Inactivation kinetics of inoculated Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enterica on strawberries by chlorine dioxide gas

Inactivation kinetics of inoculated Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enterica on strawberries by chlorine dioxide gas at different concentrations (0.5, 1, 1.5, 3 and 5 mgl(-1)) for 10 min were studied. A cocktail of three strains of each targeted organism (100 microl) was spotted onto the surface of the strawberries (approximately 8-9 log ml(-1)) separately followed by air drying, and then treated with ClO(2) gas at 22 degrees C and 90-95% relative humidity. Approximately a 4.3-4.7 logCFU reduction per strawberry of all examined bacteria was achieved by treatment with 5 mgl(-1) ClO(2) for 10 min. The inactivation kinetics of E. coli O157:H7, L. monocytogenes and S. enterica were determined using first-order kinetic models to establish D-values and z-values. The D-values of E. coli, L. monocytogenes and S. enterica were 2.6+/-0.2, 2.3+/-0.2 and 2.7+/-0.7 min, respectively, at 5 mgl(-1) ClO(2). The z-values of E. coli, L. monocytogenes and S. enterica were 16.8+/-3.5, 15.8+/-3.5 and 23.3+/-3.3 mgl(-1), respectively. Furthermore, treatment with ClO(2) gas significantly (p < or = 0.05) reduced the initial microflora (mesophilic, psychrotrophic bacteria, yeasts and molds) on strawberries. Treatment with ClO(2) gas did not affect the color of strawberries and extended the shelf-life to 16 days compared to 8 days for the untreated control.     

高产α-半乳糖苷酶菌株的筛选鉴定及发酵培养基的优化

从紫花苜蓿草种植土壤中筛选得到一株产α-半乳糖苷酶的菌株A1-19,结合形态学特征及分子生物学对其鉴定,并优化其发酵培养基。结果表明,菌株A1-19被鉴定为黑曲霉（Aspergillus niger）。对基础发酵培养基中碳源、氮源、无机盐及诱导物进行单因素优化,结果显示,其最佳碳源为乳糖,氮源为牛肉膏,无机盐为MgSO4、Na2HPO4、MnCl2,诱导物为水苏糖。最佳培养基配方为乳糖15.0 g/L,牛肉膏10.0 g/L,MgSO4·7H2O 1.0 g/L,Na2HPO4 0.5 g/L,MnCl2 1.0 g/L,水苏糖0.8 g/L。在此优化的培养基下,菌株A1-19产α-半乳糖苷酶酶活力7.85 U/mL,是优化前发酵酶活力的6.77倍。     

重组大肠杆菌生产谷胱甘肽合成酶系的摇瓶发酵条件

研究了重组大肠杆菌E.coli Ⅱ-1 摇瓶发酵生产谷胱甘肽合成酶系的工艺条件,确定了E.coli Ⅱ-1 的最适产酶条件.最佳发酵培养基组成（g/L）为葡萄糖10, 蛋白胨5, 酵母膏2.5, K     

克鲁斯假丝酵母ZJB 09162产羰基还原酶的产酶条件

研究了克鲁斯假丝酵母Candida krusei ZJB 09162产羰基还原酶的条件,确定了最适的培养基组成和培养条件:葡萄糖50.0 g/L,酵母膏50.0 g/L,(NH4)2HPO4 2.5 g/L,KH2PO4 2.5 g/L,NaCl 1.0 g/L,培养基初始pH6.0,装液量12%,接种量4%。将此条件下发酵培养60 h的菌体用于(R)-1,3-丁二醇的不对称合成,产物对映体过量值99%,产率85%。     

特基拉芽孢杆菌来源β-1,3-1,4-葡聚糖酶重组菌发酵培养基的优化

为了提高重组大肠杆菌(Escherichia coli BL21DE3)(pET-28a(+)-bgl)发酵产β-1,3-1,4-葡聚糖酶的能力,研究了发酵培养基中各类碳源及氮源的影响,并通过响应面分析法优化培养基各组分的含量。结果表明,甘油为最适碳源,酵母粉及胰蛋白胨为氮源。优化的培养基组成是:yeast extract终浓度为20 g/L,胰蛋白胨12.5 g/L,甘油14.1 mL/L,KH2PO42.17 g/L,K2HPO42.74 g/L。三角瓶发酵产β-葡聚糖酶酶活(2 978.2 U/mL),与初始培养基(1 671.9 U/mL)相比,提高了1.78倍。研究结果表明,发酵培养基的优化对重组大肠杆菌发酵生产工业酶具有重要作用。     

不同类型发花砖茶特征香气成分研究

采用感官审评方法、固相微萃取/气相色谱-质谱联用技术、香气活性值(odor activity value,OAV)法结合化学计量学方法,分析茯砖茶、发花白茶砖及发花红茶砖特征香气成分。结果表明,从感官上,3种发花砖茶均有典型"菌花香",但茯砖茶菌花香中带木香,且略带泥土气,发花白茶砖菌花香中带清香,发花红茶砖菌花香中带花香、甜香。3种发花砖茶中共检测出75种挥发性成分,以醛类、醇类、酮类及碳氢化合物为主,其中27种挥发性成分为呈香物质。基于OAV值和偏最小二乘判别分析,鉴定了3种发花砖茶中15种特征香气成分。其中,茯砖茶以具有青气和木香属性的己醛、壬醛、(E,E)-2,4-壬二烯醛、(E,E)-2,4-庚二烯醛、2-正戊基呋喃、3,5-辛二烯-2-酮、甲基庚烯酮、β-紫罗兰酮和氧化芳樟醇Ⅰ为特征香气成分;发花白茶砖以具有清香属性的苯乙醛为特征香气成分;发花红茶砖以具有蘑菇香、泥土气属性的1-辛烯-3-醇,具有花香属性的樟醇、芳樟醇和水杨酸甲酯以及甜木香的雪松醇为特征香气成分。     

葡糖醋杆菌J2-1静态发酵生产细菌纤维素的培养基优化

为提高葡糖醋杆菌（Gluconacetobacter）J2-1发酵生产细菌纤维素的产量,采用静态发酵方式,利用单因素试验对发酵培养基的碳源、氮源、乙醇、有机酸及无机盐进行优化,并在此基础上选取葡萄糖、MgSO4·7H2O和酵母粉添加量进行正交试验优化。结果表明,发酵培养基最优组分为：葡萄糖80 g/L、酵母粉18 g/L、乙醇2%（V/V）、Na2HPO4·12H2O 3 g/L、乳酸2 g/L、MgSO4·7H2O 0.4 g/L。在此优化发酵培养基条件下,葡糖醋杆菌J2-1静态发酵生产细菌纤维素产量达到9.34 g/L,是优化前的1.89倍。     

氮源对L-色氨酸发酵的影响

以L-色氨酸生产菌E.coli TRTH为供试菌株,研究了氮源对L-色氨酸发酵的影响。利用30 L发酵罐进行分批补料发酵试验,确定了最佳有机氮源和无机氮源分别为酵母粉和硫酸铵,进一步确定酵母粉和硫酸铵的最佳用量为1 g/L和10 g/L,最后采用NaOH和氨水混合补料控制发酵液中NH4+浓度在120 mmol/L以下,发酵38 h,菌体生物量和L-色氨酸产量分别达到53.42 g/L和32.6 g/L,实现了大肠杆菌的高密度培养。     

In vitro and in vivo assessment of cytochrome P450-mediated herb–drug interaction of Ssang-hwa-tang

We have evaluated the herb–drug interaction potential of Ssang-hwa-tang (SHT) mediated by cytochrome P450 (CYP) inhibition/induction. Further, the effects of fermentation on the CYP-mediated herb–drug interaction potential were determined. SHT showed inhibitory activity toward CYP1A2, but not 2A6, 2B6, 2C9, 2C19, 2D6, 2E1, and 3A4 in human liver microsomes. The results of the enzyme kinetic study suggested that the SHT-induced CYP1A2 inhibition is mixed reversible inhibition. The hepatic CYP expression and activity in rats treated with SHT were examined. The expression/activity of CYP2E1 increased as a result of SHT extract treatment (P < 0.005 or P < 0.001, respectively), which raises the possibility that SHT may increase the toxicity of environmental toxicants through the elevation of CYP2E1-mediated metabolic activation. SHT fermentation using Lactobacillus fermentum or Lactobacillus gasseri resulted in attenuation of the SHT-induced CYP1A2 inhibition, but not CYP2E1 induction, suggesting that changes in the chemical composition of SHT through fermentation can affect the inhibition of CYP1A2 activity.     

Comparison of sterol composition between Tuber fermentation mycelia and natural fruiting bodies

Truffle, belonging to Tuber genera, is a nutritious and sterol-rich edible fungus, and sterol is a potential health beneficial compound. A comparison of Tuber sterol composition indicates that the total sterol contents in the fermentation mycelia (i.e., 10.5 mg g⁻¹) (n = 3) were approximately 3.2-5.6 times higher than that of the fruiting bodies (p < 0.05) with the addition of soybean flour into the basal fermentation media. Moreover, the phytosterol profile of fermentation mycelia could be significantly improved by adding soybean flour into the fermentation media. After the addition of soybean flour, stigmasterol and β-sitosterol appeared in the fermentation mycelia and the contents of total phytosterols (2279 μg g⁻¹) (n = 3), brassicasterol (943 μg g⁻¹) (n = 3), and campesterol (418 μg g⁻¹) (n = 3) were all increased significantly (p < 0.05). Moreover, the total contents of sterols and phytosterols in the fermentation mycelia cultured in the soybean media were much higher than those in the fruiting bodies (i.e., 1883-3240 and 479-1832 μg g⁻¹, respectively) (n = 3, p < 0.05). This work confirms the potentiality of Tuber fermentation mycelia as the alternative resource for its fruiting bodies from the viewpoint of sterols production.     

Ethanolic extracts of Antrodia cinnamomea mycelia fermented at varied times and scales have differential effects on hepatoma cells and normal primary hepatocytes

Mycelia of Antrodia cinnamomea (AC), an edible fungus native to Taiwan, were produced by submerged fermentation with various fermentation times in 250 mL, 5 and 500 L fermentors and were evaluated for the effect of fermentation products on the viabilities of Hep3B and HepG2 hepatoma cells and normal primary rat hepatocytes. The results showed that the ethanolic extracts of AC mycelia (from 250 mL fermentation for 8 wk and 5 and 500 L fermentations for 4 wk) possessed high antihepatoma activity. The IC(50) of ethanolic extract of AC mycelia fermented for 8 wk in a 250 mL fermentor against Hep3B and HepG2 cells were 82.9 and 54.2 microg/mL, respectively. Furthermore, the IC(50) for Hep3B and HepG2, treated with ethanolic extract of AC mycelia fermented for 4 wk in the 5 L fermentor were 48.7 and 3.8 microg/mL, respectively. Those treated with ethanolic extract of AC mycelia fermented for 4 wk in the 500 L fermentor were 36.9 and 3.1 microg/mL, respectively. No adverse effects of all samples on normal primary rat hepatocytes were observed.     

蜜环菌多糖生产培养基的研究

进行了蜜环菌深层发酵产胞外多糖的培养基的研究,研究结果表明：以豆粕粉作氮源时,菌丝得率最高,以麸皮作氮源时,多糖产量最高;红薯粉为蜜环菌菌丝生长和多糖产量的最适碳源,最适培养基配方为：红薯粉3%,葡萄糖1%,豆粕粉1.5%,KH2PO40.15%,机械搅拌对菌丝的生长和多糖的产生都不利;接种后当即上摇床比接种后静置一段时间再上摇床的菌丝干重及多糖含量都多;培养基中加1%的乙醇对菌丝的生长和多糖的产生都不利;600ml发酵试验中,发酵液多糖含量可达0.485mg/ml,菌丝干重可达20.8g/L。当发酵液pH降为5.0左右,颜色开始变为棕褐色,菌丝亮光由强变弱时,即可终止发酵。     

Comparison of Industrial Scale Ethanol Production from a Palmyrah‐Based Carbon Source by Commercial Yeast and a Mixed Culture from Palmyrah Toddy

Palmyrah (Borassus flabellifer) based products were used as an alternative carbon source for industrial scale ethanol production. The fermentation medium was enriched with spent wash obtained from a distillation column. The performance of a commercially available baker's yeast in the media was compared with a ‘palmyrah toddy mixed culture’ where the organisms were obtained from the sedimentation of palmyrah toddy. In a laboratory scale study, the ethanol produced from a palmyrah fruit pulp extract, diluted with distilled water, was 16.5 gL^?1 (36 h) and 13.0 gL^?1 (48 h) with ‘palmyrah toddy mixed culture’ and baker's yeast respectively. The ‘palmyrah toddy mixed culture’ performed better than the baker's yeast with palmyrah fruit pulp extract, diluted either with distilled water or spent wash. Among the different palmyrah based carbon sources, both cultures preferred molasses diluted with spent wash and both performed best in the medium containing the spent wash supplemented with sucrose. In a 5,000 L industrial scale fermentation of 20° Brix molasses supplemented with 10 gL^?1 ammonium sulphate, 72 gL^?1 and 65 gL^?1 ethanol was produced by the ‘palmyrah toddy mixed culture’ (72 h) and the baker's yeast (90 h) respectively. As the performance of the ‘palmyrah toddy mixed culture’ was better than that of the baker's yeast, the former was selected for the industrial scale studies of molasses fermentation media diluted with spent wash. In these studies the temperature reached 42°C by 36 h and resultant cell death was observed. However ethanol production was higher and more rapid in the molasses diluted with spent wash, rather than in the molasses diluted with tap water and supplemented with (NH₄)₂SO₄. Cell recycle operation obviated the interruption in fermentation caused by temperature induced cell death and increased rates and efficiency of ethanol production were observed.     

樟芝深层发酵多糖促进乳酸菌生长及增殖

目的 研究樟芝（Antrodia cinnamomea）深层发酵胞内多糖（Antrodia cinnamomea intracellular polysaccharide,AIPS）及胞外多糖（Antrodia cinnamomea extracellular polysaccharide, AEPS）对乳酸菌体外发酵生长及增殖的影响。方法 采用水提醇沉法和提取樟芝深层发酵AIPS及AIPS,采用96孔板法考察不同浓度AIPS及AEPS对4株乳酸菌生长或增殖的影响,采用平板菌落计数法考察AIPS及AEPS不同单糖组分对乳酸菌生长的影响。结果 AIPS对干酪乳杆菌LBC1-1菌株（LBC1-1）、植物乳杆菌LBP3-2菌株（LBP3-2）及鼠李糖乳杆菌LGG菌株（LGG）的生长均有明显促进作用,且主要表现为缩短迟滞期及增加最大生长量;AEPS对LBP3-2、LGG及鼠李糖乳杆菌LV-1菌株（LV-1）的生长有显著促进作用,且主要表现为提高最大生长速率及最大生长量;AIPS及AEPS促进乳酸菌生长不是因为提供了碳源营养物质,而是其中的某一种或几种多糖成分发挥了促进作用。结论 樟芝深层发酵多糖能显著促进乳酸生长和/或增殖,本研究为开发新型多功能益生元提供新思路及理论依据。     

培养基影响大肠杆菌产L-天冬酰胺酶的研究

研究培养基的成分及添加量对大肠杆菌产生抗癌药物-L-天冬酰胺酶的影响.通过对大肠杆菌培养基中碳源、氮源以及微量元素的讨论,得知该菌株以蔗糖为碳源,添加量为0.7%,以0.5%牛肉膏 1.0%蛋白胨为氮源,添加0.01%的硫酸亚铁为微量元素,所产L-天冬酰胺酶的比酶活达到352.54 U/g,相比基本培养基培养提高了31%.     

枯草芽孢杆菌C3产抗菌物质发酵培养基的优化

该文利用对黑曲霉孢子萌发有抑制作用的枯草芽孢杆菌C3,研究优化产抗菌物质的发酵培养基组分.在碳源、氮源、C/N单因素多水平试验结果的基础上,设计Na+、Mg2+、K+度3因素3水平L9(33)正交试验,研究无机盐离子对枯草芽孢杆菌产抗菌物质的影响.结果表明,碳源为1％葡萄糖,氮源为蛋白胨和酵母浸粉各1.5％,碳氮比为1∶3,NaCl为0.5％,KH2PO4为0.1％,MgSO4·7H2O为0.15％时,枯草芽孢杆菌产抗菌物质的抑菌效果明显,对霉菌孢子萌发的抑制率提高了118.64％.     

重组大肠杆菌产谷氨酰胺转氨酶培养基及发酵条件优化

对已构建好的表达谷氨酰胺转氨酶的大肠杆菌Rosetta DE3的摇瓶培养条件及发酵条件进行优化,所获优化培养基配方为葡萄糖4.0g/L,酵母膏3.0g/L,NH4Cl 4.0g/L,Na2HPO42.0g/L,K2HPO41.0g/L,MgSO4.7H2O 1.0g/L,NaCl 3.0g/L。得菌株发酵培养的最佳优化条件为装液量为25mL,接种量为5%,加IPTG浓度为0.6mmol/L,诱导时间为4h。     

大肠菌群一步发酵法检测的研究

本实验以美国食品与药品管理局(FDA)的初发酵培养基LST以及从国标(GB)乳糖胆盐初发酵培养基中优选出的A3培养基作大肠菌群检测的初发酵基础培养基。首先在LST和A3中分别添加几种不同浓度的革兰氏阳性菌抑制剂进行大肠菌群检测。结果表明,革兰氏阳性菌抑制剂对革兰氏阳性菌和大肠菌群均有抑制,不利于大肠菌群检出。然后,在A3培养基中分别添加大肠杆菌以及枯草杆菌等七种革兰氏阳性菌进行大肠菌群检测。在210支混合发酵管中,结果吻合率为92.42%,假阳性和假阴性分别为2.84%、4.74%。T检验法表明,在初发酵中,革兰氏阳性菌的存在对大肠菌群检测没有明显影响。接着,本实验又在A3培养基中分别添加产生假阳性的革兰氏阳性菌进行纯种发酵检测。在120支假阳性纯种发酵管中,均不会产生阳性反应。大量镜检实验也充分显示,发酵液中主要是革兰氏阴性菌。综上结果说明,A3培养基是一种适宜大肠菌群生长,抑制革兰氏阳性菌生长的初发酵基础培养基,能在短期内使发酵管产气的菌群基本就是大肠菌群。因此,在大肠菌群检测中只需进行一步发酵法检验。     

木聚糖酶产生菌的筛选

目的 从土壤中筛选木聚糖酶产量高的菌株,并研究其产酶的初步条件.方法 根据培养基上水解圈的大小和摇瓶培养后木聚糖酶的酶活性,筛选产酶量高的菌株.通过一系列单因素试验,研究影响产酶的碳源、氮源和无机盐.结果 筛选到1株产木聚糖酶的菌株,其产酶的较优碳源、氮源和无机盐为麸皮(30 g/L)、牛肉膏(10g/L)和磷酸氢二钾(1.0 g/L).结论 筛选到的菌株具有生产木聚糖酶的潜力.     

利用响应面分析法优化高山被孢霉M E - 1 生产花生四烯酸培养基成分研究

在利用高山被孢霉ME-1 生产花生四烯酸(ARA)过程中,采用响应面分析法,对摇瓶中的培养基成分进行优化。建立了两个标准的多项式模型：在长达6.5d 发酵过程中,当葡萄糖、酵母膏、KH2PO4 和NaNO3 浓度分别为90.16、12.50、3.80 和3.54g/L 时,生物量将到最大,约36.86g/L;当葡萄糖、酵母膏、KH2PO4 和NaNO3浓度分别为103.16、11.66、3.80 和3.43g/L 时,AA 产量将到最大,约9.65g/L。预测值通过实验得到了充分的证实,预测值和实验结果相关性很好。发酵罐实验结果表明,在高山被孢霉ME-1 大规模发酵生产过程中,对培养基进行优化,将同时引起生物量(发酵5d,约34.21 ± 1.01g/L)和AA 产量(发酵6d,约9.86 ± 0.45g/L)的增加。