Structural purity of magnetite nanoparticles in magnetotactic bacteria

Magnetosome biomineralization and chain formation in magnetotactic bacteria are two processes that are highly controlled at the cellular level in order to form cellular magnetic dipoles. However, even if the magnetosome chains are well characterized, controversial results about the microstructure of magnetosomes were obtained and its possible influence in the formation of the magnetic dipole is to be specified. For the first time, the microstructure of intracellular magnetosomes was investigated using high-resolution synchrotron X-ray diffraction. Significant differences in the lattice parameter were found between intracellular magnetosomes from cultured magnetotactic bacteria and isolated ones. Through comparison with abiotic control materials of similar size, we show that this difference can be associated with different oxidation states and that the biogenic nanomagnetite is stoichiometric, i.e. structurally pure whereas isolated magnetosomes are slightly oxidized. The hierarchical structuring of the magnetosome chain thus starts with the formation of structurally pure magnetite nanoparticles that in turn might influence the magnetic property of the magnetosome chains.     

植物乳杆菌HG20对大鼠类风湿关节炎的改善作用

为了获得一株对类风湿性关节炎具有辅助治疗作用的乳酸菌新菌株,本研究采用形态学观察、API50 CHL糖发酵实验、16S rDNA和pheS基因序列比对,对一株分离自黄瓜表面的乳杆菌新菌株HG20进行鉴定。通过踝关节肿胀程度、血清炎症因子水平和类风湿相关指标,评价菌株HG20对Ⅱ-型胶原诱导的类风湿性关节炎模型大鼠的治疗作用。结果表明:HG20菌株被鉴定为植物乳杆菌(Lactobacillus plantarum)。动物实验结果显示,给药21 d后,HG20组大鼠踝关节肿胀周长由3.98 cm降低至1.31 cm(65.52%);足趾容积由6.61 mL降低至2.35 mL(61.28%)。与模型组比较,植物乳杆菌HG20可显著降低血清炎症因子IL-1β(38.26%)、TNF-α(52.58%)水平,提高抗炎因子IL-10表达(55.38%),减少C反应蛋白(CRP 12.89%)、免疫球蛋白IgG(46.07%)和IgM(34.29%)水平。综上所述,植物乳杆菌HG20通过降低炎症反应和调节自身免疫,对类风湿性关节炎具有辅助治疗作用,是一株有潜在应用前景的益生菌新菌株。     

婴幼儿辅食中细菌总数及蜡样芽孢杆菌污染情况分析

通过平板菌落计算法和最大近似值（MPN）法检测市售婴儿辅食中细菌总数和蜡样芽孢杆菌污染情况,并对MPN法得到的疑似蜡样芽胞杆菌进行基因间隔序列（ITS）插入性序列分析和形态鉴定。结果表明,101份样品中只有30份样品菌落总数达标,合格率仅为29.7%,部分超标产品的细菌总数达105CFU/g~106CFU/g。市售3种婴幼儿辅食-米粉、奶伴侣和面条中细菌总数及食源性致病菌蜡样芽孢杆菌检出情况不容乐观。     

Enhanced removal of 1,2-dichloroethane by anodophilic microbial consortia

1,2-Dichloroethane (1,2-DCA) is a well-known recalcitrant groundwater contaminant. New environment-friendly approaches for the removal of 1,2-DCA that does not bring about volatilization of the compound are required. In this study, different anodophilic consortia enriched in microbial fuel cells (MFCs) operated under airtight conditions were shown to effectively degrade 1,2-DCA (up to 102 mg per liter reactor volume per day), while concomitantly generating a current. An anodophilic consortium previously enriched with acetate as the electron donor changed its composition at the rate of 48% per week and increased its richness (Rr) 3-fold, upon adapting to 1,2-DCA as the new electron donor. After being stable, during 1 month of operation, it removed up to 95% of the 1,2-DCA amount in the medium in the first 2 weeks, while converting 43 ± 4% of electrons available from the removal to electricity. A natural consortium from a 1,2-DCA contaminated site changed its composition at the rate of 9% per week and increased its Rr 2-fold, upon adapting to the MFC anode conditions with 1,2-DCA as the electron donor. After being stable, during 1 month of operation, it removed up to 85% of the 1,2-DCA amount in the medium in the first 2 weeks and the coulombic efficiency was 25 ± 4%. The operation of the MFCs under closed circuit conditions resulted in higher 1,2-DCA removal rates than the operation under open circuit conditions, indicating that bioelectrochemical activities enhanced the removal of 1,2-DCA in the MFC anode. The production of ethylene glycol, acetate and carbon dioxide indicated that the anodophilic bacteria oxidatively metabolized 1,2-DCA, probably by means of a hydrolysis-based pathway. The results show that MFCs can be potentially used as a practically convenient technology for the biological removal of 1,2-DCA.     

A survey on the milk chemical and microbiological quality in dairy donkey farms located in NorthWestern Italy

There is a growing interest in donkey's milk as food for sensitive consumers, such as infants with cow's milk protein allergy and elderly people. The aim of this study was to carry out a survey on the dairy donkeys farming in Piedmont, Italy. The research was conducted in order to analyze the farm characteristics as well as the chemical and microbiological quality of milk. All the farms were small-sized, family-run, and, in most cases, animals were farmed semi-extensively. The donkey milk from Piedmont farms was characterized by a protein content around 1.5 g/100 mL and a fat content lower than 0.1 g/100 mL. Lysozyme activity was considerably higher than that reported in raw cow milk. The milk microbiological profile greatly differed among the farms. Milk sampled in the farm that performed hand milking showed total viable counts significantly lower than milk collected in the farms equipped with automatic milking. Samples were tested for several pathogens and negative results were observed, except for the detection of Bacillus cereus in one sample. The survey provided useful data for the laying down of recent regional regulation for the production and commercialization of donkey's milk. The results of the survey indicate that further research is needed in order to define the best management and nutritional strategies for the improvement of the quali-quantitative production of dairy donkeys.     

载体选择及细菌连续培养试验研究

对几种不同载体进行了选择,采用选定的载体聚氯乙烯屑进行了细菌固定化和细菌的快速培养试验,试验结果良好;并考察了温度对细菌氧化亚铁速率的影响,结果表明,温度对细菌活性影响很大,温度低于7℃,细菌活性很差,温度高于50℃,细菌丧失活性。为了保持细菌良好活性,最好保持菌液温度在30℃左右。     

Injury Mechanisms of Lactic Acid Bacteria Starter Cultures During Spray Drying: A Review

Lactic acid bacteria (LAB) starter cultures can be processed by many drying techniques, among which spray drying has great potential. However, injuries of LAB during spray drying lead to a low survival rate. The microbial injuries of LAB during spray drying are specifically induced by dehydration inactivation, thermal inactivation, and balance between the two. To reduce the drying temperature, new drying techniques based on spray drying were tried; that is, low-temperature vacuum–spray drying and spray–freeze drying.     

乳酸菌抗冷胁迫作用研究进展

极端低温会导致细胞内及周围形成冰晶,降低细胞膜的流动性和透过性,导致部分蛋白质及核酸的异常折叠,从而影响细胞的存活性能.本文综述了冷胁迫对乳酸菌细胞膜流动性、蛋白质和核酸功能造成的影响,总结了乳酸菌抗冷胁迫所采用的策略,并归纳了研究乳酸菌抗冷胁迫作用的常用方法.同时,对乳酸菌抗冷胁迫作用未来的研究方向进行展望,即可从基...     

余甘子圣女果复合饮料发酵工艺及对运动耐力的影响

以余甘子提取液和圣女果汁为原料,通过乳酸菌发酵制得具有抗疲劳作用的余甘子圣女果复合发酵饮料.基于单因素实验结果,采用响应面分析法优化该复合发酵饮料的制备工艺,同时利用动物实验考察其对小鼠运动耐力的影响.结果 表明,最佳发酵工艺为:乳酸菌接种量0.6％、余甘子提取液与圣女果汁的体积比1:3、发酵温度45℃、发酵时间29....     

马铃薯淀粉汁水混菌发酵条件优化及应用

为了提高马铃薯淀粉加工汁水中蛋白质的降解率及减少汁水发酵过程中臭味物质的产生,实现马铃薯淀粉汁水的绿色处理及资源化利用,在低温环境（15℃）下将好氧型苔藓假单胞菌和厌氧型黏质沙雷式菌进行混合发酵。采用单因素和响应面曲线法对发酵条件进行优化,结果显示当苔藓假单胞菌与黏质沙雷氏菌接种质量比为1.7∶2.0,接种体积分数为1.98%,发酵48h后,马铃薯淀粉汁水中蛋白质降解率为65.32%,氨氮质量浓度较未发酵组降低了51.05%,磷酸盐质量浓度提高了18.67%。同时,硫化氢、3-甲基吲哚等挥发性恶臭味物质未检出,尸胺、组胺、色胺、精胺等生物胺类物质未检出;此外,汁水发酵过程中吲哚乙酸-缬氨酸甲酯、氧化吲哚乙酸等植物生长激素质量浓度增加,此汁水稀释后可提高黄瓜种子的发芽率。此方法低成本地解决了马铃薯淀粉加工汁水在低温环境下处理排放的部分问题,为发酵汁水后续资源化利用提供了科学依据。