite-amended cultures, due to a four-fold increase in acetate excretion whereas ethanol was kept at low level. Nitrite-supported fermentation towards acetate has not been previously reported for rhizobia. This benefit of this pathway was a two-fold shorter doubling time on 1% mannitol and 2.5 mM nitrite compared to no-nitrite media variants but also enabled fermentation of the more reduced carbon compound glycerol.  相似文献   

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