S-腺苷蛋氨酸和谷胱甘肽联产发酵中盐胁迫的作用

摇瓶条件下考察不同的盐(NaCl,Na2SO4,KCl,K2SO4)胁迫对产朊假丝酵母发酵联产S-腺苷蛋氨酸(SAM)和谷胱甘肽(GSH)的影响。结果发现适当浓度的Na+和K+对SAM和GSH合成具有部分促进作用,而Cl-的作用则相反。以Na2SO4为代表,考察分批发酵条件下盐胁迫的作用,结果表明:在酵母细胞生长后期(15 h)添加10 g/L Na2SO4,SAM、GSH以及二者的最大联产量为252.5、285.9和521.9 mg/L,比对照分别提高了8.8%、22.6%和13.9%。最后分别从能量代谢和发酵动力学角度对分批发酵的结果进行了分析。     

响应面法优化产朊假丝酵母培养及干燥工艺

本研究旨在优化产朊假丝酵母液体培养参数及干燥保护剂配方,提高产朊假丝酵母液体培养数量,制备出高复苏率的活性干酵母。以装液量、转速、温度和培养时间为影响因素,设计单因素试验,并采用Box-Behnken试验设计及响应面分析法优化产朊假丝酵母液体培养方案。在此条件下培养酵母,以L-谷氨酸钠、乳糖、脱脂奶粉为影响因素进行单因素保护试验,并采用响应面分析法优化干燥保护剂的组合。结果表明,产朊假丝酵母最佳培养条件为装液量45 mL/250 m L,转速200 r/min,温度30℃,培养时间24 h。在此条件下,培养的产朊假丝酵母数量可以达到9.34×10~8CFU/mL;最佳保护剂组合1%L-谷氨酸钠、12%脱脂奶粉、6%乳糖,经干燥后,产朊假丝酵母复苏率达到81.9%。此时活菌数7.65×10~8CFU/g,比未加保护剂组提高了3.83倍。     

过氧化氢胁迫促进产朊假丝酵母合成谷胱甘肽

谷胱甘肽(GSH)在生物细胞抵御外界环境条件的刺激和胁迫时起到非常重要的作用。考察了不同时间不同浓度过氧化氢胁迫和过氧化氢连续胁迫对产朊假丝酵母合成GSH的影响, 发现低浓度过氧化氢的连续胁迫对GSH的合成有明显促进作用。进一步在发酵罐上应用了低浓度过氧化氢(36 mmol/L)持续胁迫策略, 最终GSH产量为922 mg/L, 胞内GSH含量为1.64%, 比对照分别提高了7%和35%。     

过氧化氢胁迫促进产朊假丝酵母合成谷胱甘肽

谷胱甘肽(GSH)在生物细胞抵御外界环境条件的刺激和胁迫时起到非常重要的作用。考察了不同时间不同浓度过氧化氢胁迫和过氧化氢连续胁迫对产朊假丝酵母合成GSH的影响, 发现低浓度过氧化氢的连续胁迫对GSH的合成有明显促进作用。进一步在发酵罐上应用了低浓度过氧化氢(36 mmol/L)持续胁迫策略, 最终GSH产量为922 mg/L, 胞内GSH含量为1.64%, 比对照分别提高了7%和35%。     

产朊假丝酵母发酵生产谷胱甘肽的补料研究

为了实现产朊假丝酵母( Candida utilis WSH02-08)的高密度培养和提高谷胱甘肽 ( glutathione, GSH)产量,在分批发酵研究的基础上,考察了指数速率流加和DO-stat反馈流加对产朊假丝酵母合成GSH的影响.结果表明,采用指数速率流加可获得高细胞密度,但不利于GSH的合成,而采用DO-stat反馈流加较适宜细胞积累GSH.因此,提出并运用了指数速率-DO-stat组合流加策略,即采用指数速率流加实现细胞高密度培养,采用DO-stat反馈流加实现GSH的高积累,细胞量、GSH产量和胞内GSH含量分别为82.5 g/L、1120.6 mg/L和1.46%,实现了高细胞密度和高胞内GSH含量的相对统一.     

培养方式对富硒产朊假丝酵母性能的影响

在摇瓶和5 L发酵罐水平上分别考察亚硒酸钠浓度及其添加方式对高性能(高有机硒含量和高谷胱甘肽含量)富硒产朊假丝酵母制备的影响.结果表明:亚硒酸钠添加质量浓度为15 mg/L时,产朊假丝酵母具有较好的富硒效果,但一次性添加对酵母细胞有较大的毒害作用.采用分批次添加亚硒酸钠的方法获得了较好的制备高性能富硒产朊假丝酵母的培养方式:发酵起始添加L-蛋氨酸10 mmol/L,并在发酵过程的12和15 h分别添加亚硒酸钠10和5 mg/L.在此培养方式下,产朊假丝酵母胞内谷胱甘肽和有机硒含量分别达到172.3 mg/L和1194 μg/g.     

氮源及碳氮比对产朊假丝酵母合成谷胱甘肽的影响

研究了N源对产朊假丝酵母细胞生长和谷胱甘肽(GSH)合成的影响。在此基础上,分别以(NH4)2SO4和尿素作为单一N源,摇瓶条件下研究了不同C、N比对GSH发酵的影响。结果发现尿素有利于细胞生长,而(NH4)2SO4更有利于GSH的合成,并且酵母细胞在利用这2种N源合成GSH时,各自具有最佳的C、N比((NH4)2SO4为8.3 mol/mol,尿素为5.6 mol/mol)。最佳C、N比下的GSH分批发酵结果显示,尿素是更合适的N源,最终细胞干质量和GSH产量可以分别达到16.48 g/L和246.4 mg/L。最后分别采用发酵动力学模型和代谢网络分析对该结果产生的原因进行了定量解释。     

溶氧及pH对产朊假丝酵母分批发酵生产谷胱甘肽的影响

在7 L发酵罐中研究了溶氧和pH对产朊假丝酵母分批发酵生产谷胱甘肽的影响。结果表明,当葡萄糖浓度为30 g/L且通气量控制在5 L/min时,搅拌转速达到300 r/min即可满足细胞生长和谷胱甘肽合成对溶解氧的需求。不同pH控制方式对谷胱甘肽分批发酵的影响有较大差异。不控制pH时,细胞干重和谷胱甘肽产量比控制pH为55的发酵分别低27%和95%,且有50%的谷胱甘肽向胞外渗漏。研究了将pH控制在4.0、4.5、5.0、5.5、6.0和6.5的谷胱甘肽分批发酵过程,发现在pH 5.5时谷胱甘肽总产量最高。用前期研究建立的动力学模型模拟了不同pH (4.0～6.5)下的分批发酵过程,并从动力学角度解释了pH对细胞生长和谷胱甘肽合成的影响。     

休哈塔假丝酵母发酵木糖制乙醇过程研究

木质纤维素原料水解产物的主要成分是葡萄糖和木糖,其中葡萄糖很容易发酵,致使木糖成为木质纤维素发酵的关键,休哈塔假丝酵母(Candida shehatae)1766是自然界木糖发酵性能较好的天然酵母之一。研究了发酵温度、发酵时间、接种量、初始pH值、摇床转速等因素对休哈塔假丝酵母1766发酵木糖生产乙醇的影响,由正交试验初步确定了休哈塔假丝酵母发酵木糖制乙醇工艺的适宜条件为好氧条件,发酵时间为2d,发酵温度为28℃,摇床转速为150r/min,初始pH值为5,此时乙醇收率最高可达68.62%。     

微胶囊固定化酵母培养的研究*

进行了NaCS-PDMDAAC微胶囊固定化酒精酵母和产朊假丝酵母的实验研究。考察了这两种酵母的培养规律,发现微胶囊固定化酒精酵母的产酒精情况与游离培养基本一致,在连续发酵16批后,仍具有良好的性能。同时固定化产谷胱甘肽(GSH)的产朊假丝酵母的研究也表明固定化培养GSH产量与游离细胞产量相近。     

Influence of culture conditions on glutathione production by <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

A strategy of experimental design using a fractional factorial design (FFD) and a central composite rotatable design (CCRD) were carried out with the aim to obtain the best conditions of temperature (20–30°C), agitation rate (100–300 rpm), initial pH (5.0–7.0), inoculum concentration (5–15%), and glucose concentration (30–70 g/l) for glutathione (GSH) production in shake-flask culture by Saccharomyces cerevisiae ATCC 7754. By a FFD (2^5–2), the agitation rate, temperature, and pH were found to be significant factors for GSH production. In CCRD (2²) was obtained a second-order model equation, and the percent of variation explained by the model was 95%. The results showed that the optimal culture conditions were agitation rate, 300 rpm; temperature, 20°C; initial pH, 5; glucose, 54 g/l; and inoculum concentration, 5%. The highest GSH concentration (154.5 mg/l) was obtained after 72 h of fermentation.     

Production, optimization growth conditions and properties of the xylanase from Aspergillus carneus M34

Growth conditions, including incubation times, temperature, agitation rate and initial pH of medium, that affect xylanase production by Aspergillus carneus M34 were studied sequentially use the classical “change-one-factor-at-a-time” method. Our results showed that there was a similar trend between cellular xylanase activity and extracellular xylanase activity. The optimal conditions for xylanase production, different from their cell growth, were on the third day, 30 °C, 100 rpm and pH 4, respectively, in this test. Response surface methodology (RSM) was further introduced to optimize the cultivation conditions and to evaluate the significance of these factors. The optimal cultivation conditions predicted from canonical analysis of this model were achieved by incubation at 35.08 °C with an agitation rate of 111.9 rpm and an initial pH of 5.16. In addition, temperature was the most critical factor for xylanase production by A. carneus M34. Xylanase activity of 22.2 U/mL was verified using the predicted optimal conditions and confirmed the fitness and applicability of the model. The optimal temperature and pH of the crude xylanase activity was observed at 60 °C and acidic pH, respectively. Sustained xylanase activity in the crude extract was also detected over a broad range of pH from 3 to 10. Considering its higher specificity toward agricultural wastes, especially corn cob and coba husk, this strain can be used to develop low-cost media for the mass-production of xylanase.     

酿酒酵母突变株J-X25胞内合成GSH的研究

以筛选得高产谷胱甘肽(GSH)产生酵母甲硫氨酸缺陷型变株J-X25为试验菌株。对其培养条件进行研究,结果表明：发酵培养基的最适初始pH值为6.0、最佳发酵温度为30℃、最佳装液量为100ml/500ml、接种量10%、摇床转速为220r/min。在酵母细胞培养到对数期,加入过氧化氢刺激细胞发生应激反应和乳酸钠作为表面活性剂改变细胞通透性,GSH总量达到0.253g/L,比不添加两者情况下的GSH产量高出52％。结果表明优化培养条件后,J-X25胞内积累GSH比出发株提高79％。     

Lipoxygenase-another pathway for glutathione conjugation of xenobiotics: A study with human term placental lipoxygenase and ethacrynic acid.

In this study, we examined the ability of human term placental lipoxygenase (HTPLO) to catalyze glutathione (GSH) conjugate formation from ethacrynic acid (EA) in the presence of linoleic acid (LA) and GSH. HTPLO purified by affinity chromatography was used in all the experiments. The results indicate that the process of EA-SG is enzymatic in nature. The reaction shows dependence on pH, the enzyme, and the concentration of GSH, LA, and EA. The optimal assay conditions to observe a maximal rate of EA-SG formation required the presence of 0.3 mM LA, 0.2 mM EA, 2.0 mM GSH, and approximately 300 microg HTPLO in the reaction medium buffered at pH 9.0. Under the experimental conditions employed, the reaction exhibited K(m) values of 1.1 mM, 200 microM, and 130 microM for GSH, LA, and EA, respectively. The estimated specific activity of HTPLO-catalyzed EA-GS formation was approximately 4.4 +/- 0.4 micromol/min/mg protein. This rate is more than twofold greater than the rate noted for the reaction mediated by the purified human term placental glutathione transferase. Under physiologically relevant conditions (20 microM LA, 2.0 mM GSH, at pH 7.4), HTPLO produced EA-SG at 56% of the maximal rate noted under optimal assay conditions. Nordihydroguaiaretic acid, the classical inhibitor of different lipoxygenases, significantly blocked the reaction. It is proposed that free radicals are involved in the process of EA-SG formation by HTPLO. The evidence gathered in this in vitro study suggests for the first time that lipoxygenase present in the human term placenta is capable of EA-SG formation.     

Two-step sequential optimization for production of ionic liquid stable cellulase from Bacillus subtilis I-2

The cost-effective bulk production of cellulases with desirable characteristics e.g., ionic liquid (IL)-stability, thermal, and pH stability is highly desirable. This study reports the optimization of cultural and environmental variables for enhanced production of an IL-stable, broad pH range, and thermo-stable cellulase from Bacillus subtilis I-2 employing low-cost agro-industrial wastes. Furthermore, combined interactive effects of different variables on enzyme yield were investigated using response surface methodology. The optimal levels of carbon and nitrogen sources were determined (% w/v, wheat bran 2.0, potato peel 1.5, cotton seed cake 0.8, and soybean meal 0.8) for enhanced cellulase yield. Further, optimization of environmental variables (temperature 48.41?°C, pH 7.0, and agitation rate 180 rpm) lead to overall 4.1-fold (76– 315.90 U/ml) enhancement of cellulase yield.     

Influence of nutritional and environmental factors on ethanol and endopolygalacturonase co-production by Kluyveromyces marxianus CCEBI 2011

Ethanol and endopolygalacturonase (endoPG) are simultaneously produced by the yeast Kluyveromyces marxianus CCEBI 2011. The aim of this study was to determine the optimal combination of seven environmental and nutritional variables, as well as the influence of each one, with respect to the fermentation process in yeast cultures in which sugarcane juice was the substrate. Simplex sequential optimization showed that after 15 runs the optimal conditions were: pH, 4.6; temperature, 31 oC; total reducing sugars (TRS), 125 g/l; (NH(4))(2)SO(4), 2.48 g/l; (NH(4))(2)HPO(4), 2.73 g/l; CaCl(2), 0.33 g/l and MgSO(4)·7H(2)O, 0.54 g/l. Under these conditions, the ethanol concentration was 47.6 g/l and endoPG concentration was 9.8 U/ml, which represented increases of 22% and 10%, respectively, over the concentrations obtained under suboptimal conditions. Temperature and (NH(4))(2)SO(4) supplementation were the most significant factors influencing the co-production process.     

Cross-talk between sulfur assimilation and ethylene signaling in plants

Sulfur (S) deficiency is prevailing all over the world and becoming an important issue for crop improvement through maximising its utilization efficiency by plants for sustainable agriculture. Its interaction with other regulatory molecules in plants is necessary to improve our understanding on its role under changing environment. Our knowledge on the influence of S on ethylene signaling is meagre although it is a constituent of cysteine (Cys) required for the synthesis of reduced glutathione (GSH) and S-adenosyl methionine (SAM), a precursor of ethylene biosynthesis. Thus, there may be an interaction between S assimilation, ethylene signaling and plant responses under optimal and stressful environmental conditions. The present review emphasizes that responses of plants to S involve ethylene action. This evaluation will provide an insight into the details of interactive role of S and ethylene signaling in regulating plant processes and prove profitable for developing sustainability under changing environmental conditions.     

Optimisation of physical factors on the production of active metabolites by Bacillus subtilis 355 against wood surface contaminant fungi

A Surface Response Model was used to study the effect of pH, temperature and agitation on growth, sporulation and production of antifungal metabolites by Bacillus subtilis CCMI 355.Strong agitation, temperature between 27 and 34 °C and pH 6 favoured cell growth. Alkaline pH, strong agitation and temperature between 28 and 34 °C favoured spore formation. No relationship was found between sporulation and the production of antifungal metabolites. According to the model, pH 8, 37 °C and the absence of agitation were the optimal conditions for the production of broad-spectrum antifungal metabolites against Botrytis cinerea, Penicillium expansum, Trichoderma sp, Trichoderma harzianum, Trichoderma koningii and Trichoderma virgatum.In situ assays using green wood impregnated with Bacillus subtilis CCMI 355 inoculated in Yeast Extract Glucose Broth medium in the conditions above, displayed an efficient protection against wood surface contaminant fungi.     

Cultural Conditions and Some Properties of the Lipase of Humicola lanuginosa S-38

The cultural conditions for the production of thermostable lipase by a thermophilic fungus Humicola lanuginosa S-38 were investigated. The optimal cultural conditions to obtain the maximum yield of thermostable lipase with a 600-liter stainless steel fermentor were as follows: optimal medium- 2.0% soluble starch, 5.0% corn steep liquor, 0.2% K₂HPO₄, 0.1% MgSO₄·7H₂O, 0.5% CaCO₃, 0.5% soybean oil, 0.005% deforming agent (Adecanol LG-109); optimal fermentation conditions- temperature 45°C; rate of agitation 300 rpm; initial pH 7.0; rate of aeration 1/1 volume per volume of medium per minute. The optimal pH of the crude lipase preparation for the hydrolysis of the polyvinyl alcohol-emulsified olive oil was 8.0 and the optimal temperature was 60°C. It retained 100% of activity with the heat treatment at 60°C for 2 hr, but at 70°C for 20 min only 35% activity retained.