Xanthan gum produced by Xanthomonas campestris from cheese whey: production optimisation and rheological characterisation

BACKGROUND: This aim of this study was the production and rheological characterisation of xanthan gum by Xanthomonas campestris pv. mangiferaeindicae IBSBF 1230 using industrial media and experimental design techniques in a bench bioreactor. RESULTS: The optimised conditions for the production of xanthan starting with 900 mL of cheese whey were 1 g L^?1 magnesium sulphate, 20 g L^?1 potassium phosphate, 28 °C temperature and initial pH 7.2 at 390 rpm agitation and 1.5 vvm aeration, resulting in 36 g L^?1 gum in 72 h. The highest viscosity obtained in the production optimisation study was 1831.34 mPa s at 25 °C with 30 g L^?1 gum. The use of CaCl₂ resulted in the highest solution viscosity under conditions of 25 °C, 1 g L^?1 salt and 46.8 g L^?1 gum, with a value of 1704.53 mPa s. CONCLUSION: In this study, cheese whey, a by‐product of the dairy industry, was used as substrate in the production of xanthan gum, a valuable product in food applications, with optimised high gum production in a bioreactor and a wide range of viscosity values. Copyright © 2009 Society of Chemical Industry     

一株野油菜黄单胞菌产黄原胶的性质

通过发酵一株野油菜黄单胞菌得到黄原胶,进而测定该黄原胶在不同质量浓度、pH值、氯化钠质量浓度、温度下黏度变化,分析黄原胶流变特性、丙酮酸质量分数和黏均分子质量。结果表明：本实验菌株的黄原胶产量达到28.4 g/L,黄原胶黏度在质量浓度高于4.0 g/L时迅速升高,黄原胶黏度在pH 3.0～10.0之间稳定。氯化钠质量浓度由10 g/L增加到70 g/L时,使1.0 g/L黄原胶黏度提高20%,而温度高于35 ℃时使1.0 g/L黄原胶黏度降低。黄原胶的丙酮酸质量分数达到6.35%,黏均分子质量为5.7×106 D。1.0 g/L黄原胶的稠度系数和流体指数分别为26.94和0.765 5,5.0 g/L黄原胶的稠度系数和流体指数分别为489.65和0.328 1。研究表明该株野油菜黄单胞菌具有较大的潜在应用价值。     

黄原胶寡糖对野油菜黄单胞菌的抑菌性能研究

碱性条件下对黄原胶进行氧化降解,透析得到三种黄原胶寡糖（XGO-A,XGO-B和XGO-C）,对产物进行FT-IR表征,GPC法测定其分子量分别为3600、7500和10100。三种黄原胶寡糖的丙酮酸含量分别为5.7%、5.3%和4.8%;还原糖含量分别为23.7%、22.5%和21.1%。采用琼脂平板打孔法、最低抑菌浓度以及生长曲线方法,考察了三种黄原胶寡糖对野油菜黄单胞菌的抑菌能力;同时检测了三种寡糖对野油菜黄单胞菌细胞膜通透性的影响。结果表明,分子量为7500的XGO-B具有更好的抑菌性能。而当丙酮酸和还原糖含量相近时,对野油菜黄单胞菌的抑菌性能可能与黄原胶寡糖的分子量有关;随着分子量的上升,寡糖对野油菜黄单胞菌细胞膜破坏增强,这表明破坏细胞膜通透性是抑菌机理之一。      

Xantho mo nas campestris-9002源黄原胶发酵动力学的研究

利用恒化培养技术研究了黄原胶发酵动力学,建立了较为合理的恒化培养系统。对采集的数据用计算机进行回归,求得最大比生产速率μmax=0.242h-1,饱和常数Ks=41.32,基质得率系数YGmax=1.560g/g以及维持系数m=0.009g/g·h,最佳理论稀释速率Dm=0.05428h-1。并研究了黄原胶比生成速率、细胞产素、残糖、粘度等参数随菌体比生成速率的变化关系。     

黄原胶的结构与复配性质研究

黄原胶是一种用途非常广的食品增稠剂,并且与其他的食品添加剂有很好的复配效应,本文综述了黄原胶的结构与性质,黄原胶与魔芋胶、槐豆胶、瓜尔豆胶、结冷胶、琼脂单体的复配以及黄原胶与两种及两种以上食品增稠剂的复配应用研究。复配产生了良好的协同增效,协同凝胶效应,也使得食品稳定性大大提高,凝胶性由脆到富有弹性的任意转变。     

Xanthan gum production under different operational conditions by <Emphasis Type="Italic">Xanthomonas axonopodis</Emphasis> pv <Emphasis Type="Italic">vesicatoria</Emphasis> isolated from pepper plant

The influence of operational conditions (pH, stirrer speed, and temperature) used in the process of xanthan production by Xanthomonas axonopodis pv vesicatoria (XCVA3-1) isolated from pepper plant were evaluated through yield of xanthan and compared with control strain Xanthomonas campestris NRRL-B 1459. Different conditions used during the fermentation affected the xanthan production. In this study the best combination of yield was obtained, reaching 1.325 g/100 mL with the use of pH 7.0, 30°C, and 250 rpm during fermentation. Increased yield of xanthan production can be obtained at high agitation values, with the maximum at 400 rpm. Higher yields of gum production can be obtained at 30°C and the optimum pH was found 7.0. This results were similar for the X. campestris NRRL-B 1459.     

A Taxonomic Study of Staphylococcus spp. Isolated from Fermented Sausages

Computer assisted numerical analysis was done on 182 characters for each of 107 strains, including 79 Gram-positive, catalase-positive, facultatively anaerobic cocci from 14 different types of fermented sausage offered for retail sale in the UK. The majority of meat isolates was identified with Staphylococcus xylosus (38%), saprophyticus (29%) or warneri (10%); eight isolates were left unassigned to a species. The identification matrix derived from these data provided the basis for objective differentiation of isolates from fermented meats.     

Development of Molecular Typing Methods for Bacillus spp. and Paenibacillus spp. Isolated from Fluid Milk Products

Bacillus spp. and related sporeformers are important food spoilage organisms. While use of molecular subtyping methods has provided important information on the ecology and transmission of foodborne pathogens, the lack of rapid, reliable, and affordable subtyping methods for Bacillus spp. has limited our ability to understand and control their transmission throughout the food chain. We used a previously described collection of Bacillus spp. and Paenibacillus spp. isolated from dairy products to develop a DNA sequencing‐based subtyping approach for these spoilage microorganisms. After optimization of polymerase chain reaction (PCR) parameters, primers targeting the rpoB housekeeping gene allowed for successful amplification in all isolates. rpoB sequencing allowed differentiation of 29 subtypes (that is, sequence types) among the 57 isolates characterized. Phylogenetic analyses of rpoB sequences revealed distinct monophyletic lineages that correlated with bacterial genera (Bacillus and Paenibacillus) as well as with species or species‐like assemblages within each genus. rpoB sequencing provided improved subtype discrimination over 16S rDNA sequencing; therefore, rpoB sequencing allows for both sensitive subtype discrimination as well as for species and genus identification. Analysis of subtypes isolated over time in dairy products revealed the presence of both persistent and transient bacterial subtypes, indicating that application of these methods can improve our understanding of the ecology of these spoilage organisms and can help in identification of bacterial niches that may contribute to the persistence of these spoilage organisms in food systems.     

野油菜黄单胞菌源黄原胶基因工程研究进展

黄原胶在许多行业中得到广泛的应用,是具有重大商业价值的微生物多糖。随着基因工程技术的迅速发展,针对黄原胶产率的研究也由菌种选育、培养基、发酵条件等转向基础代谢流、基因工程和酶工程方面的研究。国内外已有基础代谢流、酶工程、基因工程方面基础的研究报道,并且也取得了一定的成果。     

黄原胶的流变特性及其在食品工业中的应用

黄原胶是一种广泛应用与食品、化工等领域的微生物多糖,本论文主要论述了黄原胶的分子结构、流变性质及其在食品工业中的应用.     

降低冰核生产菌X．ampelina TS206黄原胶产率的研究

培养基中不同的碳源影响冰核细菌的冰核活性、生物量和产胶率，麦芽糖、山梨醇、蔗糖等均可做为促进冰核细菌生长碳源，麦芽糖作为碳源加入发酵培养基中生物活性和生物量均较高，同时产胶率低于葡萄糖和蔗糖十倍左右。麦芽汁代替麦芽糖可以降低产胶率，但效果不如麦芽糖。在培养基中加入0．1ml，100ml乳酸可以有效地抑制黄原胶的产生，而对冰核活性和生物量影响不大。     

培养条件对冰核生产菌Xanthomonas ampelina TS206产胶率的影响

培养条件影响冰核细菌的生物量、冰核活性和产胶率。通过单因子试验确定了TS206的最适培养条件：最适装液量为100ml，培养基的最适起始pH值为7．0，最佳培养时间为48h，但是通过上述培养条件的调整并不能明显降低黄原胶的产率。采取从30℃到J18℃的双温培养可以在保持较高的生物量和冰核活性的前提下，降低黄原胶的产量，并明显缩短了培养时间。     

培养基组成对冰核生产菌Xanthomonas ampelina TS206产胶率的影响

培养基中不同的碳源、氮源和无机盐影响冰核细菌的生长、冰核蛋白的表达及黄原胶的产率。蔗糖、麦芽糖和山梨醇均有利于冰核蛋白的生产,而且麦芽糖和山梨醇的产胶率要明显低于其它碳源;蛋白胨和玉米浆均可以作为冰核蛋白生产的优良氮源使用,无机氮不适合作为唯一氮源使用,但适量的KNO3和蛋白胨结合使用时,可以促进菌体的生长和冰核活性的表达,但同时也促进了黄原胶的形成;适量地添加无机盐对菌体的生长和冰核活性的表达有一定的促进作用,对黄原胶的合成没有明显的抑制作用。     

甘蓝黑腐病黄单胞菌胞膜离子通道透性对黄原胶生物合成的影响

本文研究了K+,Na+离子浓度改变对甘蓝黑腐病黄单胞菌(Xanthomonascampestris)胞膜离子通道透性的影响。通过发酵过程采样点电子显微镜照片的软件分析和后期数据的统计处理分析,结合电镜照片,源用胞膜基本理论,阐述了甘蓝黑腐病黄单胞菌(Xanthomonascampestris)胞膜离子通透的透性对黄原胶生物合成的影响。结果表明,胞膜通道的透性对黄原胶合成前体物质的运输有极其重要的影响。     

一株产高黏度耐酸性黄原胶生产菌的选育及其发酵工艺研究

选用黄原胶生产菌株野油菜黄单胞杆菌XG30-18,经微波辐射后再经亚硝基胍(NTG)处理筛选出一株产高黏度耐酸性黄原胶的突变菌株MW-42-NTG-6,并对其发酵条件进行初步筛选。确定其培养基以蔗糖和玉米淀粉做为混合碳源、大豆分离蛋白为氮源。通过正交试验确定最适发酵条件为接种量8%、转速240r/min、pH7.0、培养温度28℃。在此发酵条件下,产胶率最高可达到3.92%、黏度为1790cP、耐酸性测定1%黄原胶溶液pH值为4.2。     

木霉菌株利用作物秸秆产油脂研究进展

木霉能分泌产生纤维素酶、木聚糖酶和木质素酶,并能产生和积累微生物油脂,因此利用木霉能够分解木质纤维素类的作物秸秆,并利用分解木质纤维素产生的单糖、合成和积累油脂.该文介绍了微生物分解秸秆产油的意义,综述了木霉菌作为发酵秸秆产生微生物油脂的研究对象优势和利用木霉生产微生物油脂的研究现状及进展.     

Molecular characterization and antibiotic resistance of Staphylococcus spp. isolated from cheese processing plants

The aim of this research paper was to characterize coagulase-positive and coagulase-negative staphylococci from raw milk, Minas cheese, and production lines of Minas cheese processing. One hundred isolates from 3 different cheese producers were characterized using molecular approaches, such as PCR, molecular typing, and DNA sequencing. Staphylococcus aureus (88% of the isolates) was the most abundant followed by Staphylococcus epidermidis, Staphylococcus hyicus, and Staphylococcus warneri. Among the 22 enterotoxin genes tested, the most frequent was seh (62% of the isolates), followed by selx and ser. Hemolysin genes were widely distributed across isolates, and Panton-Valentine leukocidin and toxic shock syndrome toxin genes were also identified. Methicillin-resistant S. aureus were staphylococcal cassette chromosome mec III, IVa, IVd, and others nontypeable. In the phenotypic antibiotic resistance, multiresistant isolates were detected and resistance to penicillin was the most observed. Using spa typing, we identified several types and described a new one, t14969, isolated from cheese. These findings suggest that antibiotic resistance and potentially virulent strains from different sources can be found in the Brazilian dairy processing environment. Further research should be conducted with collaboration from regulatory agencies to develop programs of prevention of virulent and resistant strain dissemination in dairy products and the processing environment.     

Xanthan Production by Mutant Strain of Xanthomonas campestris TISTR 840 in Raw Cassava Starch Medium

Raw cassava starch was used as carbon source in growing Xanthomonas campestris TISTR 840 for xanthan production due to its cheap price and mass production in Thailand. However, xanthan production with raw cassava starch yielded low content (4.31 g/l). A low level of amylase was detected in the XOL medium of X. campestris when raw cassava starch was used. Treatment of X. campestris TISTR 840 with ethyl methansulfonate resulted in the isolation of Xc-M, a strain that showed highest amylase overproduction. When cultured in bioreactor with a medium containing raw cassava starch, the growth of Xc-M cells was significantly higher than that of the wild type. The mutant produced 3.46- and 1.39-fold increased amylase activity and xanthan yield, respectively. Xc-M is useful for xanthan production in media containing raw starch as a carbon source.     

xanK单位点突变对野油菜黄单胞菌菌黄素合成及黄原胶产物性质的影响

菌黄素的存在使得野油菜黄单胞菌产生的黄原胶发酵液呈现黄色,并显著影响了黄原胶的性状、产量及提取工艺。研究过程中得到一株自然突变的不产生菌黄素的黄原胶生产菌株XW,测序发现该菌株xanK基因的一处碱基突变使相应编码的天冬氨酸突变为甘氨酸。为探究xanK基因突变对菌黄素合成的影响,通过回补试验将野生型菌株的xanK基因导入到突变菌株中,发现突变菌株的菌黄素合成恢复,说明该突变导致菌黄素合成受阻。此外,对两种黄原胶产物进行分析,结果显示突变菌株产生的黄原胶在黏度和丙酮酸含量上均高于野生型菌株,而分子量和乙酰基含量要低于野生型菌株,说明菌黄素对黄原胶的合成可能具有复杂的影响。     

黄原胶协同干热变性对紫薯淀粉特性的影响

为开发强度高、透明度好且阻水能力优的可食性淀粉膜,本试验添加黄原胶对紫薯淀粉进行干热变性处理,研究其产物特性的变化。结果表明:黄原胶协同干热变性处理后的紫薯淀粉颗粒略微膨胀,大小不均一且发生粘连现象;糊化起始温度略有降低,峰值黏度与终值黏度均升高,热稳定性提高;淀粉糊的冻融稳定性显著提高,溶解度和膨胀度降低,且透明度有所降低;淀粉糊的流变曲线表现为逆时针环状,屈服应力明显增大,其形成的凝胶呈现固体特征,储能模量G'增加,剪切结构恢复力显著提高;淀粉属C-型晶体,干热处理前后淀粉的X-射线衍射图谱无明显变化,但干热变性处理使淀粉结晶度增大。因此,添加黄原胶对紫薯淀粉进行干热变性,可使产物的特性发生明显改变。