响应曲面法优化鼠李糖乳杆菌Ls-8菌株产抑真菌活性物质的条件

在使用Plackett-Burman设计试验的基础上,筛选出发酵时间、乳清粉、蔗糖和乙酸钠为鼠李糖乳杆菌Ls-8菌株发酵产抑真菌活性物质的4个关键影响因子。采用响应曲面法对这4个关键因子进行了优化,根据二次多项式回归方程求解得出,在发酵时间为82h、乳清粉添加量为29g/L、蔗糖添加量为25.5g/L、乙酸钠添加量为10.7g/L时、Ls-8发酵液的抑菌活性可达0.66AU/mL。     

啤酒污染乳酸菌PCR引物的设计与验证

根据细菌16SrDNA序列的特点,对啤酒中常见污染乳酸菌16SrDNA序列进行分析,设计合成了针对啤酒污染乳酸菌的特征引物。并用该引物对从啤酒厂分离到的7种乳酸菌进行了检测,PCR结果表明该引物能够准确检测到啤酒中常见的乳酸菌。     

东北酸菜发酵乳酸菌的筛选及评价

为获得适用东北酸菜发酵的乳酸菌菌株,该研究通过对来源于发酵蔬菜10株乳酸菌的生长性能和发酵特性进行评价,发现植物乳植杆菌YJ132和肠膜明串珠菌肠膜亚种UA107显示出显著的发酵潜力：培养16 h后,发酵液OD600 值分别升高至1.707和1.672,而pH值分别降低至3.93和3.88,培养24 h后,可滴定酸度（TA）含量为65.62 g/L和63.21 g/L,对亚硝酸盐的降解率达到96.41%和95.78%,在5% NaCl溶液中培养24 h后OD600 值仍达到1.51以上,综合评价菌株YJ132和UA107可作为发酵菌种用于东北酸菜发酵。利用YJ132和UA107制备酸菜,发酵末期酸菜样品中TA含量为35.96 g/L,还原糖和可溶性蛋白含量降低至6.51 mg/g和111.27 μg/g,并在发酵初期显著降低亚硝酸盐的含量,与对照组相比差异极显著（P<0.01）。接种乳酸菌可抑制有害菌肠杆菌的增殖（P<0.01）,增加酸菜中微生物群落的多样性,同时乳杆菌在发酵中后期始终是优势菌群,由此推断YJ132和UA107是通过调控微生物群落来提升东北酸菜的品质。综上所述,YJ132和UA107是适用于东北酸菜发酵的优良乳酸菌菌种。     

The effect of high pressure on the microbiological quality and other characteristics of cooked sausages packed in a modified atmosphere or vacuum

The aim of this study was to analyse the effect of high pressure (HP) on the shelf life and other selected characteristics of two types of cooked sausages, which were packed under vacuum or modified atmosphere. The total viable count in samples treated with 600 MPa/5 min decreased during 35 days of storage (4 ± 2 °C) to a maximum of 1.3 log CFU/g. Microbial counts of 4–5 log CFU/g were detected in control samples not subjected to HP. Instrumental colour analysis did not reveal any statistically significant differences between the meat products subjected to HP and the control samples during the course of the experiment. No statistically significant differences were found during the sensory evaluation when meat samples subjected to HP and control samples were assessed.     

NDC-4型脱氢催化剂低活性成因分析及再生研究

通过对低活性NDC-4型脱氢催化剂物性与组分的分析,研究了影响催化剂性能的因素及催化剂低活性的成因。在此基础上探讨了对低活性NDC-4型脱氢催化剂进行再生以提高其活性的方法。结合现有生产装置及工艺条件,确定了低活性NDC-4型脱氢催化剂的再生方案,并成功应用于工业生产。     

一种利用反相高效液相色谱法测定乳酸菌发酵液中苯乳酸的方法及其评价

为建立一种反相高效液相色谱法(Reversed phase high performance liquid chromatography,RP-HPLC)检测乳酸菌发酵液中苯乳酸含量的方法,系统考察了3种固定相、2种流动相有机相、5种水相及其比例对苯乳酸RP-HPLC检测的影响并对方法进行了评价。确定了以双封端C₁₈色谱柱(4.6 mm×250 mm,5 μm)为固定相,0.05%三氟乙酸(Trifluoroacetic acid,TFA)-乙腈,体积比75∶25,等度洗脱,流速1 mL/min,检测波长210 nm,柱温30 ℃。在0.2~5.0 mg/L内线性良好,r=0.9998,回收率99.88%~101.08%,检出限0.1400 mg/L,定量限0.4600 mg/L,1 d精密度和重复性相对标准偏差(Relative standard deviation,RSD)为0.30%和0.64%,30 d精密度和重复性RSD为0.59%和0.79%,30 d内苯乳酸标准储备液稳定性RSD为2.45%,乳酸菌发酵液中苯乳酸合成量为0.1400 mg/L时,其扩展不确定度为0.0046,95%的置信区间,包含因子k=2。选用短乳杆菌P3(Lactobacillus brevis)和植物乳杆菌(Lactobacillus plantarum)ATCC8014发酵液为检测对象,培养120 h苯乳酸合成量分别为77.58和62.60 mg/L。结果表明,在该方法下苯乳酸能够稳定出峰,检测效率高,检测成本低,操作简单,结果准确可靠,适合检测大批量样品,可为苯乳酸的相关研究提供理论依据。     

Survival of Lactic Acid Bacteria in Commercial Frozen Yogurt

Survival of constitutive lactic acid bacteria (LAB) was studied in 265 samples from three batches of commercial frozen yogurt stored at -23°C for one year. The total LAB in the three batches was > 10⁷CFU/g, and batch C was comprised exclusively of streptococci. Decreasing LAB counts in batches A and B were very slight. Experimental storage conditions resulted in the survival of LAB even after the 60 to 67 wk period.     

化验室的暖通空调设计

通过一个具体工程示例,介绍石油化工装置中化验室暖通空调专业通风设计方案及其特点。     

LaB6热阴极陶瓷材料的研究进展

简要介绍了目前LaB6材料的研究现状及其用途，综述了国内外LaB6陶瓷粉末、多晶体、单晶体的制备工艺，并展望了LaB6材料的发展前景。     

New anionic alkylaryl surfactants based on olefin sulfonic acids

A new family of anionic surfactants has been produced by the simultaneous sulfonation and alkylation of aromatic compounds using olefin sulfonic acid(s). This new process does not require the conventional alkylation unit and the strong acid catalysts, such as AlCl₃ or HF, normally used for alkylation. The resulting alkylaryl sulfonic acids differ from existing prodeucts by having the sulfonate group attached to the alkyl chain rather than the aromatic ring. This allows for further derivatization of the aromatic compounds by leaving more positions open on the ring. Aromatic compounds that lend themselves to the new process include benzene, toluene, xylene, alkylbenzenes, phenol, alkylphenols, alkoxylated phenols, alkoxylated alkylphenols, alkoxylated alkylphenol/formaldehyde resins, naphthalene, and alkylnaphthalenes. Any type of olefin that can be sulfonated can be used as the starting material. These include internal and α-olefins, linear and branched olefins, polyolefins, and vinylidenes. Mono- and disulfonated compounds, as well as geminitype surfactants, are easily prepared.