Conversion of chitinous wastes to hydrogen gas by Clostridium paraputrificum M-21

The chitinolytic bacterium Clostridium paraputrificum strain M-21 produced 2.2 and 1.5 mol hydrogen gas from 1 mol N-acetyl-D-glucosamine (GlcNAc) and ball-milled chitin equivalent to 1 mol of GlcNAc, respectively, at pH 6.0. In addition, strain M-21 efficiently degraded and fermented ball-milled raw shrimp and lobster shells to produce hydrogen gas: 11.4 mmol H2 from 2.6 g of the former and 7.8 mmol H2 from 1.5 g of the latter. Hydrogen evolution from these shell wastes were enhanced two fold by employing acid and alkali pretreatment. Waste from the starch industry was also converted to hydrogen. When C. paraputrificum M-21 was cultivated on ball-milled chitin and ball-milled shrimp shells for 14 and 12 h, respectively, chitinases ChiA and/or ChiB were detected as the major chitinase species in the supernatant of the cultures, suggesting that the play a critical role in the degradation of chitinous materials.     

A new type of beta-N-Acetylglucosaminidase from hydrogen-producing Clostridium paraputrificum M-21

A beta-N-acetylglucosaminidase gene (nag84A) was cloned from Clostridium paraputrificum M-21 in Escherichia coli. The nag84A gene consists of an open reading frame of 4647 by encoding 1549 amino acids, with a deduced molecular weight of 174,311, which have a catalytic domain belonging to family 84 of the glycoside hydrolases. Nag84A was purified from a recombinant E. coli and characterized. Although Nag84A exhibited high homology to the hyaluronidase from Clostridium perfringens, it did not degrade hyluronic acid. The enzyme hydrolyzed chitooligomers such as di-, tri-, tetra-, penta- and hexa-N-acetylchitohexaose, and synthetic substrates such as 4-methylumbelliferyl N-acetyl beta-D-glucosaminide [4-MU-(G1cNAc)], but did not hydrolyze 4-MU-beta-D-glucoside, 4-MU-alpha-D-glycoside, 4-MU-alpha-D-GlcNAc, 4-MU-alpha-D-galactoside, 4-MU-beta-D-xyloside, PNP-beta-D-galactoside, and PNP-alpha-D-xyloside. The enzyme was optimally active at 50 degrees C and pH 6.5, and the apparent K(m) and V(max) values for 4-MU-(GlcNAc) were 8.5 microM and 1.39 micromol/min/mg of protein, respectively. SDS-PAGE, zymogram, and immunological analyses suggested that Nag84A was inducible by ball-milled chitin. Since Nag84A has a high molecular weight with a family 84 catalytic domain with high homology to hyaluronidases but no hyaluronidase activity, the enzyme is a novel beta-N-acetylglucosaminidase different from others reported having low molecular weights and belonging to family 3 and family 18.     

Influence of different dietary regimens upon the composition of the human fecal flora

The composition of the fecal flora in two groups of children in primary school age with (a) normal, ad libitum diet (school-group, 20 children), and (b) lacto-ovo-vegetarian diet (Salem-group, 20 children) was examined. Fecal analysis was concentrated upon the isolation of the main anaerobic and aerobic microorganisms. The pattern of S-, M-, and R-forms of Enterobacteriaceae with special regard to E. coli was investigated additionally. In the school-group counts of Clostridium species, R-, and M- forms of E. coli were significantly higher than in the Salem-group. The numbers of Bifidobacterium, Actinomyces, and Enterobacteriaceae species, as well as S-forms of E. coli were significantly increased in the Salem-group, as compared to the school-children. The data reveal a relationship between the occurrence of different anaerobic species and the SMR-pattern of E. coli, with Clostridium species in particular. The SMR-pattern of E. coli may reflect conditions of intestinal metabolism and mucosal immunity. It may serve as a simple parameter in routine examination of fecal specimen.     

Characterization of Clostridium paraputrificum chitinase A from a recombinant Escherichia coli

Clostridium paraputrificum chitinase A (ChiA) was purified from a recombinant Escherichia coli. ChiA was active toward chitin from crab shells, colloidal chitin, glycol chitin, and 4-methylumbelliferyl beta-D-N,N'-diacetylchitobioside [4-MU-(GlcNAc)2]. ChiA showed maximum activity at pH 6.0 and its optimum temperature was 45 degrees C. ChiA was stable between pH 6.0 and 9.0 and at temperatures up to 40 degrees C. The K(m) and V(max) values of ChiA for 4-MU-(GlcNAc)2 were estimated to be 6.9 microM and 43 micromol/min/mg, respectively. Thin-layer chromatography indicated that ChiA hydrolyzes chitooligosaccharides to mainly chitobiose. ChiA was found to adsorb not only chitinous polymers but also cellulosic polymers.     

Characterization of N-acetylmuramidase M-1 of Streptomyces globisporus produced by Escherichia coli BL21(DE3)pLysS

A gene of Streptomyces globisporus encoding N-acetylmuramidase M-1 was cloned into the pET26b vector and expressed in Escherichia coli BL21(DE3)pLysS. Maximal activity for the purified enzyme was observed at 55 degrees C with an optimal pH of 5.3, and N-bromosuccinimide strongly inhibited lytic activity even at a concentration of 0.01 mM. The enzyme showed N,O-diacetylmuramidase activity.     

Clostridium bolteae ATCC BAA-613 D-塔格糖3-差向异构酶的诱导表达、纯化及活性研究

D-塔格糖3-差向异构酶是生物法生产新型功能性因子D-阿洛酮糖最为有效的酶。一种新型的能够编码D-塔格糖3-差向异构酶的基因CLOBOL₀0069被克隆,它来源于Clostridium bolteae ATCC BAA-613。以pUC57为克隆载体,以pET-22b（+）为载体质粒,E.coli BL21（DE3）为宿主细胞,构建了基因重组工程菌。IPTG诱导剂诱导目的蛋白的表达;通过镍柱亲和层析,杂蛋白与目的蛋白得到了很好的分离。对纯化的重组蛋白样品进行SDS-PAGE分析,在约32ku处出现明显的特征条带。通过活性研究表明,Clostridium bolteae ATCC BAA-613 DTEase属于DTEase家族,并具有较高的生物转化率,反应10h后转化率达到20%。     

渗透压诱导表达重组Clostridium thermosulfurogenes β-淀粉酶基因

以热硫梭菌Clostridium thermosulfurogenes基因组为模板,PCR扩增出β-淀粉酶基因;将该基因克隆到pET-22b(+)载体上,转入大肠杆菌BL21-SI,采用NaCl形成的高渗透压诱导表达。研究了不同诱导条件对重组菌产β-淀粉酶的影响,结果以菌体密度达到OD600为0.6,诱导剂NaCl浓度为0.6 mol/L,诱导温度为35℃最佳。重组菌以LBON为培养基分批发酵时,由于营养限制,菌体密度OD600仅为4.60,β-淀粉酶活力为118U/mL。采用pH-Stat分批补料发酵时,在菌体密度仅是分批发酵的2.35倍的条件下,得到6.12倍的产酶量,酶活力达722U/mL。重组β-淀粉酶70℃水解可溶性淀粉3h的麦芽糖转化率为62.2%,高于大麦β-淀粉酶的转化率。     

Combined effects of mustard flour,acetic acid,and salt against Esherichia coil O157:H7 stored at 5 and 22 degrees C

The combined effects of acetic acid and mustard flour were investigated to ascertain their impact on Escherichia coli O157:H7 stored at 5 and 22 degrees C. Samples were prepared with various concentrations of acetic acid (0, 0.25, 0.5, 0.75, and 1% [vol/vol]) combined with 10% (wt/vol) Baltimore or Coleman mustard flour and 2% (fixed; wt/vol) sodium chloride. An acid-adapted mixture of three E. coli O157:H7 strains (10(6) to 10(7) CFU/ml) was inoculated into prepared mustard samples that were stored at 5 and 22 degrees C, and samples were assayed periodically for the survival of E. coli O157:H7. The numbers of E. coli O157:H7 were reduced much more rapidly at 22 degrees C than at 5 degrees C. E. coli O157:H7 was rapidly reduced to below the detection limit (<0.3 log10, CFU/ml) after 1 day at 22 degrees C, whereas it survived for up to 5 days at 5 degrees C. There was no synergistic or additive effect with regard to the killing of E. coli O157:H7 with the addition of small amounts of acetic acid to the mustard flour. When stored at 5 degrees C, mustard in combination with 0.25 (M-0.25), 0.5 (M-0.5), and 0.75% (M-0.75) acetic acid exerted less antimicrobial activity than the control (M-0). The order of lethality at 5 degrees C was generally M-0.25 = M-0.5 < M-0.75 = M-0 < M-1. The addition of small amounts of acetic acid (<0.75%) to mustard retards the reduction of E coli O157:H7. Statistical reduction in populations of E. coli O157:H7 (P < 0.05) was enhanced relative to that of the control (mustard alone) only with the addition of 1% acetic acid. This information may help mustard manufacturers to understand the antimicrobial activity associated with use of mustard flour in combination with acetic acid.     

产抗菌蛋白芽孢杆菌R21-4的鉴定及其抗菌谱研究

筛选的芽孢杆菌R21-4对某些革兰氏阳性、革兰氏阴性细菌及真菌均有抑制作用,具有较广的抑菌谱,特别是对食品中的常见腐败菌,如蜡样芽孢杆菌、大肠杆菌、产气荚膜杆菌、产气肠杆菌、荧光假单胞菌等均有明显抗菌效果。在对其进行生理生化以及16Sr RNA基因序列测定和聚类分析软件的分析后,鉴定菌株R21-4为枯草芽孢杆菌Bacillus subtilissp.R21-4,并采用琼脂块法和生长曲线法对其抗菌机理进行了研究。     

Clostridium scindens ATCC35704中的D-塔格糖-3-差向异构酶的克隆表达、纯化及活性研究

D-阿洛酮糖作为一种新型低热量功能性甜味剂,可以通过D-塔格糖-3-差向异构酶家族,以D-果糖为底物C-3位异构化得到。一个新的来源于微生物Clostridium scindens ATCC 35704中ZP 0243228的D-塔格糖-3-差向异构酶基因(CS-DTE),通过克隆并成功导入E.coli BL21(DE3)中,构建了基因重组菌,诱导目的重组基因过量表达;经亲和层析纯化的重组蛋白样品进行SDS-PAGE分析,在约31 ku处出现显著的特征蛋白条带;通过对其活性检测表明,该重组酶分别以D-塔格糖和D-果糖为底物,可以生成D-山梨糖和D-阿洛酮糖,转化率分别为8.6%和27.9%。     

丝氨酸羟甲基转移酶基因的功能表达及其活性鉴定

从大肠杆菌染色体DNA中成功克隆到丝氨酸羟甲基转移酶基因 ,并将其插入表达载体 pET15b中 ,在大肠杆菌中得到了高表达。基因互补实验鉴定了其活性     

Identification and characterization of Clostridium paraputrificum M-21, a chitinolytic, mesophilic and hydrogen-producing bacterium

A strictly anaerobic, mesophilic and chitinolytic bacterial strain, M-21, was isolated from a soil sample collected from Mie University campus and identified as Clostridium paraputrificum based on morphological and physiological characteristics, and 16S rRNA sequence analysis. C. paraputrificum M-21 utilized chitin and N-acetyl- -glucosamine (GlcNAc), a constituent monosaccharide of chitin, to produce a large amount of gas along with acetic acid and propionic acid as major fermentation products. Hydrogen and carbon dioxide accounted for 65% and 35% of the gas evolved, respectively. The conditions for 1 l batch culture of C. paraputrificum, including pH of the medium, incubation temperature and agitation speed, were optimized for hydrogen production with GlcNAc as the carbon source. The bacterium grew rapidly on GlcNAc with a doubling time of around 30 min, and produced hydrogen gas with a yield of 1.9 mol H₂/mol GlcNAc under the following cultivation conditions: initial medium pH of 6.5, incubation temperature of 45°C, agitation speed of 250 rpm, and working volume of 50% of the fermentor. The dry cell weight harvested from this culture was 2.0 g/l.     

Clostridium cellulolyticum D-塔格糖3-差向异构酶基因的克隆、表达及酶活性

D-塔格糖3-差向异构酶是生物法生产新型功能性因子D-阿洛酮糖最为有效的酶。作者克隆到一种新型的D-塔格糖3-差向异构酶基因,来源于微生物Clostridium cellulolyticumH10。以pET-22b(+)为载体质粒,E.coliBL21(DE3)为宿主细胞,构建了基因重组菌,IPTG可诱导目的蛋白质的过量表达;经亲和层析纯化的重组蛋白质样品进行SDS-PAGE分析,在约31 000处出现显著的特征蛋白质条带;活性检测结果表明:该重组酶具有较高的转化活性。     

带有突变穿膜肽重组凋亡素可溶性表达的研究

目的构建apoptin（凋亡素）-HBDCK-pET28a突变体重组表达载体,在大肠杆菌BL21（DE3）中实现高效可溶性表达,并观察突变后穿膜肽（CPP）在HeLa细胞中的转导活性。方法采用PCR介导突变方法将重组蛋白apoptin-HBD及EGFP-HBD的HBD结构域中的Cys（C）突变为Lys（K）。突变的重组质粒在大肠杆菌BL21（DE3）中表达,Ni2＋-NTA亲和层析纯化目的蛋白,进一步观察HeLa细胞突变后HBD的转导活性。结果经双酶切鉴定和序列分析,突变后的重组质粒apoptin-HBDCK-pET28a及EGFP-HBDCK-pET28a构建正确。转化E.coli BL21（DE3）后,融合蛋白均获得可溶性表达。EGFP-HBDCK作用于HeLa细胞13 h后,可观察到细胞内强绿色荧光。结论 HBD结构域中C突变为K,可达到融合蛋白可溶性表达的目的,且仍能保持很强的转导活性,可携带EGFP蛋白进入HeLa细胞。     

细菌透明质酸酶基因工程菌的构建及高效表达

目的将兽疫链球菌透明质酸酶hyl基因在大肠杆菌原核表达系统中高效分泌表达。方法通过PCR方法扩增得兽疫链球菌hyl基因,Xho I和Nco I双酶切后,连入表达载体pET26b(+),并转化入大肠杆菌,经低温异丙基-β-D-硫代半乳糖苷或乳糖诱导表达,DNS法检测胞外透明质酸酶活性。结果成功构建含兽疫链球菌透明质酸酶基因hyl的大肠杆菌基因工程菌株,经IPTG诱导并添加甘氨酸后胞外透明质酸酶活性高达5.3×104 U/mL。结论实现了透明质酸酶在原核系统中的表达,为工业化生产奠定了基础,具有很好的市场前景。     

Detection of Clostridium perfringens type A enterotoxin in faecal and food samples using immunomagnetic separation (IMS)-ELISA

A simple, rapid and sensitive immunoassay, based on immunomagnetic particles (Dynabeads M-280) was developed for detection and quantitation of Clostridium perfringens type A enterotoxin from faecal and food extracts. The assay had a detection limit of 2.5 ng/ml enterotoxin in homogenates of faeces and inoculated meat extracts. The specificity was confirmed by both crossed immunoelectrophoresis and Western immunoblotting techniques, using a purified enterotoxin as standard.     

基于ELISA克罗诺杆菌单链抗体制备与鉴定

利用基因工程技术制备克罗诺杆菌特异性单链抗体(sc Fv)。从克罗诺杆菌单克隆抗体的杂交瘤细胞中提取总RNA,利用RT-PCR反转录合成第一链c DNA后再扩增出抗体的重链可变区(VH)和轻链变区(VL)基因片段,采用重叠延伸PCR的方法,用柔性多肽Linker接头(Gly4Ser)3将VH基因和VL基因拼接成sc Fv基因片段,XhoⅠ﹑Eco RⅠ限制性内切酶双酶切sc Fv后克隆到原核表达载体p ET-26b中构建重组质粒sc Fv-pet-26b,挑取阳性克隆提取重组质粒后转入大肠杆菌BL21中进行诱导表达,通过His柱进行亲和层析,最后利用ELISA检测单链抗体的活性。成功构建了表达克罗诺杆菌单链抗体的基因工程菌株,通过SDS-PAGE和ELISA试验结果表明,诱导表达的罗诺杆菌单链抗体分子量约为30 k Da,其能与罗诺杆菌特异性结合,可作为免疫检测罗诺杆菌的候选抗体分子。     

丝胶抗冻肽在大肠杆菌中的重组表达及其抗冻活性初探

为了高效制备抗冻肽,研究一种丝胶抗冻肽目的基因SerD在大肠杆菌BL21菌株中的重组表达,并分析表达产物的抗冻活性。首先合成SerD基因片段,经KpnI和XhoI双酶切后定向插入质粒载体Pet32a中,构建表达质粒Pet32a-SerD,然后电转化入大肠杆菌BL21(DE3),在IPTG诱导下进行目的基因表达,利用镍琼脂糖亲和层析对目的重组蛋白进行纯化,并对其进行抗冻活性分析。结果表明,最佳表达条件为重组菌在20℃诱导16 h;通过十二烷基硫酸钠聚丙烯酰胺凝胶电泳(Sodium Dodecyl Sulphate-PolyAcrylamide Gel Electrophoresis,SDS-PAGE)和蛋白质免疫印迹试验(Western-Blot)鉴定重组蛋白表达成功且His-SerD融合蛋白表达的分子量在25~35 kDa之间;胞内表达His-SerD融合蛋白的大肠杆菌BL21-SerD复苏后的生长活性明显高于PBL空载菌;添加His-SerD融合蛋白可明显降低溶液中冰晶颗粒大小,具有较好的重结晶抑制效果。本文通过基因工程方法在大肠杆菌中成功构建丝胶肽抗冻肽的重组表达系统,并最终获得具有抗冷冻胁迫保护作用的His-SerD融合蛋白。     

嗜碱耐盐芽孢杆菌乙醛脱氢酶基因aldC的克隆及组氨酸融合酶蛋白的表达

应用PCR扩增嗜碱耐盐芽孢杆菌乙醛脱氢酶基因aldC,重组至原核表达载体pET30b（＋）,转化大肠杆菌BL21（DE3）,诱导表达的重组乙醛脱氢酶在碳端含有一个组氨酸标签。SDS-PAGE考察蛋白的表达量和亚基分子量,并对Km值进行了考察。成功构建了pET30b-aldC原核表达质粒;诱导表达了亚基分子量约为56 kDa的组氨酸融合蛋白;乙醛脱氢酶活性比对照菌增加了约3.5倍;Km值为2.874 mmol/L。成功克隆并诱导表达了含组氨酸标签的嗜碱耐盐芽孢杆菌乙醛脱氢酶基因aldC。     

Nisin-rbLF-N融合基因的构建及其在大肠杆菌中的表达

针对乳链菌肽(nisin)抑菌谱窄的缺点,选择对抗菌谱较广且具有较强抗性的牛乳铁蛋白氨基末端多肽(rbLF-N)为材料,构建融合基因Nisin-rbLF-N。将融合基因克隆到原核表达载体pGEX-4T1 中,转化E. coli BL21(DE3)进行诱导表达,将诱导表达的产物进行Tricine-SDS-PAGE 蛋白电泳及抑菌活性检测。结果表明,克隆菌经诱导后可表达出可观的融合蛋白,融合蛋白以包涵体形式存在,包涵体经洗涤、尿素溶解、复性后具有抗菌生物活性。