Enhanced secreting expression and improved properties of a recombinant alkaline endoglucanase cloned in <Emphasis Type="Italic">Escherichia coli</Emphasis>

An alkaline endoglucanase from Bacillus akibai III-3A was successfully expressed in Escherichia coli in active form, and secretion was greatly enhanced by addition of 5 g/l ethylenediamine tetraacetic acid (EDTA) to the culture medium at the induction time of 12 h. Under the optimal culture conditions, extracellular and total endoglucanase activities were 18.5 and 31.2 U/ml, respectively. Both the recombinant and native enzymes exhibited similar properties with respect to broad pH stability, good thermostability, and resistibility to various metal ions and reagents examined. However, unlike the native endoglucanase that was partly inhibited by sodium dodecyl sulfate (SDS), the recombinant enzyme had good resistibility to SDS, being very stable in the commercial detergents, and no decrease in residual activity was observed in 0.2% (w/v) laundry detergent, indicating that it was suitable for application in detergents industry.     

过表达TatAdCd转位酶对枯草芽孢杆菌脂肪酶分泌的影响

【目的】研究过表达枯草芽孢杆菌Tat运输途径的Tat Ad Cd转位酶对促进脂肪酶分泌的影响。【方法】用cdd基因的串联启动子和前导区,替换tat AD-CD操纵子的启动子和前导区,并在染色体sac B基因位点整合表达;采用q RT-PCR方法表征tat AD-CD操纵子的表达水平;用脂肪酶表达质粒p HP13L转化Tat Ad Cd转位酶过表达菌株,构建产脂肪酶重组菌。通过测定脂肪酶活性,以及聚丙烯酰胺凝胶电泳,考察Tat Ad Cd转位酶过表达对脂肪酶分泌的影响。【结果】tat AD-CD操纵子被过表达,其胞内m RNA相对水平提高了185倍。Tat Ad Cd转位酶的过表达,使脂肪酶发酵单位提高了40%。【结论】使用cdd基因的串联启动子和前导区,能够有效地过表达目的基因;枯草芽孢杆菌脂肪酶可以同时经由Sec途径和Tat途径分泌;过表达Tat Ad Cd转位酶,能够显著提高脂肪酶的分泌量。     

Expression and secretion of carboxymethyl cellulase in Bacillus subtilis by Lactobacillus casei lactate dehydrogenase gene promoter

The secretion ability of the signal peptide of carboxymethyl cellulase (CMCase) was combined with the high expression ability of the Lactobacillus casei lactate dehydrogenase gene (ldh) promoter sequence (P) in Bacillus subtilis RM125. The CMCase was successfully secreted to the culture medium and the enzyme activity by P (11.2 U/ml) was approximately 4 fold higher than by its own promoter (2.7 U/ml).     

双功能枯草杆菌诱导型高效表达分泌载体的构建与鉴定

利用大肠杆菌质粒pSP72和枯草杆菌质粒pUB18共整合得到双功能克隆载体pSB。在pSB多克隆位点依次引入枯草杆菌果聚糖蔗糖酶基因启动子-信号肽序列sacBp.s.、地衣芽孢杆菌淀粉酶基因终止子序列α-amyT和短小芽孢杆菌增强子基因degQ,最终构建了双功能枯草杆菌诱导型高效表达分泌载体pSBPTQ。将VasostatinⅠ基因作为靶基因检测sacBp.s.、α-amyT和degQ在pSBPTQ进行外源基因表达时的功能,结果表明,在蔗糖诱导下,sacB启动子有效启动了Vasostatin I基因的表达和分泌,α-amy T提高了VasostatinⅠ基因的转录效率,而degQ明显增强了VasostatinⅠ基因的表达水平。VasostatinⅠ基因在蔗糖诱导下成功表达并分泌到枯草杆菌细胞外,蛋白质分泌效率达到90%左右。质粒稳定性试验结果表明,经过40个世代之后,质粒pSBPTQ在枯草杆菌DB1342中仍旧保持在83%以上。     

A sucrose-inducible promoter system for the intra- and extracellular protein production in Bacillus megaterium

A sucrose-inducible promoter system (P(sacB)) from Bacillus megaterium was identified using a secretome approach. It was successfully employed for the extracellular production of the homologous levansucrase SacB (4252.4 U l(-1)) and the heterologous green fluorescent protein GFP (7.9 mg g(CDW)(-1)). Mutational analysis of B. megaterium P(sacB) allowed the identification of important promoter elements. The sucrose-inducible promoter provides a useful alternative to the established xylose-inducible promoter system (P(xylA)) for recombinant gene expression in B. megaterium.     

青霉素酶基因在枯草芽孢杆菌中的高效表达

以获得大量胞外青霉素酶为目的,将青霉素酶基因克隆至表达载体pWB980中,并转化到双蛋白酶缺陷的Bacillus subtilis DB104。重组菌在LB培养基中培养24小时后, SDS-PAGE分析发现目的蛋白分子量为28kDa,酶活力为339U/mL;通过筛选7种不同的发酵培养基发现4#培养基更利于青霉素酶的表达,最大酶活力为1580U/mL,较优化前提高了3.66倍,并对该重组菌进行了7L罐放大实验,结果显示在培养24小时产酶达到高峰,酶活力为1255.8 U/mL。     

β-半乳糖苷酶在枯草芽孢杆菌中的分泌表达

为检测本课题组构建的枯草芽孢杆菌分泌表达载体pGPST中启动子和信号肽的活性,将β-半乳糖苷酶基因插入表达载体的多克隆位点,构建含有β-半乳糖苷酶基因的重组质粒pGPST-lacZ,重组质粒转化枯草芽孢杆菌,分别测定液体培养基中上清液和菌体沉淀中β-半乳糖苷酶的活性。培养上清液中的酶活在22h达到峰值,约为26mU/mL,之后开始下降;菌体沉淀中的酶活在14h最高,达6mU/mL,而阴性对照pGPST没有检测到酶活性。结果表明分泌型表达载体中的启动子和信号肽具有较好的活性,能实现异源基因在枯草芽孢杆菌中的分泌表达。本试验为该表达载体的进一步研究和应用提供重要的数据资料,也为外源基因在枯草芽孢杆菌中的表达提供参考资料。该载体将在研究外源基因在枯草芽孢杆菌中表达发挥重要作用。     

Isolation and characterization of levansucrase-encoding gene from Bacillus amyloliquefaciens

The gene encoding levansucrase (LVS) from Bacillus amyloliquefaciens (sacB[BamP]) was isolated, sequenced and expressed in Bacillus subtilis. Analysis of the nucleotide sequence of sacB[BamP] reveals extensive homology with that of the B. subtilis LVS-encoding gene in the promoter and coding region. The sacB[BamP] gene cloned in a multicopy plasmid is induced by sucrose in B. subtilis.     

Expression, purification, and characterization of a thermophilic neutral protease from Bacillus stearothermophilus in Bacillus subtilis

The gene coding for a thermophilic neutral protease from Bacillus stearothermophilus was expressed in Bacillus subtilis DB104, under the control of the sacB gene promoter. This was followed by either the native signal peptide sequence of this protease or the signal peptide sequence of the sacB gene. The protease was purified 3.8-fold, with a specific activity of 16530 U mg-1. As analyzed by SDS-PAGE, the molecular mass of the expressed protease was about 35 kDa, and the optimal temperature and pH of the protease were 65℃ and 7.5, respectively. Moreover, it still had about 80% activity after 1 h reaction at 65℃.     

Nucleotide sequence of the gene for an alkaline endoglucanase from an alkalophilic Bacillus and its expression in Escherichia coli and Bacillus subtilis.

The gene for an alkaline endoglucanase from the alkalophilic Bacillus sp. KSM-64 was cloned into the HindIII site of pBR322 and expressed in Escherichia coli HB101. The nucleotide sequence of a 4.1-kb region of the HindIII insert had two open reading frames, ORF-1 and ORF-2. The protein deduced from ORF-1 was composed of 244 amino acids with an M(r) of 27,865. Subcloning analysis proved that the alkaline endoglucanase was encoded by ORF-2 (822 amino acids with an M(r) of 91,040). Upstream from ORF-2, there were three consensus like sequences of the sigma A-type promoter of Bacillus subtilis, a putative Shine-Dalgarno sequence (AGGAGGT), and a catabolite repression operator-like sequence (TGTAAGCGGTTAACC). The HindIII insert was subcloned into a shuttle vector, pHY300PLK, and the encoded alkaline endoglucanase gene was highly expressed both in E. coli and B. subtilis. One of the three promoter-like sequences in ORF-2 could be suitable for high levels of enzyme expression in both host organisms.     

The DNA sequence of the gene for the secreted Bacillus subtilis enzyme levansucrase and its genetic control sites

We present the sequence of a 2 kb fragment of the Bacillus subtilis Marburg genome containing sacB, the structural gene of levansucrase, a secreted enzyme inducible by sucrose. The peptide sequence deduced for the secreted enzyme is very similar to that directly determined by Delfour (1981) for levansucrase of the non-Marburg strain BS5. The peptide sequence is preceded by a 29 amino acid signal peptide. Codon usage in sacB is rather different from that in the sequenced genes of other secreted enzymes in B. subtilis, especially alpha-amylase. Genetic evidence has shown that the sacB promotor is rather far from the beginning of sacB (200 bp or more). The 200 bp region preceding sacB shows some of the features of an attenuator. A preliminary discussion of the putative workings and roles of this attenuator-like structure is proposed. sacRc mutations, which allow constitutive expression of levansucrase, have been located within the 450 bp upstream of sacB. It is shown that sacRc and sacR+ alleles control in cis the expression of the adjacent sacB gene.     

地衣芽孢杆菌高温α-淀粉酶异源表达研究

目的：以地衣芽孢杆菌高温α-淀粉酶基因（amyL）为报告基因,构建含不同启动子的枯草杆菌表达载体,转化枯草杆菌,并对重组菌的酶活进行分析,比较不同启动子对amyL基因在枯草杆菌中表达的影响。方法：以高温α-淀粉酶高产菌株B.licheniformis0204染色体DNA为模板,PCR扩增得到amyL并分别与PQ启动子和P43启动子进行连接构建表达载体pUB-PQ-amyL和pUB-P43-amyL,化学法转化枯草杆菌1A717,筛选得到重组转化子后对重组菌的表达产物进行SDS-PAGE和酶活检测。结果：重组菌摇瓶发酵105h后测定高温α-淀粉酶酶活,B.subtilis1A717（pUB-PQ-amyL）的最高酶活为280.1U/mL,B.subtilis1A717（pUB-P43-amyL）的最高酶活为190.5U/mL。结论：PQ启动子调控的高温α-淀粉酶最高表达水平是P43启动子调控的最高表达水平的1.47倍,说明PQ启动子能使amyL基因在枯草杆菌中更高效地表达。     

5'-noncoding region sacR is the target of all identified regulation affecting the levansucrase gene in Bacillus subtilis.

The regulation of the levansucrase gene sacB was studied in Bacillus subtilis strains. Fusions were constructed in which genes of cytoplasmic proteins such as lacZ were placed immediately downstream from sacR, the regulatory region located upstream from sacB. These fusions were introduced in mutants affected in sacB regulation. In all cases the marker gene was affected in the same way as sacB by the genetic context. This result is of particular interest for the sacU pleiotropic mutations, which affect sacB expression and other cellular functions such as the synthesis of several exocellular enzymes. We also showed that strains harboring sacU+ or sacU-hyperproducing alleles contained different amounts of sacB mRNA, which was proportional to their levansucrase secretion. We concluded that the sacU gene does not affect sacB expression at the level of secretion but acts on a target within sacR. We discuss the possibility that sacU acts on a part of sacR, a homologous copy of which was found upstream from the gene of another sacU-dependent secreted enzyme of B. subtilis, beta-glucanase.     

重组青霉素G酰化酶在枯草芽孢杆菌中的表达条件优化

 为获得巨大芽孢杆菌青霉素 G酰化酶 (PGA)的高产菌株和条件 ,构建了分泌表达 PGA的基因工程枯草杆菌菌株 ,对表达条件进行了优化 .以 LB作为初始培养基 ,考察了温度、苯乙酸、装液量、碳源对于工程菌 PGA产量的影响 .实验发现重组细胞产酶不再需要变温和苯乙酸诱导 .充足的通气量和适当浓度的淀粉可使细胞密度及 PGA表达量大为提高 .表达条件优化后 ,菌体 A60 0由 3提高到 2 0 ,PGA的表达量由 3～ 6U/ml提高到 35～ 40 U/ml,为目前生产用巨大芽孢杆菌表达量的 6倍 .     

内切葡聚糖酶基因在巨大芽孢杆菌中的表达及其酶学性质研究

通过PCR方法将已克隆的内切葡聚糖酶基因(GenBank No. DQ782954)信号肽编码序列去除, 然后与表达载体pHIS1525连接后转化大肠杆菌DH5a, 筛选出阳性转化子DH5 a -pHIS1525-G7并提取质粒进一步转化巨大芽孢杆菌WH320原生质体, 获得基因工程菌WH320-pHIS1525-G7。刚果红染色和SDS-PAGE分析表明该基因在巨大芽孢杆菌中得到了有效表达。基因工程菌经优化培养后, 胞外上清液中的酶活力可达889 U, 是出发菌株(即枯草芽孢杆菌C-36)的11.22倍。酶学性质研究表明: 该酶的最适反应温度与pH值分别为65℃与pH 6.0, 在pH 4.5~10.0范围内50℃保温30 min可保持在最高酶活的80%以上。     

Expression of the Bacillus pumilus chloramphenicol acetyltransferase gene in Bacillus subtilis, achieved by the P-R-promotor of phage lambda

The possibility of expression of the Bacillus pumilus chloramphenicol acetyltransferase gene (cat) in Bacillus subtilis from the pR promoter of phage lambda has been investigated in this work. For this purpose, the plasmid pPL703 carrying the B. pumilus DNA segment with the cat gene lacking promoter has been combined with the plasmid pBM21 containing the pR promoter. The recombinant plasmid pEL1 is capable of providing the 60 mkg/ml chloramphenicol resistance in Bac. subtilis cells.     

Expression of the Bacillus subtilis sacB gene leads to sucrose sensitivity in the gram-positive bacterium Corynebacterium glutamicum but not in Streptomyces lividans.

The expression of the structural gene (sacB) encoding Bacillus subtilis levansucrase in two gram-positive soil bacteria, Corynebacterium glutamicum ATCC 13032 and Streptomyces lividans 1326, was investigated. sacB expression in the presence of sucrose is lethal to C. glutamicum but not to S. lividans. While S. lividans secretes levansucrase into the medium, we could show that the enzyme is retained by C. glutamicum cells. Our results imply that the sacB gene can be used as a positive selection system in coryneform bacteria.     

Expression and purification of extracellular penicillin G acylase in Bacillus subtilis

Penicillin G acylase (PGA) is one of the most important enzymes for the production of semisynthetic beta-lactam antibiotics and their key intermediates. To enhance its expression, the PGA gene from Bacillus megaterium was amplified by PCR and subcloned into an expression vector under the control of the P43 promoter. The resulting construct was transferred into Bacillus subtilis WB600 and the transformant producing the most PGA was selected and designated SIBAS205. In contrast to the parent cells, which have to be induced by phenylacetic acid and cultured at 28 and 25 degrees C successively to produce PGA, the recombinant cells needed neither induction nor thermoregulation during fermentation at 37 degrees C. PGA was secreted and reached an expression level of 40 U/mL under optimized conditions. The enzyme was separated by centrifugation and purified by Al(2)O(3) adsorption and phenyl-Sepharose CL-4B hydrophobic chromatography with a yield of 85%. The purified enzyme had a specific activity of 45 U/mg protein.