热带假丝酵母发酵生产木糖醇的研究

对热带假丝酵母 (C tropicalis )As2 1 776发酵木糖醇的营养条件进行了初步研究。初始木糖浓度在 80g/L附近时木糖醇转化率较高 ,限制性供氧条件下有利于木糖醇积累。酵母膏和蛋白胨是比较适合产木糖醇的有机氮源 ,而酵母膏更利于酵母细胞生长。培养基中添加 2 g/L的(NH4 ) 2 HPO4 、2～ 6g/L的NaCl、1～ 3g/L的KH2 PO4 、0 1～ 0 3 g/L的MgSO4 ·7H2 O能提高木糖醇的转化率     

热带假丝酵母利用酒糟水解液发酵生产木糖醇的初步研究

对热带假丝酵母(C.tropicalis)AY91009利用酒糟(丢糟)水解液发酵木糖醇进行了初步研究。结果表明:最佳发酵时间48h,最佳种子龄22h。摇瓶分批发酵工艺条件的最佳组合是:起始pH5.5,接种量15%(v/v),装液量135mL,氮源加入量为10mL含有10g/L酵母膏和20g/L蛋白胨的有机氮源。除水解液本身含有的木糖外,1/10的葡萄糖加入量(w/w)有利于菌体生长和木糖醇的转化,蔗糖则会抑制木糖醇的生成。培养基中添加6g/L的NaCl、3g/L的KH2PO4、0.2g/L的MgSO4.7H2O有利于木糖醇的积累。     

正交旋转回归试验优化木糖醇发酵培养基

利用旋转回归法研究热带假丝酵母 (Candidatropicalis)木糖醇发酵的 2个因素 :葡萄糖和酵母膏用量对木糖醇转化率的影响 ,根据木糖醇转化率依葡萄糖和酵母膏用量的回归方程分析表明 ,培养基中添加葡萄糖能提高木糖醇产物转化率 ,而酵母膏对提高产物转化率的作用不显著。研究同时表明 ,添加葡萄糖后能降低培养基中酵母膏的使用量 ,节约成本。根据回归方程寻优得出 :当木糖质量浓度 13 0 g/L时 ,葡萄糖用量 14 2 6g/L ,酵母膏用量3 40 g/L时 ,由木糖生成木糖醇的产物转化率最高     

土壤中产木糖醇酵母菌株的筛选其发酵条件优化

本文以木糖为唯一碳源从土壤中筛选得到可以耐受高浓度木糖的菌株,再经过复筛选出一株高产木糖醇的酵母菌株Y-9。经高效液相色谱(HPLC)和红外扫描分析,确定菌株Y-9发酵利用木糖转化得到的主要产物为木糖醇。通过单因素实验、正交试验等手段,对菌株Y-9发酵产木糖醇的培养基组分和发酵条件进行了优化,进一步提高了目的菌株的木糖醇产率和转化率,确定了菌株Y-9摇瓶发酵木糖转化木糖醇的最优培养基和发酵条件。在木糖初始浓度为200 g/L,氮源为酵母膏3.0 g/L,硫酸铵2.0 g/L,玉米浆10.0 mL/L,硫酸镁0.1 g/L,初始pH为6.0,转速为180 r/min,接种量为4%的条件下,菌株Y-9的木糖醇产率为160 g/L左右,木糖醇生成速率为1.67 g/L.h,木糖/木糖醇转化率达到80%以上,是一株具有良好工业化研究开发价值的木糖醇生产菌株。     

普鲁兰酶产生菌的筛选鉴定与发酵条件的研究

从海洋中分离出了一株产普鲁兰酶活性较高的菌株BCT-1,初步鉴定为不动杆菌(Acinetobacter sp.)。通过对发酵培养基以及发酵条件的优化,使普鲁兰酶的酶活力达到2.347 U/mL。优化后的发酵培养基成分如下:0.02 g/mL玉米淀粉,0.01 g/mL~0.012 5 g/mL酵母膏,0.001 g/mL KH2PO4,0.000 5 g/mL MgSO.47H2O及0.000 01 g/mL FeSO4.7H2O。最佳培养条件为:发酵初始pH 6.0,接种量为8%,培养温度30℃,500 mL摇瓶装液量为150 mL,摇瓶转速为200 r/min,发酵周期72 h。     

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。     

热带假丝酵母发酵法生产木糖醇的研究

目的利用热带假丝酵母研究发酵木糖生产木糖醇的发酵条件。方法采用摇瓶发酵对发酵生产条件,如培养基中初始木糖浓度、接种量和通气量、氮源、pH等进行优化,通过测定发酵液中木糖的残留量、木糖醇的转化率来确定适合的发酵工艺。结果通过实验得到最佳培养基条件为:初始木糖50g/L,蛋白胨5g/L,酵母粉10g/L,硫酸镁0.5g/L、磷酸二氢钾5g/L,硫酸铵1g/L;最佳发酵条件为:pH 6.0,摇瓶发酵装液量50mL/250mL,转速200 r/min,发酵温度30℃,发酵时间28h。结论优化了木糖醇的发酵工艺。     

生物转化法生产木糖醇的细胞增殖培养基优化

以木糖为底物利用酵母细胞转化生产木糖醇,研究细胞增殖培养基中不同种类的碳源、氮源和微量元素及其添加量对酵母细胞生长和木糖转化率的影响。结果表明,当碳源为木糖和葡萄糖添加量分别为1%时,木糖醇浓度为49.6g/L;当无机氮源为蛋白胨且浓度为2%时,木糖转化时间为60h,木糖醇浓度达到58g/L;微量元素为磷酸二氢钾浓度为0.1%时,木糖的转化时间为48h,此时木糖醇浓度达到59g/L。     

利用木糖高产乙醇酵母菌发酵条件的研究

以蒙假丝酵母JS-73为出发菌株,逐渐增加底物中木糖浓度,对该菌株利用木糖产乙醇的能力进行了驯化,并优化该菌利用木糖生产乙醇的工艺和培养基成分.结果表明,驯化后,木糖利用率为67.21％,酒精产量达到7.41 g/L.确定了发酵培养基的最优组合为:木糖60 g/L,酵母粉0.6 g/L,K2HPO41.0 g/L,MgSO4·7H2O 0.4 g/L,在该条件组合下,菌株JS-73的乙醇产量为10.27 g/L,是理论产量的37.21％.确定了发酵最优条件为:温度31℃,pH5,转速70 r/min,接种量11％,装液量120 mL/250 mL,在此条件下,乙醇产量达最高,为18.95 g/L.     

一株耐高温乳酸菌的发酵条件优化

选用乳酸菌发酵生产L-乳酸,利用SAS软件的Plackett-Burman设计和Box-Benhnken设计优化了发酵培养基,以期提高L-乳酸的产量。最终确定最优培养基为(g/L),乙酸钠1.69、蛋白胨6.33、酵母膏6.63、葡萄糖30、吐温80 1、玉米浆10、柠檬酸二铵2、KH2PO40.28、MnSO4.7H2O 0.2、MgSO4.7H2O 0.2、CaCO310。在上述条件下,发酵乳酸菌的L-乳酸产量为12.533 g/L,比优化前提高74.07%。     

Ethanol production by a new pentose-fermenting yeast strain, Scheffersomyces stipitis UFMG-IMH 43.2, isolated from the Brazilian forest

The ability of a recently isolated Scheffersomyces stipitis strain (UFMG-IMH 43.2) to produce ethanol from xylose was evaluated. For the assays, a hemicellulosic hydrolysate produced by dilute acid hydrolysis of sugarcane bagasse was used as the fermentation medium. Initially, the necessity of adding nutrients (MgSO(4)·7H(2)O, yeast extract and/or urea) to this medium was verified, and the yeast extract supplementation favoured ethanol production by the yeast. Then, in a second stage, assays under different initial xylose and cell concentrations, supplemented or not with yeast extract, were performed. All these three variables showed significant (p < 0.05) influence on ethanol production. The best results (ethanol yield and productivity of 0.19 g/g and 0.13 g/l/h, respectively) were obtained using the hydrolysate containing an initial xylose concentration of 30 g/l, supplemented with 5.0 g/l yeast extract and inoculated with an initial cell concentration of 2.0 g/l. S. stipitis UFMG-IMH 43.2 was demonstrated to be a yeast strain with potential for use in xylose conversion to ethanol. The establishment of the best fermentation conditions was also proved to be of great importance to increasing the product formation by this yeast strain. These findings open up new perspectives for the establishment of a feasible technology for ethanol production from hemicellulosic hydrolysates.     

Xylitol production from rice straw hemicellulose hydrolyzate by polyacrylic hydrogel thin films with immobilized Candida subtropicalis WF79

Xylose from rice straw hemicellulose hydrolysate was fermented for xylitol production using Candida subtropicalis WF79 cells immobilized in polyacrylic hydrogel thin films of 200 mum thickness. Cell immobilization was conducted by first suspending the yeast cells in a mixture of 2-hydroxyethyl methacrylate (HEMA, hydrophilic monomer), polyethylene glycol diacrylate (PEG-DA, crosslinking agent), and benzoin isopropyl ether (photoinitiator). The mixture was then allowed to form polyacrylic hydrogel thin films, between two pieces of glass sheets, by UV-initiated photopolymerization. The hemicellulose of rice straw was hydrolyzed using dilute sulfuric acid at 126 degrees C. The hydrolysate was neutralized with calcium hydroxide. After separating the solid residues and calcium sulfate precipitates by filtration, the hydrolysate was treated with charcoal to partially remove potential inhibitory substances, followed by vacuum concentration to obtain solutions of desired xylose concentrations for yeast fermentation. The thin films with immobilized yeast cells were submerged in the xylose solution from rice straw hydrolysate for fermentation in an Erlenmeyer flask. The maximum yield was 0.73 g of xylitol per gram of xylose consumed. In the 52.5-day long durability test, after 40 d of repeated batchwise operation, the fermentation activities of the cell immobilized in thin films began to decline to a yield of 0.57 g/g at the end.     

响应面法优化不同型态热带假丝酵母发酵生产木糖醇的工艺

利用Design Expert软件对菌丝型和酵母型热带假丝酵母发酵生产木糖醇实验进行设计及结果分析,建立木糖和木糖醇浓度与4个关键因子(菌型、发酵温度、pH、初始木糖浓度)的二次多项式回归模型,并对模型进行解析。结果表明:菌丝型热带假丝酵母转化木糖为木糖醇的能力高于酵母型;升高发酵温度,有利于木糖转化为木糖醇,而pH升高对转化过程并没有明显促进;发酵液中初始木糖浓度与木糖转化率呈正相关关系;获得最佳发酵工艺条件为菌种采用菌丝型酵母,发酵温度37℃,pH8,初始木糖浓度60mg/mL,此时木糖醇浓度达到17.21mg/mL。     

固定化热带假丝酵母发酵氨浸稻秸水解液生产木糖醇

采用海藻酸钙固定化热带假丝酵母细胞发酵氨水浸泡稻秸半纤维素水解液生产木糖醇。为了提高木糖醇的转化率,对发酵条件进行了研究。发酵在250 mL锥形瓶中进行。向水解液中补充适量氮源和营养盐等营养物质提高了木糖醇的生产速率,但木糖醇转化率没有因此而提高。适宜的初始pH和细胞干浓度分别为4-5和1.22 g/L。在这些条件下,进行了固定化细胞重复法较高浓缩度水解液的试验。结果发现,固定化细胞能在初始木糖浓度为104.2 g/L的水解液中重复批式发酵5次,木糖醇平均得率和生产速率分别为0.737 g/g和0.533 g/(L.h)。     

驯化和胶囊包裹的假丝酵母LF04发酵玉米芯水解液生产木糖醇

玉米芯的酸水解液是木糖醇生产的重要原料,但是该水解液中含有糠醛、酚类等对后续微生物发酵有毒害作用的化合物。本研究从土壤中分离了一株似假丝酵母LF01,通过驯化和微胶囊包裹来提高其对水解液的抗性。结果表明通过多次驯化并进行包裹的假丝酵母LF04能在玉米芯水解液中不经任何脱毒处理发酵木糖生产木糖醇。在pH5.5 溶氧为 0.15vvm 的条件下发酵 88h,木糖转化率为 76%,木糖醇浓度达 61.768g/L。远高于其出发菌株。该结果表明采用该方法有望用于木糖醇的工业化生产。     

Increase of xylitol productivity by cell-recycle fermentation of Candida tropicalis using submerged membrane bioreactor

Candida tropicalis, an osmophilic strain isolated from honeycomb, produced xylitol at a maximal volumetric productivity of 3.5 g l(-1) h(-1) from an initial xylose concentration of 200 g l(-1). Even at a very high xylose concentration, e.g., 350 g l(-1), this strain produced xylitol at a moderate rate of 2.07 g l(-1) h(-1). In a fed-batch fermentation of xylose and glucose, 260 g l(-1) xylose was added, and the xylitol production was 234 g l(-1) for 48 h, corresponding to a rate of 4.88 g l(-1) h(-1). To increase xylitol productivity, cells were recycled in a submerged membrane bioreactor with suction pressure and air sparging. For each recycle round in cell-recycle fermentation, the average concentration of xylitol produced, fermentation time, volumetric productivity, and product yield were 180 g l(-1), 19.5 h, 8.5 g l(-1) h(-1), and 85%, respectively. When cell-recycle fermentation was started with the cell mass concentrated twofold after batch fermentation and performed for 10 recycle rounds, we achieved a very high productivity of 12 g l(-1) h(-1). The productivity and total amount of xylitol in cell-recycle fermentation were 3.4- and 11.0-fold higher than those in batch fermentation, respectively.     

The level of glucose-6-phosphate dehydrogenase activity strongly influences xylose fermentation and inhibitor sensitivity in recombinant Saccharomyces cerevisiae strains

Disruption of the ZWF1 gene encoding glucose-6-phosphate dehydrogenase (G6PDH) has been shown to reduce the xylitol yield and the xylose consumption in the xylose-utilizing recombinant Saccharomyces cerevisiae strain TMB3255. In the present investigation we have studied the influence of different production levels of G6PDH on xylose fermentation. We used a synthetic promoter library and the copper-regulated CUP1 promoter to generate G6PDH-activities between 0% and 179% of the wild-type level. G6PDH-activities of 1% and 6% of the wild-type level resulted in 2.8- and 5.1-fold increase in specific xylose consumption, respectively, compared with the ZWF1-disrupted strain. Both strains exhibited decreased xylitol yields (0.13 and 0.19 g/g xylose) and enhanced ethanol yields (0.36 and 0.34 g/g xylose) compared with the control strain TMB3001 (0.29 g xylitol/g xylose, 0.31 g ethanol/g xylose). Cytoplasmic transhydrogenase (TH) from Azotobacter vinelandii has previously been shown to transfer NADPH and NAD(+) into NADP(+) and NADH, and TH-overproduction resulted in lower xylitol yield and enhanced glycerol yield during xylose utilization. Strains with low G6PDH-activity grew slower in a lignocellulose hydrolysate than the strain with wild-type G6PDH-activity, which suggested that the availability of intracellular NADPH correlated with tolerance towards lignocellulose-derived inhibitors. Low G6PDH-activity strains were also more sensitive to H(2)O(2) than the control strain TMB3001.