响应面法优化深黄被孢霉产油突变株的发酵培养基配方北大核心CSCD

为了优化深黄被孢霉突变株的发酵培养基,在单因素实验基础上,采用响应面法(RSM)对深黄被孢霉产油突变株发酵培养基配方进行优化。结果表明,深黄被孢霉产油突变株最佳发酵培养基配方为:葡萄糖90.29 g/L,酵母膏4.14 g/L,Mg SO40.96 g/L,KH2PO41.99 g/L,p H 6.0。在最佳条件下油脂产量为12.01 g/L,比优化前(6.22 g/L)提高了93.09%。     

响应面法优化深黄被孢霉产油突变株的发酵培养基配方

为了优化深黄被孢霉突变株的发酵培养基,在单因素实验基础上,采用响应面法(RSM)对深黄被孢霉产油突变株发酵培养基配方进行优化。结果表明,深黄被孢霉产油突变株最佳发酵培养基配方为:葡萄糖90.29 g/L,酵母膏4.14 g/L,Mg SO40.96 g/L,KH2PO41.99 g/L,p H 6.0。在最佳条件下油脂产量为12.01 g/L,比优化前(6.22 g/L)提高了93.09%。     

L-精氨酸产生菌发酵培养基及发酵条件优化的初步研究

本文以钝齿棒杆菌诱变菌为实验菌株,采用摇瓶发酵的方式,研究了培养基组分(碳源、有机氮源、无机氮源及无机盐离子)与发酵培养条件(温度、接种量、初始p H及发酵液体积)对菌种产L-精氨酸的产量的影响。结果表明,该菌产L-精氨酸发酵培养基的最佳组分为:葡萄糖12%、硫酸铵4.5%、玉米浆2.5%、KH2PO40.005%、Mg SO4·7H2O0.01%、Fe Cl3·6H2O 0.01%、Mn SO4·H2O 0.05%及碳酸钙3%;最佳发酵条件是:培养温度为30℃、接种量为10%、初始p H为7.0及装液量为15m L/250m L。该菌以最优结果发酵,L-精氨酸的产量较基本培养基提高27.7%,达到了11.23g/L。     

复合菌固态发酵猪骨素产谷氨酸发酵条件优化

优化米曲霉-红曲霉复合菌固态发酵猪骨素产谷氨酸的发酵条件以提高谷氨酸产量。通过单因素实验和正交实验,以谷氨酸产量为指标,研究发酵时间、发酵温度、培养基初始p H和培养基含水量对谷氨酸产量的影响并对其进行优化。结果表明,培养基初始p H为6,培养基含水量为30%,发酵温度32℃,发酵5 d谷氨酸产量达到194.2 g/kg,总氨基酸产量达到768.5 g/kg,比优化前分别提高了15.7%和5.5%。     

基于代谢调控深黄被孢霉产γ-亚麻酸培养基优化

研究深黄被孢霉产γ-亚麻酸过程的代谢调控,从中得出对深黄被孢霉产γ-亚麻酸有促进作用的营养成分,并利用Plackett-Burman实验对培养基营养成分进行筛选。得出葡萄糖、KNO3、乙酸钠、柠檬酸钠为影响产油量的关键因素。在此基础上,以γ-亚麻酸产量为响应值,采用响应面法优化,确定4个关键因素的最佳水平。综合Plackett-Burman实验和响应面法确定的最佳培养基配方为:葡萄糖100.90 g/L、KNO31.57 g/L、乙酸钠3.42 g/L、柠檬酸钠4.56 g/L、酵母膏3.75g/L、KH2PO42.25 g/L、Mg SO4·7H2O 0.60 g/L、Ca Cl20.30 g/L、Fe SO40.15 g/L、Zn SO40.20 g/L。在最佳条件下γ-亚麻酸的产量达1 525.20 mg/L,比初始产量725.90 mg/L提高了1.1倍。     

刺孢小克银汉霉发酵产γ-亚麻酸时补料工艺研究

研究刺孢小克银汉霉(Cunninghamellaechinulata)发酵生产γ-亚麻酸(GLA)的补料工艺。结果表明,该菌株在含有0.25%黄豆饼粉的发酵培养基中,以分批补料方式,即培养2.5d后补入20g/L食用糖与10g/L麦芽糖混合液,培养第3d时补入1.0g/L(NH4)2SO4,在培养第4d补入2.0g/LMgSO4,在培养第5d补入2.0g/LMnSO4。培养10d,菌体生物量达17.065g/L,油脂产量达6.530g/L,GLA%达23.5157%,GLA含量达1535.58mg/L,与补料前相比,生物量、油脂量、GLA%、GLA含量分别提高79.67%、217.30%、14.85%和264.43%。     

丛梗孢酵母产赤藓糖醇的诱变选育

利用微波-硫酸二乙酯复合诱变对产赤藓糖醇丛梗孢酵母E54进行处理,以高渗平板和摇瓶发酵为筛选方法,得到遗传稳定的诱变高产株EW29;再采用氮离子注入对EW29进行诱变处理,摇瓶发酵筛选得到诱变株EN59,其90h发酵液中赤藓糖醇产量达到55.13g/L,较EW29提高20.3%,较E54提高36.9%,遗传稳定性较好。对突变株EN59的发酵培养基进行了优化,在优化培养基葡萄糖250g/L、酵母膏5g/L、KH2PO4 0.3g/L、MnSO4 ·4H2O 0.04g/L、CuSO4 ·5H2O 0.03g/L,初始pH4的条件下,90h发酵液中赤藓糖醇平均产量达到69.00g/L以上。在优化培养基的基础上进行5L罐发酵放大实验,发酵126h赤藓糖醇产量达到71.14g/L。     

枯草芽孢杆菌B26生产多隔镰孢霉抑制物工艺优化

采用正交试验设计对枯草芽孢杆菌B26 抑制多隔镰孢霉培养基配方及用量进行优化,单因素试验对B26产生活性物质的发酵条件进行选择。以多隔镰孢霉的抑制率为指标,B26 产生拮抗效果最好的发酵培养基配方用量是：蛋白胨25g/L、淀粉45g/L 、氯化钠1.5g/L、硫酸铵1.0g/L、磷酸氢二钾1.5g/L。产生活性物质的最优发酵条件为：种子菌龄24h、接种量5%、初始pH7、装液量20%、吐温-80 用量0.5%、发酵温度30℃、转速150r/min、发酵时间60h,获得B26 菌株发酵液对多镰孢霉的抑制直径为26mm,优于其他条件培养获得的拮抗效果。     

埃博霉素B高产菌株的选育及发酵工艺优化

以纤维堆囊菌(Sorangium cellulosum)So F5-76为诱变出发菌株,经紫外(UV)和亚硝基胍(NTG)复合诱变和筛选,获得一株高产突变菌株So F5-H23,其发酵产埃博霉素B的量可达79.83 mg/L,比出发菌株提高了1.27倍。通过Plackett-Burman实验和响应面分析法对纤维堆囊菌产埃博霉素B的发酵工艺进行优化。得到最佳发酵工艺为:马铃薯淀粉4.8 g/L,葡萄糖0.5 g/L,脱脂奶粉2.3 g/L,豆饼粉2 g/L,七水硫酸镁2 g/L,无水氯化钙2 g/L,EDTA-Fe3+2 m L/L,微量元素(TE)0.5 m L/L,吸附树脂2%,培养基初始p H 7.4,装液量50 m L,接种体积分数8%,温度30℃。在此最优条件下埃博霉素B产量为108.67 mg/L,比优化前提高了36.13%,此产量是国内外报道的埃博霉素最高产量。     

高山被孢霉突变株产花生四烯酸培养条件的研究

为了研究高山被孢霉突变株12-2-2产花生四烯酸(ARA)的培养条件,选取温度、p H、摇床转速和培养时间为4个影响因素,以生物量、油脂产量和ARA产量为综合评价指标,进行单因素实验和正交实验。结果表明,影响高山被孢霉突变株12-2-2产ARA的因素主次顺序为:温度﹥培养时间﹥摇床转速﹥p H;最优培养条件为:温度26℃,培养时间7 d,摇床转速160 r/min,p H 8。在最优培养条件下,高山被孢霉突变株12-2-2的生物量为32.31 g/L,油脂产量为12.98 g/L,ARA产量为5.12 g/L。     

Efficient production of a heterologous peroxidase, DyP from Geotrichum candidum Dec 1, on solid-state culture of Aspergillus oryzae RD005

The productivity of a peroxidase (DyP) originating from Geotrichum candidum Dec 1 was enhanced in the solid-state culture using Aspergillus oryzae RD005. When the humidity, water content, and temperature were adjusted to 60%, 50% and 27°C, respectively, the productivity of DyP reached 5.3 g per kilogram wheat bran, which was used as the solid medium. The yield of 5.3 g per kg wheat bran corresponded to the yield of a 56 kg submerged culture. The productivity per gram carbon of the medium in the solid-state culture was 4.1-fold that in the submerged culture.     

植物乳杆菌发酵桑葚酵素工艺优化及质量评价

目的:解决新鲜桑葚难以保存的问题，将新鲜桑葚制成桑葚酵素。方法:以新鲜桑葚汁为原料，植物乳杆菌为生产菌种，总酚含量为评价指标，通过单因素试验结合响应面试验优化了植物乳杆菌桑葚酵素的发酵工艺，并对桑葚酵素的理化、微生物及感官质量指标进行评价。结果:优化后发酵工艺条件为发酵时间40 h、发酵温度32℃、接种量25%,所制得的植物乳杆菌桑葚酵素的总酚含量达(43.48±0.67)μg/mL,是未经发酵的桑葚汁的1.62倍，可溶性固体物含量为5.36%,pH值为4.08±0.01,微生物指标满足国家标准；桑葚酵素呈紫红、色泽均匀，具有浓郁的桑葚果香和发酵的香味、无异味，酸味柔和、风味好，有光泽、无杂质及沉淀。结论:经植物乳杆菌发酵制得桑葚酵素的过程有生物活性物质产生，有利于提高桑葚酵素质量。     

鸡源大肠埃希氏菌mcr-1基因携带及分析

目的 了解在农业农村部禁止使用多黏菌素作为动物促生长使用后四川部分地区鸡源大肠埃希氏菌（E.coli）mcr-1基因的携带情况,为制定进一步防控措施提供依据。方法 采集四川部分地区市场售卖点肉鸡直肠拭子,用含有多黏菌素（终浓度4 μg/mL）的EC肉汤增菌接种含多黏菌素（终浓度4 μg/mL）的麦康凯平板,挑取可疑菌落,采用PCR方法鉴定菌株并检测mcr-1基因;微量肉汤稀释法测定mcr-1基因阳性菌株对临床常见抗菌药物耐药情况。脉冲场凝胶电泳（PFGE）对mcr-1基因阳性菌株进行同源分析。耐药基因质粒结合实验验证mcr-1基因传播途径。结果 从70份肉鸡样本中的13份检出mcr-1基因阳性大肠埃希氏菌,检出率18.57%（13/70）,对实验的13种抗生素,除13株mcr-1阳性菌株对头孢西丁有12株敏感以外,对其他抗生素都表现出不同程度的耐药,其中四环素和甲氧苄啶/磺胺甲恶唑耐药率最高,达到了100%（13/13）;其次是氨苄西林和氯霉素,耐药率为84.62%（11/13）。PFGE显示13株mcr-1阳性大肠埃希氏菌分属13个不同的型别;质粒结合实验显示mcr-1基因能够通过质粒传播。结论 mcr-1基因在鸡大肠内大肠杆菌中检测率比较高,且鸡大肠中mcr-1阳性大肠埃希氏菌的耐药情况比较严重。     

Influence of hyaluronidase addition on the production of hyaluronic acid by batch culture of Streptococcus zooepidemicus

Enhancement of hyaluronic acid (HA) production by Streptococcus zooepidemicus through increasing oxygen transfer rate via degradation of HA by hyaluronidase was investigated. Dissolved oxygen (DO) level became a limiting factor for HA production during 8–16 h, and thus hyaluronidase (0.05, 0.10, 0.15, 0.20, 0.25 g/l) was added at 8 h to degrade HA. Oxygen transfer rate coefficient and DO level during 8–16 h increased with increased hyaluronidase concentration. Compared to 5.0 ± 0.1 g/l of the control without hyaluronidase addition, HA production was increased from 5.0 ± 0.1 g/l to 6.0 ± 0.1 g/l when hyaluronidase concentration was 0.15 g/l. Further increase of hyaluronidase concentration had no effect on HA production. The molecular weight of HA decreased with the increased hyaluronidase concentration and decreased to 21 kDa when hyaluronidase concentration was 0.25 g/l from 1300 kDa of the control. The prepared low molecular weight HA (LMW-HA) could function as potential anti-angiogenic substances, antiviral and anti-tumor agents to possibly be used as functional food ingredients.     

The influence of precultivation parameters on the catabolism of branched-chain amino acids by Staphylococcus xylosus and Staphylococcus carnosus

The influence of precultivation parameters on the ability of Staphylococcus xylosus and Staphylococcus carnosus to convert branched-chain amino acids—leucine, isoleucine and valine—into volatile flavour compounds was investigated using resting cells in a defined reaction medium. The studied precultivation parameters were: growth phase, temperature, NaCl concentration and the concentration of leucine, isoleucine and valine (only for S. xylosus). Flavour compounds were sampled by automatic static headspace collection and separated/quantified using gas chromatography/flame ionization detection (GC/FID).Main catabolic products from degradation of leucine, isoleucine and valine were the flavour intensive branched-chain acids: 2- and 3-methylbutanoic and 2-methylpropanoic acids. The precultivation parameters altered the production of the branched-chain acids significantly, but to various degrees for S. xylosus and S. carnosus.Production of branched-chain acids by S. carnosus was only influenced slightly by the growth phase and not by changing the NaCl concentration between 4.0% and 10.0% (w/w). Lowering the temperature from 28°C to 18°C significantly decreased S. carnosus’ generation of branched-chain acids. In contrast, S. xylosus was significantly influenced by all precultivation parameters, in particular by the growth phase. Cells taken from growing cultures had a much higher production of branched-chain acids compared to cells taken from stationary cultures. Addition of leucine and valine to the precultivation medium enhanced the production of branched-chain acids whereas addition of isoleucine had the opposite effect.     

Effect of Zataria multiflora Boiss. essential oil and nisin on Salmonella typhimurium and Staphylococcus aureus in a food model system and on the bacterial cell membranes

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO: 0, 5, 15 and 30 μl 100 ml⁻¹) and nisin (N: 0, 0.25 and 0.5 μg ml⁻¹), temperatures (T: 25 and 8 °C), and storage times (up to 21 days) on growth of Salmonella typhimurium and Staphylococcus aureus in a commercial barley soup were evaluated in a factorial design study. The growth of S. typhimurium was significantly (P < 0.05) decreased by EO concentrations and their combinations with N concentrations at 8 °C. For S. aureus, the viable count was significantly (P < 0.05) inhibited by EO and N concentrations and their combinations, incubated at both storage temperatures. The mechanism of the antimicrobial action of EO, N, and their combinations against cell membranes of the tested organisms were also studied by measurement of the release of cell constituents and by the electronic microscopy observations of the cells. The significant increase of the cell constituents’ release of both organisms was observed as a result of treatments with EO and EO in combination with N. Electronic microscopy observations revealed that the cell membranes of S. typhimurium treated by EO and EO in combination with N were significantly damaged, while cells treated with only N looked similar to untreated cells. The electron micrographs of treated cells of S. aureus with EO, N, and their combination also showed important morphological damages and disrupted membranes.     

柠檬明串珠菌KM20中D-乳酸脱氢酶的特性

目的：分析柠檬明串珠菌中D-乳酸脱氢酶（D-LDH）的酶学特性。方法：对柠檬明串珠菌KM20中D-乳酸脱氢酶基因进行克隆表达并构建表达质粒,转化至Escherichia coli BL21（DE3）中实现过表达。结果：经Ni-NTA柱亲和层析纯化后,D-LDH-1与D-LDH-2编码的蛋白分子质量分别为40.0,38.5 kDa;比活力分别为2.18,153.10 U/mg;在丙酮酸还原中两种酶的最适pH值与最适温度均为8.0与40 ℃;而乳酸氧化时D-LDH-2的最适pH值与最适温度分别为12.0与30 ℃。D-LDH-1与D-LDH-2对草酰乙酸、苯丙酮酸和2-酮戊二酸具有较强的催化能力,且Ca²⁺、Cu²⁺和Na⁺对其酶活性均具有促进作用,Zn²⁺与SDS对酶活性有极高的抑制作用。此外,两种酶对丙酮酸的K_m值分别为2.98,6.11 mmol/L,对丙酮酸的K_cat/K_m分别为6.04×10²,2.28×10⁴ L/（mol·s）,LDH-2对D-乳酸的K_cat/K_m为65.0 L/（mol·s）。结论：D-LDH-1与D-LDH-2为柠檬酸明串珠菌中催化D-乳酸合成的关键酶。     

Effect of X-ray treatments on inoculated Escherichia coli O157: H7, Salmonella enterica, Shigella flexneri and Vibrio parahaemolyticus in ready-to-eat shrimp

This study was conducted to evaluate the inactivation effect of X-ray treatments on Escherichia coli O157: H7, Salmonella enteric (S. enterica), Shigella flexneri (S. flexneri) and Vibrio parahaemolyticus (V. parahaemolyticus) artificially inoculated in ready-to-eat (RTE) shrimp. A mixed culture of three strains of each tested pathogen was used to inoculate RTE shrimp. The shrimp samples were inoculated individually with selected pathogenic bacteria then aseptically placed in sterile plastic cups and air-dried at 22 °C for 30 min (to allow bacterial attachment) in the biosafety cabinet prior to X-ray treatments. The inoculated shrimp samples were then placed in sterilized bags and treated with 0.1, 0.2, 0.3, 0.5, 0.75, 1.0, 2.0, 3.0 and 4.0 kGy X-ray at ambient temperature (22 °C and 60% relative humidity). Surviving bacterial populations were evaluated using a non-selective medium (TSA) with the appropriate selective medium overlay for each bacterium; CT-SMAC agar for E. coli O157: H7, XLD for S. enterica and S. flexneri and TCBS for V. parahaemolyticus. More than a 6 log CFU reduction of E. coli O157: H7, S. enterica, S. flexneri and V. parahaemolyticus was achieved with 2.0, 4.0, 3.0 and 3.0 kGy X-ray, respectively. Furthermore, treatment with 0.75 kGy X-ray significantly reduced the initial microflora on RTE shrimp samples from 3.8 ± 0.2 log CFU g⁻¹ to less than detectable limit (<1.0 log CFU g⁻¹).     

Bioproduction of diosgenin in callus cultures of Trigonella foenum-graecum L.

The production of the steroidal sapogenin, diosgenin, by callus cultures of Trigonella foenum-graecum L. (fenugreek) is described. The levels of this secondary compound were examined by high performance liquid chromatography with a diode-array detector, and its identity was confirmed by mass spectrometry. The levels of diosgenin detected in leaf callus exceeded the levels detected in stem and root calli. The diosgenin levels accumulated in leaf, stem and root calli at 45 days (maximum production) represent 22, 10 and 27%, respectively, of the levels detected in the corresponding organs of the mother plant at 45 days.