紫外诱变选育出芽短梗霉高产普鲁兰糖白化突变菌株

为了发酵获得无色素普鲁兰糖,对菌株Aureobasidium pullulan NG进行紫外诱变,成功获得一株高产普鲁兰糖的白化突变株UVMU3-1。将突变菌株与野生菌株比较发现,其菌体生长能力和分化能力未发生显著改变。突变菌株产出的多糖经红外光谱鉴定为普鲁兰糖,罐发酵实验表明突变菌株产糖能力强于野生菌株。在未经培养基和培养条件优化的情况下,罐发酵的糖转化率可以达到52.78%。突变株UVMU3-1可作为工业发酵普鲁兰糖的潜力菌株。     

复合诱变选育短梗霉多糖高产菌株

以本实验室保存的出芽短梗霉AP8为出发菌株,采用甲基磺酸乙酯(EMS)和紫外线(UV)复合诱变,在EMS终浓度0.4mol/L、作用时间40～60min和30W的紫外灯照射距离30cm、照射时间1.5～2.5min条件下诱变效果好,获得一株稳定遗传的多糖产量高、色素含量低的出芽短梗霉突变株UV60,产量为22.1g/L,对菌落特征和发酵特征的比较发现,突变株UV60在菌落颜色、大小、质地和发酵特性上均明显优于出发菌株AP8。通过对变异株培养基碳氮比和培养基的组成进行单因素和正交试验,其最佳摇瓶发酵培养基组成为：蔗糖50.0g/L、酵母膏1.5g/L、NaCl 1.5g/L、MgSO4 0.3g/L、K2HPO4 2.0g/L、(NH4)2SO4 0.7g/L。采用上述优化的发酵培养基,突变株UV60获得的短梗霉多糖产量为27.24g/L,多糖转化率达54.48%。     

氨基酸对出芽短梗霉发酵生产聚苹果酸的影响

本文研究了添加氨基酸对出芽短梗霉A.pullulans CGMCC3337发酵生产聚苹果酸(PMLA)的影响。通过单因素实验和正交实验分别对氨基酸种类及其添加量进行优化。由单因素实验可知:天冬氨酸(Asp)、亮氨酸(Leu)、缬氨酸(Val)和苏氨酸(Thr)对菌体生长和PMLA合成最有利。由正交实验可知:氨基酸的最优组合为(g/L):天冬氨酸(Asp)0.4、亮氨酸(Leu)0.4、缬氨酸(Val)0.4、苏氨酸(Thr)0.4。在最优组合条件下获得的PMLA产量和分子量分别达到了57.89 g/L和8879 u,比未添加氨基酸获得的PMLA产量和分子量分别提高了40.92%和45.20%。      

出芽短梗霉发酵生产聚苹果酸的研究

为研究芽短梗霉生物合成聚苹果酸的优化工艺条件,采用间歇培养法研究聚苹果酸的发酵过程。测定出芽短梗霉细胞生长和聚苹果酸产物生成曲线,并考察碳源、氮源、CaCO3、pH、摇床转速等因素对聚苹果酸生成的影响,得出出芽短梗霉发酵生产聚苹果酸的优化工艺条件是:葡萄糖120g/L,丁二酸铵3g/L,CaCO330g/L,pH5.5,摇床转速220r/min,温度25℃,发酵培养6d。在此工艺条件下,聚苹果酸的产量达到16.58g/L。聚苹果酸和出芽短梗霉菌体生长呈现一定的相关性。     

聚苹果酸高产菌的筛选与鉴定

从校园周边取样进行了聚苹果酸(Poly malic acid,PMA)高产菌株的分离筛选.经离心管发酵初筛获得了21株产PMA菌株,并初步判断编号Ⅰ-2、Ⅰ-13a、Ⅲ-16菌株的产PMA能力较强,经摇瓶发酵复筛,确定编号Ⅰ-13a菌株的产PMA能力最强,产量达到(43.08±0.36)g/L.通过形态学特征观察和分子...     

表面活性剂对出芽短梗霉发酵生产聚苹果酸的影响

探究不同表面活性剂对出芽短梗霉CGMCC3337合成聚苹果酸的影响,并对最佳影响因子的作用机制做初步探究。结果发现,十二烷基硫酸钠(sodium dodecyl sulfate,SDS)和曲拉通X-100对聚苹果酸的合成有抑制作用;吐温80和吐温60在低浓度时有利于聚苹果酸的合成,最适添加量均为2 g/L;添加吐温80后,聚苹果酸的产量为31.36 g/L,较对照组提高30.5%。     

基于出芽短梗霉发酵法制备β-聚苹果酸

通过改变出芽短梗霉Aureobasidium pullulans的培养与发酵的工艺条件,实现β-聚苹果酸的生成量和分子量的提高。试验表明,最佳培养条件和培养组分为：100 g/L葡萄糖,35 g/L蛋白胨,2 g/L丁二酸铵,0.1 g/L KH₂PO₄,0.3 g/L MgSO₄·7H₂O,0.5 g/L KCl, 0.05 g/L MgSO₄,20 g/L CaCO₃,0.5 g/L亮氨酸,pH值4.0,发酵温度25℃,培养时间6 d。在该条件下进行发酵培养,β-PMLA的产量提高到24.3 g/L,分子量提高到8 948 Da。     

纤维素酶高产菌株的诱变选育

以绿色木霉13010为出发菌株,利用诱变因子的协同作用,对其进行了诱变育种,得到酶活力较高的突变菌株绿色木霉GL13010。实验结果表明：紫外线、亚硝酸钠诱变因子对绿色木霉13010菌体细胞的致死作用表现出相似的趋势,在一定范围内都与诱变剂量呈线性正相关。在协同诱变条件下,多轮反复诱变绿色木霉13010后,菌株的酶活力有大幅提高,最终筛选得到了产纤维素酶活力单位提高了70．63％的菌株-GL13010。     

出芽短梗霉聚苹果酸发酵条件的优化

在5 L发酵罐上,对出芽短梗霉PMLA发酵条件进行了研究,确定出芽短梗霉PMLA发酵的最优条件。由试验结果可知:优化的发酵温度为分阶段调节,即0~24 h设定发酵温度为30℃,24 h以后调节发酵温度为25℃;搅拌转速400 r/min;通风比1∶1.2。在此条件下,出芽短梗霉PMLA发酵获得的最大生物量为38.7 g/L;聚苹果酸产量为45.2 g/L;生产强度为0.38 g/(L·h)和PMLA分子量为8 412 Da。     

复合诱变选育出芽短梗霉高产菌株

以出芽短梗霉（Aureobasidium pullulans）AS3．0933为出发菌株,采用紫外-光照、亚硝酸、硫酸二乙酯诱变方法,分别研究了单一诱变和复合诱变对AS3．0933菌株对多糖和色素产量的影响。试验结果表明,紫外-光照交替处理的最佳条件为紫外7min-光复活5min-紫外9min-光复活5min-紫外11min-光复活5min;亚硝酸诱变最佳条件为亚硝酸浓度0．05mmol／L、50s;DES处理最佳条件为DES浓度2％、50min;复合诱变途径为紫外．光照诱变1代→紫外-光照诱变2代→亚硝酸诱变1代→亚硝酸诱变2代→DES诱变1代,此诱变处理得到的菌株多糖产量达到20．22g／L,是出发菌株的2．77倍,发酵液颜色浅绿色,发酵液最终pH4．09,连续传代多次,其产量性状无显著变化。     

反向高效液相色谱测定发酵液中的聚苹果酸

采用高效液相色谱柱AlltimaTMC18(4.6 mm×150 mm,4μm)上定量测定发酵生产的聚苹果酸,流动相为乙腈和0.025 mol/L磷酸二氢钾混合溶液(磷酸调pH 2.5)(V:V=5:95),流速1.0 mL/min,检测波长210 nm,柱温25℃,进样量5μL。发酵液经离心除菌体、纯沉除多糖、水解处理后进样,可以将其中的L-苹果酸完全分离定量。采用液相方法的回收率为98.70%~100.65%,RSD为0.4~1.11%。采用试剂盒的方法的回收率为96.7~97.23%,RSD为0.57~1.19%。可见,液相的精确度和试剂盒相差不大。但液相的价格相对比试剂盒要便宜很多,说明该法是测定发酵液中聚苹果酸的一种很有效的方法。     

Grafting of Poly(Methacrylic Acid) on Starch and Poly(Vinyl Alcohol)

Grafting of methacrylic acid (MAA) on starch, poly(vinyl alcohol) (PVA), and a mixture of starch and PVA, using a potassium persulfate/ sodium thiosulfate redox initiation system was carried out. Polymerization was studied with respect to graft yield, homopolymer formation and total conversion. These polymerization criteria were found to depend largely on the concentration of both MAA and initiators, duration and method of polymerization. The results reveal a number of interesting points which reflect the impact of the condition of the treatment. The main product of the polymerization reaction [poly(MAA)‐starch/PVA graft copolymer] was formed and precipitated during polymerization and can be easily separated by filtration as pure product. Application of these copolymers to cotton fabric was also carried out to evaluate the suitability of such modified products as sizing agents.     

共轭亚油酸高产菌株的诱变选育

共轭亚油酸在抗癌、减少脂肪沉积、延缓动脉硬化等方面表现出来功效,推动了共轭亚油酸生产的研究。本研究以寻找到的共轭亚油酸的生成菌株德氏乳杆菌保加利亚亚种为出发菌株,采用紫外线、硫酸二乙酯、亚硝基胍进行多次及复合诱变处理,以提高菌株Ldb2生成共轭亚油酸的能力,获得了315UU、98DD及71UN突变菌株,使共轭亚油酸的生成能力较出发菌株提高幅度在43.04%～59.56%。     

Physicochemical Properties and Digestion Characteristics of Corn Starch Esterfied by Malic Acid

The objective of this study was to evaluate the effects of different degree of substitution on structural characteristics and crystalline properties of resistant starch esterfied by L‐malic acid. With the deepening of the esterification reaction, malate starches particles became larger, particle surface cracks and grooves increased which led to a decline in whiteness of malate starches. With the increase in the degree of substitution (DS), the initial phase transition temperatures (To) and endothermic enthalpies (ΔH) of malate starch gradually decreased. The XRD results indicated that with the increase of DS, the diffraction peak at 15.1° disappeared in the spectrum. When the DS of malate starches reached 0.116, the content of resistant starch (RS) accounted for the majority of the total starch.     

Influence of Citric Acid on the Properties of Glycerol‐plasticized dry Starch (DTPS) and DTPS/Poly(lactic acid) Blends

In the presence of citric acid (CA), one‐step extrusion processing is used to prepare poly(lactic acid)/thermoplastic dry starch (PLA/DTPS) blends (50/50, %, w/w) in a single‐screw extruder. The rheological study proves that CA decreases the viscosity of both DTPS and of DTPS/PLA blends. The low viscosity increases the dispersion and decreases the interfacial tension between DTPS and PLA, as shown by scanning electron microscopy (SEM). In the presence of CA, the tensile strength of DTPS/PLA reaches 41 MPa—similar to that of pure PLA—because of improved dispersion and compatibility. At the same time, CA increases not only the degradation of starch, but also the interaction between DTPS and PLA, as detected by Fourier transform infrared (FTIR) spectroscopy. The blend containing CA has a higher thermal stability. The water absorption of DTPS and DTPS/PLA blends is also studied.     

Inhibition of Listeria monocytogenes and Salmonella by Combinations of Oriental Mustard,Malic Acid,and EDTA

The antimicrobial activities of oriental mustard extract alone or combined with malic acid and EDTA were investigated against Salmonella spp. or Listeria monocytogenes at different temperatures. Five strain Salmonella or L. monocytogenes cocktails were separately inoculated in Brain Heart Infusion broth containing 0.5% (w/v) aqueous oriental mustard extract and incubated at 4 °C to 21 °C for 21 d. For inhibitor combination tests, Salmonella Typhimurium 02:8423 and L. monocytogenes 2–243 were individually inoculated in Mueller Hinton broth containing the mustard extract with either or both 0.2% (w/v) malic acid and 0.2% (w/v) EDTA and incubated at 10 °C or 21 °C for 10 to 14 d. Mustard extract inhibited growth of the L. monocytogenes cocktail at 4 °C up to 21 d (2.3 log₁₀ CFU/mL inhibition) or at 10 °C for 7 d (2.4 log₁₀ CFU/mL inhibition). Salmonella spp. viability was slightly, but significantly reduced by mustard extract at 4 °C by 21 d. Although hydrolysis of sinigrin in mustard extract by both pathogens was 2 to 6 times higher at 21 °C than at 4 °C to 10 °C, mustard was not inhibitory at 21 °C, perhaps because of the instability of its hydrolysis product (allyl isothiocyanate). At 21 °C, additive inhibitory effects of mustard extract with EDTA or malic acid led to undetectable levels of S. Typhimurium and L. monocytogenes by 7 d and 10 d, respectively. At 10 °C, S. Typhimurium was similarly susceptible, but combinations of antimicrobials were not more inhibitory to L. monocytogenes than the individual agents.     

产共轭亚油酸植物乳杆菌的筛选、鉴定与诱变

从传统泡菜中筛选得到1 株乳酸菌lp15 能够合成共轭亚油酸(CLA),经16S rRNA 全序列分析法和API 系统鉴定法鉴定为植物乳杆菌(Lactobacillus plantarum)。利用人工诱变方法,以lp15 为出发菌株,采用紫外线、硫酸二乙酯(DES)依次诱变处理,经进一步液体发酵复筛获得多株突变菌株,CLA合成能力较出发菌株提高了29.3%～52.2%。其中lp15-2-1 突变菌株为CLA 生成能力最高菌株,MRS 培养液中添加0.2mg/mL LA 培养48h,CLA 产量达30.13μg/mL。经气相色谱(GC)检测分析,产物中cis9, trans11- 共轭亚油酸(c9, t11-CLA)占76.5%,trans10, cis12-共轭亚油酸(t10,c12-CLA)占23.5%。     

产γ-氨基丁酸乳酸菌的筛选及诱变育种

利用乳酸菌分离培养基从酸菜汁中分离菌株。经过初筛、复筛后得到的菌株Lp-Lw-131有较好的产γ-氨基丁酸(GABA)能力。对菌株进行形态学鉴定和生理生化实验确定该菌为植物乳杆菌,编号为Lp-Lw-131。利用菌株体内的谷氨酸脱羧酶(GAD)将L-谷氨酸钠脱羧转化成GABA,用比色法测定GABA的产量为0.917g/L。以Lp-Lw-131为出发菌株进行紫外线和硫酸二乙酯(DES)诱变,以致死率为标准确定最佳诱变条件为：紫外照射距离30cm,照射时间90s;DES体积分数为25%醇溶液,处理时间20min,诱变后获得一株突变株Lp-Lw-131-34。连续传代10次后遗传性状稳定,平均GABA产量为1.815g/L,是出发菌株的1.979倍。     

聚谷氨酸的微生物法制备及其水凝胶应用简介

研究中分离得到1株产聚谷氨酸(PGA)的芽孢杆菌,对菌种进行了分类鉴定,包括生理生化实验、Bi-olog-System4.20和16S rRNA基因序列分析,将其命名为Bacillus licheniformisNK-03。对该菌产聚谷氨酸的发酵条件进行了优化,发酵合成PGA的产率为11g/L。PGA溶液经60Co-γ射线照射后形成的水凝胶有很强的吸水性,可吸收2000倍以上体积的水分。