玉米浆发酵产生物丁醇的氨基酸代谢动力学模拟

为了深入挖掘利用丙酮丁醇梭菌产生物丁醇过程中氨基酸代谢的动态过程，探究利用廉价氮源玉米浆中的氨基酸用于丙酮丁醇梭菌产生物丁醇的生产策略，寻找生产丁醇的高效率廉价氮源来降低发酵生产成本。该研究首先利用高通量测序技术对玉米浆中微生物多样性进行分析；同时基于丙酮丁醇梭菌（Clostridium acetobutylicum）生产丙酮-丁醇-乙醇（Acetone-Butanol-Ethanol，ABE）碳代谢动态模型的基础上，构建氨基酸代谢模型，以此模拟15种氨基酸在利用木糖为碳源发酵生产ABE中的氨基酸代谢过程，并对氨基酸的代谢与丙酮丁醇梭菌的生物量以及ABE的合成相关性关系进行冗余分析；通过模型预测实际生产中利用玉米浆发酵时氨基酸的消耗过程。结果表明，梭状芽胞杆菌属（Clostridium）占细菌总数的68.76%，是玉米浆中的优势菌群；最佳参数校正后构建了氨基酸代谢模型，模拟值与试验值有较好拟合度；11种氨基酸（苯丙氨酸、苏氨酸、异亮氨酸、亮氨酸、蛋氨酸、缬氨酸、酪氨酸、甘氨酸、丝氨酸、精氨酸、天冬酰胺）在培养过程中迅速消耗用于细胞生长和溶剂生成，3种氨基酸（脯氨酸、组织胺、天冬氨酸）保持稳定状态，同时发酵过程中谷氨酰胺积累；冗余分析表明其中5种氨基酸对发酵产物及生物量影响具有相关性（P<0.05），相关性排序从大到小依次为丝氨酸、甘氨酸、亮氨酸、缬氨酸、天冬酰胺；模拟预测玉米浆中缬氨酸、甘氨酸、丝氨酸在发酵过程中基本被消耗，推测其为发酵后期的营养限制性因子。该结论可证实玉米浆可作为丙酮丁醇梭菌发酵丁醇的优势氮源，为丙酮丁醇梭菌的氨基酸代谢调控及下一步利用并优化玉米浆作为氮源生产生物丁醇提供一定的理论参考和数据支撑。     

家蚕肠道产蛋白酶菌株的分离与鉴定及其发酵条件

为探明家蚕肠道中产蛋白酶细菌的种类分布及其作用效果,本研究以家蚕(Bombyx mori)4龄幼虫肠道内容物为材料,采用牛肉膏蛋白胨培养基和酪蛋白培养基分离筛选产蛋白酶细菌菌株,利用16SrDNA序列分析鉴定其种属,并研究其产酶能力和产酶活力较高菌株的最适发酵条件。结果获得3株产蛋白酶菌株皓月NA1、951NA3和951NA6,均归属于不动杆菌属(Acinetobacter),其中皓月NA1号细菌产酶能力最强,最佳产酶量为29.5U/mL。以玉米粉10000mg/L、黄豆粉10000mg/L、MgSO4400mg/L、NaC115000mg/L和K2HPO41000mg/L作为发酵培养基成分,在35℃、起始pH9.0、装液量为80mL/150mL、180r/min振荡培养48h的优化发酵条件下,皓月NA1号细菌最大产酶量可达50U/m L。研究结果对家蚕肠道微生物的分布及肠道益生菌的作用效果调控有着十分重要的意义。     

纳豆菌液态发酵蛤蜊制备ACE抑制肽的工艺研究

为了开发海洋水产源降血压多肽,以蛤蜊为原料,利用纳豆菌液态发酵法制备血管紧张素转化酶(ACE)抑制肽,并以ACE抑制率和总肽含量为控制指标,在单因素试验基础上,采用五因素三水平正交试验优化发酵工艺。结果表明,最佳发酵条件为:发酵温度45℃,发酵时间24h,接种量5%,料液比1∶25,蔗糖添加量10%。在此发酵条件下,发酵产物对ACE抑制率达80.49%,总肽含量达11.53mg·m L-1。本研究结果为蛤蜊的高值化利用提供了科学依据。     

一株高活性纤维素降解细菌的筛选鉴定及酶学特性

利用小麦/玉米秸秆还田土壤样品,通过富集培养和刚果红平板染色法筛选分离出纤维素降解细菌XWS-12;对分离的菌株进行16S rRNA基因序列系统发育分析,初步鉴定为伯克氏菌属(Burkholderia),定名为Burkholderia sp.XWS-12。以玉米秸秆和麸皮为碳源,研究了氮源、发酵时间、初始发酵温度、培养基初始pH等条件对该伯克氏菌产纤维素酶的影响。结果显示,该菌株产纤维素酶最适氮源为硝酸钠,培养时间为60 h,培养温度为37℃,培养基初始pH为4,该菌株的CMC酶活力最高,可达25 U/ml。其粗酶液的最适反应温度为50℃,最适反应pH为5,在pH 4~8的范围内酶活力较稳定。粗酶液的热稳定较差,当温度超过50℃时,该酶活力显著下降;当温度为50℃时,保温1 h,该酶活力损失53%。     

水培条件下玉米幼苗利用钾长石作钾源的研究

为研究利用细菌分解钾长石作为植物钾源的可行性,进行了玉米水培正交实验。单因素分析表明:培养体系内钾细菌投量并非越多越好,以2%较合适;钾长石粉投量与解钾量正相关;植物根系分泌物和振荡对细菌解钾促进作用明显;而外加可溶钾源对细菌解钾有抑制作用。对细菌、钾长石投量、pH和玉米苗数四因素正交分析表明:细菌解钾最优条件为细菌投量2%,钾长石粉为5 g L-1,pH=5,玉米为3棵,从而为细菌钾肥的开发提供参考。     

猴头菇液体菌种培养基筛选试验

选用４种不同原料组成的培养基，进行猴头菇液体发酵试验结果表明：玉米粉、蛋白胨、葡萄糖培养基为最佳，菌丝球小，直径为１－１．５ｍｍ，浓度大，每１００ｍｌ发酵液菌丝球达到１１１５３．３个／１００ｍｌ；其次为麸皮、蛋白胨、葡萄糖培养基，菌丝球直径为１．５－２ｍｍ，每１００ｍｌ发酵液菌丝浓度为１８２６．７个／１００ｍｌ；麸皮、黄豆饼粉、蛋白胨、葡萄糖培养基上的菌丝球直径为１－２ｍｍ，每１００ｍｌ发酵液菌丝     

有机磷分解细菌的选育及其发酵条件的研究

采用有机磷培养基,从土壤中得到6个具有较强分解有机磷能力的菌株。以菌株A5作为出发菌株,进行了紫外线诱变,获得解磷能力明显提高的菌株AY09,其解磷量为17.84 mg.mL-1,比出发菌株A5提高了87.0%。对菌株AY09的发酵条件进行了初步研究,结果表明,碳源以1%玉米粉最好,氮源以2%NH4Cl为最佳,最适培养温度35℃,装液量为50 mL/250 mL,在发酵过程中,其发酵液的pH呈现先降低后升高的趋势。     

4株苯磺隆降解菌的分离鉴定及其生长特性

从长期受农药苯磺隆污染的土壤中通过采用富集培养分离技术得到4株以苯磺隆为唯一碳源生长的细菌,分别将其命名为B1、B2、B3和B4。通过观察这4种菌株的形态学特征,研究其生理生化特性以及分析其16S rDNA序列,初步鉴定菌株B1为铜绿假单胞菌(Pseudomonas aeruginosa),B2为戴尔福特菌(Delftia sp.),B3为微杆菌(Microbacterium sp.),B4为产碱杆菌(Alcaligenes sp.)。并通过研究温度、初始pH值、接种量、苯磺隆初始浓度、培养基体积、氮源、碳源、Mg2+浓度等因素对4种菌株生长情况的影响,确定了菌株的最佳生长条件。结果显示,B1菌株的最适温度为35℃,其他3株菌株均为30℃。菌株B3最适pH为8.0,其余3株菌株均为pH7.0。B1和B3菌株最适接种量为15%,B2和B4最适接种量为10%。菌株B3最适苯磺隆初始浓度为100mg·L-1,其余菌株最适苯磺隆初始浓度均为200mg·L-1。4株菌株最适培养基体积均为75mL,最适氮源均为硝酸铵,最适碳源均为葡萄糖。B2菌株最适Mg2+浓度为100mg·L-1,其余3株菌株均为200mg·L-1。B1和B4菌株最适NaCl浓度为20g·L-1,B2菌株NaCl浓度为5~30g·L-1,B3菌株最适NaCl浓度为50g·L-1。该结果为利用微生物对农药苯磺隆污染的土壤进行原位生物修复提供理论依据。     

重组球孢白僵菌表达目标产物类枯草杆菌蛋白酶的发酵特性研究

采用单因子筛选和正交试验,研究了碳源、氮源、微量元素及无机盐等营养成分对重组球孢白僵菌(Beauveria bassiana)菌株Bb0062-15-4-CDEP-1产生目标产物类枯草杆菌蛋白酶CDEP-1的影响,并通过摇瓶发酵和30 L发酵罐发酵对其发酵特性进行了研究.结果表明,其优化发酵培养基为2.0%玉米粉,1.0%麦麸,0.25%豆粕粉,0.4%NaNO3,0.1%MgSO4·7H2O.摇瓶发酵结果表明,在对数生长期,随着菌体生物量的增加,CDEP-1产量上升,二者呈一定的平行关系;当菌体生长到稳定期,CDEP-1产量继续上升,并达到产酶高峰;此后,随着菌体生长的衰退,CDEP-1产量出现快速下降趋势.扩大培养时,30 L发酵罐中60 h产酶量最高,比摇瓶培养(168 h)缩短了108 h,单位体积的产酶量比摇瓶培养提高80%.结果对研究和利用该球孢白僵菌重组菌株的代谢产物,提高真菌杀虫剂的杀虫效果奠定了基础.     

芽胞杆菌高产纤维素酶菌株的诱变选育与培养基优化

为获得高产纤维素酶菌株,采用紫外(UV)诱变和紫外-亚硝基胍(UV-NTG)复合诱变方法对新疆吐鲁番地区土壤中分离得到的产纤维素酶菌株芽胞杆菌C-8进行诱变筛选,并通过二次正交旋转组合试验和响应面试验对诱变筛选得到的菌株进行培养基的优化。结果表明,UV诱变菌株UV-5和UV-NTG比出发菌株C-8纤维素酶活分别提高了1.15倍和3.23倍;当发酵培养基中碳源浓度为3%、氮源浓度为1.5%、吐温-80的浓度为0.15%时,纤维素酶活达到453.20 U·m L-1,是出发菌株C-8的5.49倍和复合诱变菌株UV-NTG-10的1.7倍。本研究结果为纤维素酶的扩大发酵以及后期工业化生产提供了理论依据。     

Endogenous organic acid variations in different chickpea (Cicer arietinum L.) genotypes

Abstract

Changes in cropping systems during the past century have led to selective pressure on weed flora. Species and ecotypes with characteristics enabling them to survive in high-input farmland have increased in numbers, at the cost of plants lacking these characters. Since the 1950s, the perennial weed species Cirsium arvense (L.) Scop. and Sonchus arvensis L. have mainly been controlled by the herbicide group synthetic auxins like MCPA. During recent decades, C. arvense seems to have become less susceptible to MCPA in both Europe and North America but the reasons are unclear.

To study the importance of selective pressure on weed ecotypes, both short- and long-term studies were carried out in Uppsala, Sweden. The first consisted of two growth-characteristic greenhouse experiments. The hypothesis was that ecotypes of C. arvense and S. arvensis from high-input farmland were different and displayed a more competitive growth pattern than did ecotypes from low-input farmland.

The second study was a field experiment with four ecotypes of C. arvense from low-input farmland to study if selective pressure was in force, over a period of six years. The four ecotypes had different growth characteristics and herbicide sensitivity and they were exposed to crop competition and MCPA treatments during the experimental period. The hypothesis was that ecotypes with a more competitive growth pattern and MCPA tolerance would survive to a greater extent than would other ecotypes. For C. arvense, the results from the growth-characteristic experiment showed that the growth pattern of ecotypes from high-input farmland differed, showing a more directly elongated growth pattern with fewer spines on the leaves compared with ecotypes from low-input farmland, which usually were of rosette-type. Results from the field experiment with C. arvense showed that after six years MCPA-sensitive and/or rosette-type ecotypes had almost disappeared while ecotypes with a more directly elongated growth pattern and less sensitive to MCPA survived to a much greater extent. The conclusion was therefore that when exposed to selective pressure like crop competition and herbicide treatments, ecotypes of C. arvense with a more directly elongated growth pattern and less sensitive to herbicide treatment survived to a greater extent compared with ecotypes missing these traits. Ecotypes from high-input farmland had generally fewer leaf spines than did ecotypes from low-input farmland. This may suggest a trade-off between spine formation and rapid competitive growth. In the growth-characteristic experiment with S. arvensis, no differences between ecotypes from high- and low-input farmland regarding growth characteristics or leaf spines could be detected. This might partly be due to a lower exposure of S. arvensis to selective pressure compared with C. arvense, since S. arvensis generally is less sensitive to MCPA.     

有机酸处理条件对玉米秸秆热解特性的影响

酸洗预处理能有效改善K^+对生物质热解的影响,该文利用热重分析仪和裂解-气相色谱质谱联用仪进行了玉米秸秆的热解试验,研究了不同有机酸酸洗浓度(3%、5%和7%)、酸洗温度(25、50和75℃)和酸洗时间(1、2和3 h)对玉米秸秆热解特性的影响。结果表明:酸洗能显著降低玉米秸秆内在K^+的含量;经过不同条件的有机酸洗预处理后,玉米秸秆的TG/DTG(thermogravimetry/differential thermogravimetry)曲线均向高温段移动,最大热解速率随着酸洗浓度和酸洗温度的增加逐渐增大,随着酸洗时间的增加先增大后降低,在酸洗温度为75℃时,最大热解速率达到最大值15.49%/min;与此同时,玉米秸秆热解主要产物为酚类、酮类和呋喃类化合物,酸洗后,其酚类物质产率明显增加,在酸洗浓度为7%时达到最大值16.75%,而酮类和呋喃类化合物产率减少,分别在酸洗时间为1 h和酸洗浓度为7%时达到最小值0.10%和7.13%。酸洗后,焦炭产率减少,在酸洗浓度为3%时达到最小值18.79%。通过研究不同处理条件下有机酸对玉米秸秆热解特性的影响,为生物质预处理中酸溶液的选择提供了参考。     

Organic Acids and Diffusive Flux of Organic and Inorganic Phosphorus in Sandy-Loam and Clayey Latosols

This study evaluated the effects of organic acids on the diffusive flux of phosphorus (DFP) along time. Treatments were a factorial 2?×?2?×?2?×?2?×?5 design: two soils (clayey Red Latosol and a sandy-loam Red-Yellow Latosol), two organic acids (citric acid, CA, and humic acid, HA), and two phosphorus (P) sources [monopotassium phosphate (KH₂PO₄) and inositol hexaphosphate (IHP)] either with or without heating (100 °C) of the soil. The soil plus treatments, in all combinations, were placed in contact with an anion exchange resin and the P in the resin was measured after 2, 4, 6, 10, and 15 days. The DFP was greater when the soils were treated with CA than when treated with HA. Citric acid was more effective in increasing the DFP from KH₂PO₄, whereas HA was the organic ligand that promoted a larger DFP when the source was IHP.     

Interactive effects of organic acids in the rhizosphere

Organic acids released into the rhizosphere may perform many beneficial functions to the plant including metal detoxification and enhancement of nutrient acquisition. Typically, these organic acids are studied in isolation; however, roots simultaneously exude a cocktail of organic acids and other substances, and their combined impact on rhizosphere processes may be quite different. It has been hypothesized that some exudates may play secondary roles (e.g. inhibitors of microbial activity, blockage of sorption sites), which might enhance the longevity and nutrient-mobilization capacity of others. Here we investigated how the decomposition, sorption and P-solubilizing effects of citrate, malate and oxalate are affected by the presence of malonate and shikimate. We found that in a range of agricultural soils the decomposition of citrate, malate and oxalate was rapid, but not influenced by the presence of large quantities of shikimate or malonate. This suggests that the individual organic acids are taken up by different transport mechanisms or components of the microbial community. At large concentrations, malonate decreased sorption of citrate, malate and oxalate on the soil, whilst shikimate had little effect. The capacity of citrate, malate and oxalate to desorb P was significantly greater in cocktails containing malonate compared with the single organic acid; no effect was seen with shikimate. We conclude that neither malonate nor shikimate at realistic concentrations will significantly affect the biodegradation of citrate, malate or oxalate in the rhizosphere, and while malonate did enhance P desorption, this effect is additive rather than synergistic. Overall, we found little evidence that malonate and shikimate act as secondary regulators of citrate, malate and oxalate behavior in soil.     

Low pH and aluminum tolerance of Bradyrhizobium strains isolated from acid soils in Indonesia

Sixty-seven strains of Bradyrhizobium isolated from soybean plants growing on acid soils in West Java and Sumatra, Indonesia, were examined for the effect of the pH and aluminum concentration on their growth in nutrient media, compared with 61 strains of Bradyrhizobium from soils in Japan. The results in this study indicated that the indigenous population of Bradyrhizobium in the soils of Indonesia showed a large difference in acid- and Al-tolerance from that of Japan. Eighty-five and 48% of the isolates from Japanese soils and Indonesian soils, respectively, were unable to grow in YEM broth at pH below 4.5. The acid-tolerance was correlated with AI-tolerance of the isolates on YEM agar plates at pH 4.4. Seventy-five percent of the isolates that grew in YEM broth at pH 4.5 were also resistant to 400 µM Al on the YEM plates. Acetylene reduction assay of the root nodules revealed that 3 of the acid- and Al-tolerant isolates from Indonesian soils showed a significantly high nitrogen fixation activity.     

Effect of humic acid and fulvic acid based liquid and foliar fertilizers on the yield of wheat crop

Abstract

An organic-mineral liquid fertigation fertilizer containing humic acid, nitrogen (N)–phosphorus (P)–potassium (K), zinc (Zn), sulfur (S), manganese (Mn) and a liquid foliar fertilizer consisting of fulvic acid and gibberellic acids were formulated and applied to wheat. The purpose of this study was to develop an efficient and cost effective liquid and foliar fertilizer and compare their potential with commercially available urea and DAP. The fulvic acid and humic acids were obtained by alkaline extraction of lignite coal. All the treatments were significant over the control. The application of the liquid fertigation fertilizer and liquid foliar fertilizer along with 50?kg of urea per acre showed the best results biological yield (grain plus straw yield). It was found that the highest yield was obtained in T₆ treatment and the second best results were obtained with T₂ treatment, but has a high cost, while treatment T₆ was the most significant economical and yielded a high income when compared to other treatments.     

Plant defence inducers rapidly influence the diversity of bacterial communities in a potting mix

Plant hormones and their functional analogues are used in agriculture to combat plant diseases and pests. These chemicals are generally targeted at shoots, but soils inevitably receive a dose during application. In this study, we used 16S rRNA gene amplicon pyrosequencing to determine whether the diversity of bacterial communities in a potting mix (referred here as ‘model soil’) is influenced by exposure to salicylic acid (SA), methyl jasmonate (MeJA), ethylene (ET) and abscisic acid (ABA). The number of operational taxonomic units (OTUs; richness) and Simpson's Diversity Index values (evenness) associated with each sample was not influenced by the hormone treatments, but changes in community composition were observed. Relative to the control, all hormones more than doubled the abundance of a Limnobacter population, ABA led to a four-fold increase in a Cellvibrio population, ET led to a c. 70% decrease in an Algoriphagus population, and MeJA and ABA applications halved the abundance of a Massilia population. These changes may influence plant productivity.     

Chemical Composition of Ten Blackcurrant (Ribes nigrum L.) Cultivars

Abstract

Ten blackcurrant cultivars were evaluated for some quality components. On average, the sugar content was 9.0%, of which fructose made up 45%, glucose 40% and sucrose 15%. Soluble solids were 15.4% as an average for the ten cultivars in three years. The acid content was 5.1% of fresh weight, 88% was citric acid and 12% malic acid. The ascorbic acid content varied from 67 mg per 100 g fresh fruit in Hedda, to 204 mg per 100 g in Blackdown. Except for Hedda and Øjebyn, which both had low values of ascorbic acid and colour properties, the quality components of the cultivars were found to be within an acceptable range.     

不同来源腐殖酸的组成和性质的研究

本研究从三种有机物料草炭、褐煤、风化煤中提取腐殖酸,对其组成和性质进行了测定,同时对胡敏酸进行酒精沉淀分级。研究结果表明:褐煤胡敏酸氧化度和芳香度最高,其次为风化煤胡敏酸,最后是草炭胡敏酸;风化煤富里酸的氧化度和芳香度最高,其次为褐煤富里酸和草炭富里酸。胡敏酸各级分的回收率均随着级分数的升高而增加。回收率以风化煤胡敏酸最高,依次为褐煤胡敏酸、草炭胡敏酸。     

Soil Humic and Fulvic Acids from Different Land-Use Systems Evaluated By E4/E6 Ratios

Changes in land-use systems such as the introduction of trees on agricultural land can give rise to changes in the physicochemical properties of the soils, also affecting the quantity and quality of organic matter incorporated into the system. The present study assesses humic substances (HS) in the soil such as humic acid (HA) and fulvic acid (FA) by looking at the relationship between the optic densities determined at 465 and 665 nm (E4/E6 ratio). Topsoil samples (0–20 cm) from pine woodlands 60 years of age were compared with agricultural soils of similar age in the central-south region of the Province of Buenos Aires, Argentina. The pH of the topsoil from beneath the pine trees was highly acidic (5.0 vs. 6.2) and a significant increase in the level of organic carbon (OC) was registered. The carbon to nitrogen (C/N) ratio was also higher (by one order of magnitude) beneath the pine trees, although the humification conditions of the soil organic matter (SOM) were good in the soils of both studied land-use systems. The E4/E6 ratio was higher in the HA and FA 2º (second extraction) beneath the pines, indicating a smaller molecular size of the HS bound to the clay minerals. This fact can be attributed to the higher concentration of hydrogen ions beneath the pines and consequently the loss of polyvalent cations, mainly calcium. The most labile organic molecules (FA 1º – first extraction) were of a larger size in soils beneath the pines, most likely owing to a specific characteristic of the Pinus genus, although the fraction in question constitutes a minority fraction among the HS. Clear differences were established between the E4/E6 ratios in HA and FA, making this a highly useful method for determining molecular changes in HS as a result of changes in land use.