利用光合菌发酵对玉米秸杆进行转化的研究*

系统研究了光合菌在氨法处理和非氨处理两种环境下,在厌氧、好氧、以及自然条件下对玉米秸秆的转化。通过发酵液中还原糖与蛋白质浓度的测定结果的比较、判断、优选出一种最适合条件下光合菌对玉米转化的途径。研究表明,在以氨化法处理的玉米秸秆为底物与光合菌的发酵实验中,发酵液中的还原糖和蛋白质的尝试都要比非氨法条件下玉米秸秆为底物与光合菌发酵实验中的发酵液中的不原糖和蛋白质的浓度高。实验结果证明了转化产生的还原糖、蛋白质都是光合菌能利用的营养成分,由此达到利用光合菌转化玉米秸秆的研究目的。     

新分离Microbacterium sp. XT11菌产黄原胶降解酶生产条件的优化研究

新分离Microbacteriumsp.XT11菌能够合成黄原胶降解酶,将植物病原菌野油菜黄单孢菌分泌的毒素因子黄原胶分解,生成具有激发子和抗微生物活性的黄原胶寡糖。实验确认,黄原胶和酵母浸粉分别是XT11菌生产黄原胶降解酶的最适碳源和氮源,获得最高酶活力的最低碳源和氮源浓度均为0.3%。XT11菌生产黄原胶降解酶的最适条件为:培养温度28℃,培养基起始pH7.0,转速150r/min。     

新分离Microbacterium sp．XT11菌产黄原胶降解酶生产条件的优化研究

新分离Microbacterium sp．XT11菌能够合成黄原胶降解酶,将植物病原菌野油菜黄单孢菌分泌的毒素因子黄原胶分解,生成具有激发子和抗微生物活性的黄原胶寡糖。实验确认,黄原胶和酵母浸粉分别是XT11菌生产黄原胶降解酶的最适碳源和氮源,获得最高酶活力的最低碳源和氮源浓度均为0.3％。XT11菌生产黄原胶降解酶的最适条件为：培养温度28℃,培养基起始pH7.0,转速150r／min。     

黄原胶寡糖生物活性的研究

利用黄原胶降解菌Cellulom onassp.XT11生产的黄原胶降解酶,对黄原胶进行生物降解,生产具有不同粘度/还原末端比的黄原胶寡糖,并研究了黄原胶寡糖在清除羟基自由基、植物防卫反应中激活因子活性和对植物病原菌抑制能力等方面的生物活性,结果表明黄原胶寡糖具有清除羟基自由基能力,并能激活植物防卫系统以抵御病原菌的侵染,同时对野油菜黄单孢菌也具有抑菌活性。     

虎掌菌菌丝富硒培养的研究

为生产合适的硒源提供一种思路,以菌丝体生物量、含硒量、还原糖、氨态氮和蛋白质为指标,采用四因素三水平正交设计法优化虎掌菌的富硒发酵条件,探讨不同浓度的硒对虎掌菌固体培养菌丝生长和液体培养产生的生物组分的影响。结果表明,高浓度的硒抑制虎掌菌菌丝体生长;正交试验选择不同的衡量指标,由极差分析得出各因素的影响程度大小,结合证实试验得到以还原糖为指标的最优组合为葡萄糖6%(质量分数)、酵母浸膏3%(质量分数)、KH_2PO_4 0.1%(质量分数)、Na_2SeO_3 0.6 mmol/L,其菌丝体生物量和氨态氮含量较高。与对照相比,加硒后虎掌菌发酵液中氨态氮、还原糖和总糖含量显著增加(P0.05);当硒浓度为0.5 mmol/L时,氨态氮、还原糖和总糖含量均达到最高值。菌丝体生物量和可溶性蛋白质分别在硒浓度为0.2 mmol/L和0.4 mmol/L时达到最大值。虎掌菌富硒培养后,发酵液的营养成分含量会发生变化。     

乙醇-黄原胶耦联两步发酵

初步探索乙醇-黄原胶耦联两步发酵的可行性和生产工艺,即控制乙醇发酵,发酵液去除固形物后蒸馏回收酒精,然后利用酒精糟液中剩余营养物质进行黄原胶发酵。摇瓶和小罐试验证实方案是可行的,耦联发酵工艺优化条件:选择木薯淀粉进行乙醇发酵60 h后的酒精糟液,添加2 g/L KH2PO4,不添加无机N源。在优化条件下,7 L发酵罐中耦联发酵的黄原胶产量达到20 g/L,转化率约为50%。     

黄原胶寡糖的抗氧化性能和非酶糖基化抑制作用研究

分别在酸性和碱性条件下通过氧化降解制备了两种黄原胶寡糖XG-H和XG-OH.红外光谱法对黄原胶寡糖的结构进行表征,凝胶渗透色谱法测定黄原胶寡糖的分子量,紫外可见分光光度法测定黄原胶寡糖的丙酮酸和还原糖含量,考察了两种黄原胶寡糖的抗氧化性能和非酶糖基化(NEG)的抑制作用.结果表明,XG-H和XG-OH都表现出一定的抗氧化能力且XG-OH强于XG-H; XG-OH促进5-羟甲基糠醛(非酶糖基化中间产物)的生成,但可显著抑制非酶糖基化荧光末端产物的生成.而XG-H表现出非酶糖基化促进作用.这可能与两种黄原胶寡糖的丙酮酸和还原糖含量有关.     

应用混料实验设计制备秸秆复合降解菌剂

农业秸秆类废弃物含有大量木质纤维素,该类物质结构稳定,不易降解,为秸秆的合理利用带来诸多困难。本实验尝试利用混料实验设计对筛选出可以共同培养的五种木质纤维素降解菌的配比进行研究,寻求复合发酵降解剂各组分的最佳配比,并分析发酵产品得到适用于不同发酵目的的菌剂。通过对发酵产品中木质素和纤维素降解率及还原糖的含量的分析建立模型,分析预测纤维素降解率最高为35.75%,木质素降解率最高为27%,还原糖含量最高为3.39mg/g。通过优化得出发酵菌剂最优配比为枯草芽胞杆菌12.1%,克鲁斯假丝酵母10%,地衣芽胞杆菌27.2%,变色栓菌10.6%,黄孢原毛平革菌40%。对应三指标的实测值为：35.47%,26.41%和2.37mg/g。     

信息库

1.黄原胶提纯的新方法 野油菜黄单胞菌发酵生产的黄原胶发酵液,首先进行加热处理,随后用溶菌酶再用碱性蛋白酶处理,溶解残余的细胞(或先用碱性蛋白酶再用溶菌酶处理)。然后从处理过的发酵液中回收黄原胶。     

XCCNAU—92发酵生产黄原胶的适宜条件

XCCNA－92发酵生产黄原胶的适宜条件是：好氧,发酵温度为30℃,培养基起始pH为7.0,接种量6％,发酵周期60h。利用最佳培养基配方,在30℃,150r／min条件下发酵72h,工业级黄原胶产量达40.84g／L,发酵液粘度86000cp,丙酮含量4．1％,碳源转化率达68.1％。     

Xanthan production by Xanthomonas campestris using whey permeate medium

Xanthan gum is a polysaccharide that is widely used as stabilizer and thickener with many industrial applications in food industry. Our aim was to estimate the ability of Xanthomonas campestris ATCC 13951 for the production of xanthan gum by using whey as a growth medium, a by-product of dairy industry. X. campestris ATCC 13951 has been studied in batch cultures using a complex medium for the determination of the optimal concentration of glucose, galactose and lactose. In addition, whey was used under various treatment procedures (de-proteinated, partially hydrolyzed by β-lactamase and partially hydrolyzed and de-proteinated) as culture medium, to study the production of xanthan in a 2 l bioreactor with constant stirring and aeration. A production of 28 g/l was obtained when partially hydrolysed β-lactamase was used, which proved to be one of the highest xanthan gum production reported so far. At the same time, an effort has been made for the control and selection of the most appropriate procedure for the preservation of the strain and its use as inoculant in batch cultures, without loss of its viability and its capability of xanthan gum production. The pre-treatment of whey (whey permeate medium hydrolyzed, WPH) was very important for the production of xanthan by the strain X. campestris ATCC 13951 during batch culture conditions in a 2 l bioreactor. Preservation methods such as lyophilization, cryopreservation at various glycerol solution and temperatures have been examined. The results indicated that the best preservation method for the producing strain X. campestris ATCC 13951 was the lyophilization. Taking into account that whey permeate is a low cost by-product of the dairy industry, the production of xanthan achieved under the studied conditions was considered very promising for industrial application.     

Valorisation of chicken feathers for xanthan gum production using Xanthomonas campestris MO-03

Xanthan gum is an important commercial polysaccharide produced by Xanthomonas species. In this study, xanthan production was investigated using a local isolate of Xanthomonas campestris MO-03 in medium containing various concentrations of chicken feather peptone (CFP) as an enhancer substrate. CFP was produced with a chemical process and its chemical composition was determined. The addition of CFP (1–8?g/l) increased the conversion of sugar to xanthan gum in comparison with the control medium, which did not contain additional supplements. The highest xanthan production (24.45?g/l) was found at the 6?g/l CFP containing control medium in 54?h. This value was 1.73 fold higher than that of control medium (14.12?g/l). Moreover, addition of CFP improved the composition of xanthan gum; the pyruvate content of xanthan was 3.86% (w/w), higher than that of the control (2.2%, w/w). The xanthan gum yield was also influenced by the type of organic nitrogen sources. As a conclusion, CFP was found to be a suitable substrate for xanthan gum production.     

High production of xanthan gum by a glycerol-tolerant strain Xanthomonas campestris WXLB-006

The superior properties of xanthan gum make it an industrial aginomoto used in many industries, especially in oil recovery. In the present work, xanthan production from glycerol by a mutant strain Xanthomonas campestris WXLB-006 reached as high as 17.8?g/L in flask culture. With the adoption of pH control, varied aeration and agitation, and varied glycerol feeding strategy, xanthan production reached 33.9?g/L in a 7-L fermenter and fermentation time decreased to 60?hr. Instead of difficultly and costly purifying glycerol, this research provides a very good case for glycerol utilization. At the same time, this is the first report on a high glycerol-tolerant strain for microbial polysaccharide production and 33.9?g/L is the highest production of xanthan gum produced from glycerol so far.     

Biodegradation of xanthan by salt-tolerant aerobic microorganisms

Summary Three salt-tolerant bacteria which degraded xanthan were isolated from various water and soil samples collected from New Jersey, Illinois, and Louisiana. The mixed culture, HD1, contained aBacillus sp. which produced an inducible enzyme(s) having the highest extracellular xanthan-degrading activity found. Xanthan alone induced the observed xanthan-degrading activity. The optimum pH and temperature for cell growth were 5–7 and 30–35°C, respectively. The optimum temperature for activity of the xanthan-degrading enzyme(s) was 35–45°C, slightly higher than the optimum growth temperature. With a cell-free enzyme preparation, the optimum pH for the reduction of solution viscosity and for the release of reducing sugar groups were different (5 and 6, respectively), suggesting the involvement of more than one enzyme for these two reactions. Products of enzymatic xanthan degradation were identified as glucose, glucuronic acid, mannose, pyruvated mannose, acetylated mannose and unidentified oligo- and polysaccharides. The weight average molecular weight of xanthan samples shifted from 6.5·10⁶ down to 6.0·10⁴ during 18 h of incubation with the cell-free crude enzymes. The activity of the xanthan-degrading enzyme(s) was not influenced by the presence or absence of air or by the presence of Na₂S₂O₄ and low levels of biocides such as formaldehyde (25 ppm) and 2,2-dibromo-3-nitrilopropionamide (10 ppm). Formaldehyde at 50 ppm effectively inhibited growth of the xanthan degraders.     

A pyruvated mannose-specific xanthan lyase involved in xanthan degradation by Paenibacillus alginolyticus XL-1.

The xanthan-degrading bacterium Paenibacillus alginolyticus XL-1, isolated from soil, degrades approximately 28% of the xanthan molecule and appears to leave the backbone intact. Several xanthan-degrading enzymes were excreted during growth on xanthan, including xanthan lyase. Xanthan lyase production was induced by xanthan and inhibited by glucose and low-molecular-weight enzymatic degradation products from xanthan. A xanthan lyase with a molecular mass of 85 kDa and a pI of 7.9 was purified and characterized. The enzyme is specific for pyruvated mannosyl side chain residues and optimally active at pH 6.0 and 55 degrees C.     

Kinetic analysis of growth and xanthan gum production with Xanthomonas campestris on sucrose, using sequentially consumed nitrogen sources

A batch fermentation strategy using Xanthomonas campestris ATCC 13951 for xanthan gum production has been established in which all essential medium components are supplied at the onset. This has been achieved using sucrose as sole sugar feedstock. Sequential consumption of nitrogen sources (soybean hydrolysates, ammonium and nitrate salts) was observed to facilitate the further optimisation of the medium. Biomass accumulation was limited by phosphate availability. Xanthan yields of more than 60% (grams of xanthan per gram of sugar) have been obtained with constant acetyl content. However, pyruvyl substitution decreased as the growth rate declined, due to the metabolic constraints specific to phosphate depletion. High rates of carbon conversion into xanthan were observed throughout the culture and the ATP/ADP ratio was not affected by the decline in the specific growth rate.     

Isolation and characterization of a xanthan-degrading Microbacterium sp. strain XT11 from garden soil

AIMS: Isolation and characterization of the xanthan-degrading Microbacterium sp. XT11. METHODS AND RESULTS: The bacterial isolate XT11, capable of fragmenting xanthan, has been isolated from soil sample. Morphological and biochemical analyses, as well as 16S rRNA gene sequence comparisons, demonstrated that strain XT11 should be grouped in the genus Microbacterium, and represented a new member in this family. Xanthan could be degraded by the xanthan-degrading enzyme released from strain XT11. It has been shown that xantho-oligosaccharides fragmented from xanthan had both elicitor activity and antibacterial effect against Xanthomonas campestris pv. campestris. CONCLUSIONS: The xanthan-degrading enzyme produced by the newly isolated XT11 could fragment xanthan to form oligosaccharides. SIGNIFICANCE AND IMPACT OF THE STUDY: Xanthan-degrading products would be useful for potential application in the control of black rot of cruciferous plants caused by X. campestris pv. campestris and, as an oligosaccharide elicitor, in making these plants resistant to disease.     

Development of a phenomenological modeling approach for prediction of growth and xanthan gum production using Xanthomonas campestris

An unstructured kinetic model for xanthan production is described and fitted to experimental data obtained in a stirred batch reactor. The culture medium was composed of several nitrogen sources (soybean hydrolysates, ammonium and nitrate salts) consumed sequentially. The model proposed is able to describe this sequential consumption of nitrogen sources, the consumption of inorganic phosphate and carbon, the evolution of biomass, and production of xanthan. The parameter estimation has been performed by fitting the kinetic model in differential form to experimental data. Runs of the model for simulating xanthan gum production as a function of the initial concentration of inorganic phosphate have shown the positive effect of phosphate limitation on xanthan yield, though diminishing rates of production. The model was used to predict the kinetic parameters for a medium containing a 2-fold lower initial phosphate concentration. When tested experimentally, the measured fermentation parameters were in close agreement with the predicted model values, demonstrating the validity of the model.