兽疫链球菌NW-162发酵生产透明质酸的研究

在摇瓶中进行了兽疫链球菌诱变株NW-162发酵生产透明质酸的工艺研究,通过正交实验优化了最佳培养基组成,并考察了发酵过程中发酵温度、培养时间、pH值、装料系数等条件对该菌株发酵生产透明质酸的影响。实验表明:碳源及氮源对发酵过程影响最显著,优化所得最佳培养基组成为:葡萄糖40 g/L,复合氮源20 g/L,MgSO42g/L,钠盐3 g/L;在36℃、pH值7.0、装料系数为0.4的工艺条件下,发酵至27—30 h时达到最优发酵效果,收率可达0.464 g/L,比优化前提高2倍。     

透明质酸产生菌发酵培养基及培养条件优化

透明质酸具有保湿能力以及润滑等功效，在软骨、皮肤、脐带和鸡冠中含量极高，且在化妆品和护肤品方面、控制癌症以及新型药物载体设计方面的应用极其广泛。为了继续探究微生物摇瓶发酵下提高透明质酸产量的营养和培养条件，实验对一株兽疫链球菌菌株通过单因素和正交实验法进行发酵培养基及培养条件优化，最终确定兽疫链球菌的最佳发酵条件为：发酵温度37℃、初始pH值7.4、发酵时间为16 h,最佳培养基配比为葡萄糖3%,牛肉膏4.5%,MgSO₄·7H₂O 0.03%,异甘草素0.09%。     

高产量、高分子量透明质酸发酵条件优化

研究了搅拌转速、初糖浓度及通气量对兽疫链球菌Streptococcus zooepidemicus WSH24发酵生产透明质酸的影响. 研究结果表明，搅拌转速对透明质酸产量及分子量影响很大，搅拌转速为200 r/min时透明质酸产量达到5.3 g/L，平均分子量达到1.88×106 Da，产率系数为0.13 g/g；初始葡萄糖浓度为65.8 g/L时有利于透明质酸的生产，产量达5.9 g/L，平均分子量达1.90×106 Da，产率系数为0.17 g/g；通气量对透明质酸的发酵也有较大影响，通气量为1.2 L/(min·L)时透明质酸的产量及分子量均高于0.5 L/(min·L)时的发酵结果.     

表面活性剂对麦草同步糖化发酵转化乙醇的影响

研究了5种非离子型表面活性剂(BSA, Tween-20, Tween-80, PEG-4000, PEG-6000)促进麦草同步糖化发酵的效果. 结果表明,5种表面活性剂均能促进麦草同步糖化发酵,以Tween-20效果最为显著. 反应体系中添加Tween-20可降低酶用量而保持乙醇浓度基本相同. 在pH 5.0、温度37℃、底物浓度50 g/L及Celluclast 1.5 l用量25 FPU/g、Novozym 188用量15 IU/g的反应体系中,添加0.03 g/g Tween-20,反应72 h,乙醇浓度达到18.7 g/L,比未添加表面活性剂的体系提高了14.0%,反应时间缩短了12 h.     

摇瓶补加葡萄糖对放线酮产生菌株发酵生产放线酮的影响

在摇瓶条件下研究了补加葡萄糖对放线酮产生菌YIM41004发酵生产放线酮的影响。摇瓶发酵结果表明:以中6%葡萄糖为初始浓度通过在稳定期(发酵48小时)添加30 g/L的葡萄糖能够提高菌体合成抗生素的能力,使放线酮的产量提高36%。     

产朊假丝酵母发酵生产谷胱甘肽的氨基酸添加策略

研究了添加氨基酸对产朊假丝酵母(Candida utilis WSH02-08)合成谷胱甘肽(Glutathione,GSH)的影响,结果表明,两阶段添加氨基酸能显著提高GSH的发酵水平.摇瓶中发酵10h添加4mmol/L L-半胱氨酸,16h添加混合氨基酸(L-谷氨酸8 mmo/L,L-半胱氨酸8 mmol/L,甘氨酸12 mmol/L),GSH产量和胞内GSH含量分别为290.1 mg/L和3.22%.在3 L发酵罐中,将上述氨基酸添加策略与高密度培养技术相结合,36 h流加葡萄糖的同时添加20 mmol/LL-广胱氨酸,45 h添加混合氨基酸(L-谷氨酸40 mmo/L,L-半胱氨酸40 mmol/L,甘氨酸60 mmol/L),GSH产量和胞内GSH含量分别达1725.3 mg/L和3.29%,分别比高密度培养提高了111.4%和100.6%.     

透明质酸发酵过程控制的研究

进行了兽疫链球菌NW-162高密度发酵HA的工艺研究,通过发酵过程中不同饱和度的溶解氧和不同pH调控方法对该菌株发酵生产透明质酸的影响进行了研究。实验表明,采用30%饱和度的溶解氧和在发酵过程的0~30 h,调pH 7.2,发酵后期调pH 6.8的调控方法,OD660可达0.84,透明质酸产量为0.532 g/L。在此条件下,有利于细胞生长和产物表达,降低乙酸等有害代谢副产物积累。     

L-谷氨酸发酵的变温控制工艺研究

以黄色短杆菌GDK-9为供试菌株,首先考察了不同的培养温度(30~36℃)对L-谷氨酸摇瓶发酵的影响。结果发现,在34℃条件下菌体生长情况最好,且L-谷氨酸产量最高,可达86g/L。基于上述结果,研究了3种变温控制模式下L-谷氨酸摇瓶发酵过程。得出如下结论:0~6h发酵温度为34℃,6h后每隔6h提高1℃,并采用这种温度控制方式进行5L自控发酵罐试验,36h后可积累L-谷氨酸130g/L,比同类研究的产量(102 g/L)提高了27%。     

丙酸高产菌株的选育及发酵培养基优化

通过环境压力筛选获得了一株耐受30 g/L丙酸的产酸丙酸杆菌菌株(Propionibacterium acidipropionici WY320),降低了发酵过程中丙酸的反馈抑制作用,采用正交实验设计优化了发酵培养基. 结果表明,发酵培养基最适的玉米浆、酵母膏和(NH4)2SO4浓度分别为60, 10和7.5 g/L. 该条件下,摇瓶培养耐酸菌株的发酵周期为240 h,丙酸产量为49.35 g/L,较优化前提高72.98%,产率为0.21 g/(L×h); 5 L发酵罐培养的发酵周期为168 h,丙酸产量达51.96 g/L,产率为0.31 g/(L×h),较摇瓶培养提高47.62%,优于文献报道水平.     

透明质酸发酵过程控制的研究

进行了兽疫链球菌NW-162高密度发酵HA的工艺研究,通过优化了发酵过程中不同饱和度的溶解氧和不同PH调控方法对该菌株发酵生产透明质酸的影响。试验表明:采用30%饱和度的溶解氧和在发酵过程的0～30小时,调pH 7.2,发酵后期调pH 6.8的调控方法,OD660可达0.84,透明质酸产量为0.532 g/L。在此条件下,有利于细胞生长和产物表达,降低乙酸等有害代谢副产物积累。     

Statistical modeling and optimization for enhanced hyaluronic acid production by batch culture of Sreptococcus zooepidemicus via the supplement of uracil

This work is aimed to achieve the optimal hyaluronic acid (HA) production by batch culture of Streptococcus zooepidemicus via the supplement of nucleotide bases using response surface methodology (RSM). First, the influence of nucleotide bases (adenine, guanine, cytosine, thymine, and uracil) on microbial HA production was investigated using fractional factorial design (FFD). By a 2⁵⁻² FFD, uracil was found to be the most significant factor for cell growth and HA production, while the other nucleotide bases were shown to have no significant effects on cell growth and HA production. Also, the impact of uracil on cell growth and HA production was further investigated by RSM, where two variables were considered: uracil concentration and supplement time. The optimal uracil concentration and supplement time were found to be 0.051g/L and 7h, respectively, and the predicted maximal HA production reached 6.42g/L. The maximal HA production increased from 5.0g/L of the control without uracil supplement to 6.31g/L at the optimal conditions in validation experiments.     

Statistical modeling and optimization for enhanced hyaluronic acid production by batch culture of Sreptococcus zooepidemicus via the supplement of uracil

This work is aimed to achieve the optimal hyaluronic acid (HA) production by batch culture of Streptococcus zooepidemicus via the supplement of nucleotide bases using response surface methodology (RSM). First, the influence of nucleotide bases (adenine, guanine, cytosine, thymine, and uracil) on microbial HA production was investigated using fractional factorial design (FFD). By a 2^5-2 FFD, uracil was found to be the most significant factor for cell growth and HA production, while the other nucleotide bases were shown to have no significant effects on cell growth and HA production. Also, the impact of uracil on cell growth and HA production was further investigated by RSM, where two variables were considered: uracil concentration and supplement time. The optimal uracil concentration and supplement time were found to be 0.051 g/L and 7 h, respectively, and the predicted maximal HA production reached 6.42 g/L. The maximal HA production increased from 5.0 g/L of the control without uracil supplement to 6.31 g/L at the optimal conditions in validation experiments.     

兽疫链球菌NW-162发酵产生的透明质酸分离纯化研究

对兽疫链球菌诱变株NW-162发酵液中透明质酸(HA)的分离提取工艺方法进行了对比研究。采用乙醇沉淀分离透明质酸、链霉蛋白酶酶解结合氯仿除去蛋白质及经氯代十六烷吡啶分级分离工艺,结果表明:乙醇与上清液的体积比为2.5∶1.0时沉淀透明质酸25 h最为经济;酶解结合氯仿去除蛋白质较氯仿单独作用时,透明质酸产量及纯度均有一定提高,再经氯代十六烷吡啶分级分离后,可得纯度为71.5%、蛋白质质量分数2.8%、产量0.747 g/L、相对分子质量725×103的透明质酸产品。     

酶法转化制备L-瓜氨酸

利用粪链球菌精氨酸脱亚胺酶转化L-精氨酸制备L-瓜氨酸。考察了菌龄、转化温度等多种因素对精氨酸脱亚胺酶活力的影响。酶法制备L-瓜氨酸的最适工艺条件是:菌体发酵时间20 h,转化温度37℃,转化液起始pH为6.0,ρ〔十六烷基三甲基溴化铵(CTAB)〕=0.3 g/L使酶活提高了414%。c(Co2+)=10-3mol/L使酶活增高约50%,c(Cu2+)=10-2mol/L或c(Zn2+)=10-2mol/L使酶活下降约50%。Ca2+、Mg2+和Mn2+对酶活影响较小。     

温度对产甘油假丝酵母产甘油发酵过程的影响

研究了温度对产甘油假丝酵母分批发酵生产甘油及其生长动力学的影响。结果表明:在温度为28—36℃时,由于发酵周期随温度升高而显著缩短,导致细胞生长、甘油合成和葡萄糖消耗的比速率也随温度升高逐渐增加;当温度为32℃时最适于产甘油假丝酵母合成甘油,甘油产量、得率和产率分别达到120.3 g/L,0.523 g/g,1.43 g/(L.h);应用Logistic方程对细胞生长动力学进行了模拟,获得不同温度下的生长动力学参数;根据细胞生长动力学参数,得到28—36℃时甘油分批发酵过程中细胞质量浓度同温度、时间之间的一般关系式,经验证该模型在28—36℃范围内可用于预测不同温度下的细胞生长情况。     

Aqueous dispersion of surfactant-modified multiwalled carbon nanotubes and their application as an antibacterial agent

The dispersing power of different surfactant-modified multiwalled carbon nanotubes (MWCNTs) and their effect on the antibacterial activity were examined. Three surfactants, including hexadecyltrimethylammonium bromide (CTAB), triton X-100 (TX-100) and sodium dodecyl sulfate (SDS) were tested. UV–vis absorbance, transmission electron microscopy and Fourier transform infrared spectroscopy were used to characterize the dispersion of MWCNTs in the aqueous phase, showing that the surfactant molecules had been adsorbed onto the MWCNTs’ surface. Among the three surfactants, TX-100 and CTAB provided maximum and minimum dispersion, respectively. The surfactant-modified MWCNTs exhibited different antibacterial activities to Streptococcus mutans. The fluorescence images showed that the surfactant-modified MWCNTs were not only capable of capturing bacteria and forming cell aggregates, but also killing them. Under the same concentration and treatment time, the CTAB-modified MWCNTs exhibited the strongest antibacterial activity compared to the TX-100 and SDS-modified MWCNTs. The optical density growth curves and viable cell number determined by the plating method suggested that the antibacterial activity of all surfactant-modified MWCNTs was both concentration- and treatment time-dependent.     

蔗糖、乳酸及KH2PO4对乳链菌肽合成的影响

在恒pH、厌氧条件下，研究了蔗糖、乳酸及KH2PO4对L. lactis sp. lactis ATCC11454分批发酵中细胞生长和乳链菌肽合成的影响. 乳链菌肽的合成表现为初级代谢动力学特征. 蔗糖对乳链菌肽的合成具有调控作用，提高蔗糖浓度可以提高细胞浓度及乳链菌肽效价，但过高的蔗糖浓度(>30 g/L)抑制了乳链菌肽的合成. 乳酸作为代谢产物抑制了菌体的生长，同时导致乳链菌肽效价的下降，乳链菌肽对菌体的得率系数YN/X随起始乳酸浓度的增加而减小，表明乳酸对乳链菌肽合成的影响更大. KH2PO4在恒pH条件下对乳链菌肽的合成并没有促进作用.     

表面活性剂的混合乳化性质在退浆中的应用

将表面活性剂的混合乳化性质应用到棉线退浆中,讨论了表面活性剂复配比例、温度、pH值及处理时间等因素对退浆的影响。结果表明,表面活性剂退浆法最佳工艺条件为:十二烷基硫酸钠(SDS)30 g/L,AEO-9 5 g/L,十六烷基三甲基溴化铵(CTAB)30 g/L,OP乳化剂10 g/L,pH6.5~7.5,温度70~80℃,处理时间60 min,在此条件下,棉线失重率为14.2%,白度为80.6。     

Templated Synthesis of Gold Nanorods (NRs): The Effects of Cosurfactants and Electrolytes on the Shape and Optical Properties

Seeded growth of gold nanorods (NRs) has been accomplished in a micellar medium containing mixed surfactants or a high salt concentration. Cetyl trimethylamoniumbromide (CTAB) forms micelles upon which the growth of rod shaped gold nanoparticles occurs. AgNO₃ is introduced into the growth solution to enhance the formation of NRs. The roles of non-ionic surfactants such as Tween and Triton, and of electrolytes such as sodium chloride and potassium chloride have been examined. As the concentration of these additives in the growth solution is increased, the aspect ratio of the NRs increases to a critical limit, after which it decreases again. Upon carefully controlling the content of Triton X-100 or Tween 20 in the growth solution, these non-ionic surfactants assisted in fine-tuning the shape of gold NRs (e.g. rectangular or “dogbone”). The growth pattern of the NRs fits into the model of a soft template formed by the mixture of CTAB and non-ionic surfactants.     

Impact of Phosphate,Potassium, Yeast Extract,and Trace Metals on Chitosan and Metabolite Production by Mucor indicus

In this study the effects of phosphate, potassium, yeast extract, and trace metals on the growth of Mucor indicus and chitosan, chitin, and metabolite production by the fungus were investigated. Maximum yield of chitosan (0.32 g/g cell wall) was obtained in a phosphate-free medium. Reversely, cell growth and ethanol formation by the fungus were positively affected in the presence of phosphate. In a phosphate-free medium, the highest chitosan content (0.42 g/g cell wall) and cell growth (0.66 g/g sugar) were obtained at 2.5 g/L of KOH. Potassium concentration had no significant effect on ethanol and glycerol yields. The presence of trace metals significantly increased the chitosan yield at an optimal phosphate and potassium concentration (0.50 g/g cell wall). By contrast, production of ethanol by the fungus was negatively affected (0.33 g/g sugars). A remarkable increase in chitin and decrease in chitosan were observed in the absence of yeast extract and concentrations lower than 2 g/L. The maximum chitosan yield of 51% cell wall was obtained at 5 g/L of yeast extract when the medium contained no phosphate, 2.5 g/L KOH, and 1 mL/L trace metal solution.