Molecular cloning of a Bacillus subtilis xylanase gene in Escherichia coli

In silico studies on bacterial xylanase enzyme: Structural and functional insight

Xylans are the second most abundant form of hemicelluloses and are the second most abundant polysaccharide in nature after cellulose. To degrade xylan, microbes produce mainly xylanase enzyme. Wide range of microorganisms like fungi, bacteria, yeast, marine algae etc. are capable of producing xylanase. Main source of xylanase is fungi but industrial production of bacterial xylanase is low cost, easy downstream process and high production rate. To understand primary, secondary and tertiary structure of xylanase, in silico composition of amino acids, basic physiological characteristics; viz., pI, molecular weight, instability index, GRAVY, molar extinction coefficient, secondary structure, presence of functional domain and motifs, phylogenetic tree, salt bridge compositions are determined. In silico study of xylanase focused on 36 different bacterial sources are performed by retrieving FASTA and PDB sequences using RCSB PDB. FASTA and PDB files are proceed further in ExPASy-ProtParam, RAMPAGE, QMEAN, MEME, PSIPRED, InterProScan, MOTIF scan, ERRAT, Peptide cutter, ESBRI and MEGA 7. The instability index range (16.90-38.78) clearly indicates that the protein is highly stable. α-helix mean value (27.11%) infers the protein is dominated by α-helix region. The aliphatic index (39.80-90.68) gives information that the protein is highly thermostable, prevalence by alanine amino acid in aliphatic side chain. No transmembrane domain was found in the protein which confirms the enzyme is extracellular in nature. Ancestor chart analysis confirmed that it is a part of carbohydrate metabolic process and more specifically a member of glycoside hydrolase super family.

A computational method for prediction of xylanase enzymes activity in strains of Bacillus subtilis based on pseudo amino acid composition features

Xylanases are hydrolytic enzymes which based on physicochemical properties, structure, mode of action and substrate specificities are classified into various glycoside hydrolase (GH) families. The purpose of this study is to show that the activity of the members of the xylanase family in the specified pH and temperature conditions can be computationally predicted. The proposed computational regression model was trained and tested with the Pseudo Amino Acid Composition (PseAAC) features extracted solely from the amino acid sequences of enzymes. The xylanases with experimentally determined activities were used as the training dataset to adjust the model parameters. To develop the model, 41 strains of Bacillus subtilis isolated from field soil were screened. From them, 28 strains with the highest halo diameter were selected for further studies. The performance of the model for prediction of xylanase activity was evaluated in three different temperature and pH conditions using stratified cross-validation and jackknife methods. The trained model can be used for determining the activity of newly found xylanases in the specified condition. Such computational models help to scale down the experimental costs and save time by identifying enzymes with appropriate activity for scientific and industrial usage. Our methodology for activity prediction of xylanase enzymes can be potentially applied to the members of the other enzyme families. The availability of sufficient experimental data in specified pH and temperature conditions is a prerequisite for training the learning model and to achieve high accuracy.

Cloning and heterologous expression of cellulose free thermostable xylanase from Bacillus brevis

Xylanase gene isolated from Bacillus brevis was expressed in E. coli BL21. Sequencing of the gene (Gen Bank accession number: HQ179986) showed that it belongs to family 11 xylanases. The recombinant xylanase was predominantly secreted to culture medium and showed mesophilic nature (optimum activity at 55°C and pH 7.0). The cell free culture medium exhibited 30 IU/ml xylanse activity. The enzyme did not show any cellulose activity and was active under wide range of temperature (40°C to 80°C) and pH (4 to 9). The enzyme showed considerable thermo stability and regained over 90% of activity, when returned to 55°C after boiling for 5 min. These physiochemical properties of B. brevis xylanse show high potential of its applications in paper and pulp industry.

Characterization of a new Providencia sp. strain X1 producing multiple xylanases on wheat bran

Providencia sp. strain X1 showing the highest xylanase activity among six bacterial isolates was isolated from saw-dust decomposing site. Strain X1 produced cellulase-free extracellular xylanase, which was higher in wheat bran medium than in xylan medium, when cultivated at pH 8.0 and 35°C. Zymogram analysis of crude preparation of enzymes obtained while growing on wheat bran and birchwood xylan revealed the presence of seven and two distinct xylanases with estimated molecular weight of 33; 35; 40; 48; 60; 75; and 95 kDa and 33 and 44 kDa, respectively. The crude xylanases were produced on wheat bran medium and showed optimum activity at pH 9.0 and 60°C. The thermotolerance studies showed activity retention of 100% and 85% at 40°C and 60°C after 30 min preincubation at pH 9.0. It was tolerant to lignin, ferulic acid, syringic acid, and guaiacol and retained 90% activity after ethanol treatment. The enzyme preparation was also tolerant to methanol and acetone and showed good activity retention in the presence of metal ions such as Fe²⁺, Mg²⁺, Zn²⁺, and Ca²⁺. The crude enzyme preparation was classified as endoxylanase based on the product pattern of xylan hydrolysis. Pretreatment of kraft pulp with crude xylanases for 3 h at 60°C led to a decrease in kappa number by 28.5%. The properties of present xylanases make them potentially useful for industrial applications.

A rapid and simple method for preparing an insoluble substrate for screening of microbial xylanase

Several types of enzymes, including cellulases and xylanases, are required to degrade hemicelluloses and cellulose, which are major components of lignocellulosic biomass. Such degradative processes can be used to produce various useful industrial biomaterials. Screening methods for detecting polysaccharide-degrading microorganisms include the use of dye-labeled substrates in growth medium and culture plate staining techniques. However, the preparation of screening plates, which typically involves chemical cross-linking to synthesize a dye-labeled substrate, is a complicated and time-consuming process. Moreover, such commercial substrates are very expensive, costing tenfold more than the natural xylan. Staining methods are also problematic because they may damage relevant microorganisms and are associated with contamination of colonies of desirable organisms with adjacent unwanted bacteria. In the present study, we describe a sonication method for the simple and rapid preparation of an insoluble substrate that can be used to screen for xylanase-expressing bacteria in microbial populations. Using this new method, we have successfully isolated a novel xylanase gene from a xylolytic microorganism termed Xyl02-KBRB and Xyl14-KBRB in the bovine rumen.

Recombinant expression and characterization of XynD from Bacillus subtilis subsp. subtilis ATCC 6051: a GH 43 arabinoxylan arabinofuranohydrolase

The complete genome sequence of Bacillus subtilis reveals that sequences encoding several hemicellulases are co-localised with a gene (xynD) encoding a putative family 43 glycoside hydrolase that has not yet been characterised. In this work, xynD has been isolated from genomic DNA of B. subtilis subsp. subtilis ATCC 6051 and cloned for cytoplasmatic expression in Escherichia coli. Recombinant XynD (rXynD) was purified using ion-exchange chromatography and gel permeation chromatography. The enzyme had a molecular mass of approximately 52 kDa, a pI above 9.0 and releases alpha-L-arabinose from arabinoxylo-oligosaccharides as well as arabinoxylan polymers with varying degree of substitution. Using para-nitrophenyl-alpha-L-arabinofuranoside as substrate, maximum activity was observed at pH 5.6 and 45 degrees C. The enzyme retained its activity over a large pH range, while activity was lost after pre-incubation above 50 degrees C. Gas-liquid chromatography and proton nuclear magnetic resonance spectrometry analysis indicated that rXynD specifically releases arabinofuranosyl groups from mono-substituted C-(O)-2 and C-(O)-3 xylopyranosyl residues on the xylan backbone. As rXynD did not display endoxylanase, xylosidase or arabinanase activity and was inactive on arabinan, we conclude that this enzyme is best described as an arabinoxylan arabinofuranohydrolase.

A dual protein expression system in Bacillus subtilis

We have developed a dual expression system for the simultaneous overexpression of two proteins in Bacillus subtilis. Two candidate genes, xylanase (xynA) and glucanase (bglS) from B. subtilis strain 168, which were engineered with independent Shine-Dalgarno (SD) sequences, were cloned in tandem into a transfer vector, which was then transformed into B. subtilis strain 1A304 (phi105MU331). The genes were under the transcriptional control of a strong promoter of a bacteriophage, phi105, where transcription was initiated upon thermal induction. Six constructs were made to compare the factors that affected the yields of the gene products. The expression level of each candidate gene was found to correspond to its position relative to the phage promoter, irrespective of the identity of the insert. The lower expression level of the second insert might have been due to limited resources for protein synthesis, a short half-life of the mRNA, or an early termination of the RNA polymerase. Curiously, gene duplications in tandem did not lead to further increase in production.

Molecular and biotechnological aspects of xylanases

Hemicellulolytic microorganisms play a significant role in nature by recycling hemicellulose, one of the main components of plant polysaccharides. Xylanases (EC 3.2.1.8) catalyze the hydrolysis of xylan, the major constituent of hemicellulose. The use of these enzymes could greatly improve the overall economics of processing lignocellulosic materials for the generation of liquid fuels and chemicals. Recently cellulase-free xylanases have received great attention in the development of environmentally friendly technologies in the paper and pulp industry. In microorganisms that produce xylanases low molecular mass fragments of xylan and their positional isomers play a key role in regulating its biosynthesis. Xylanase and cellulase production appear to be regulated separately, although the pleiotropy of mutations, which causes the elimination of both genes, suggests some linkage in the synthesis of the two enzymes. Xylanases are found in a cornucopia of organisms and the genes encoding them have been cloned in homologous and heterologous hosts with the objectives of overproducing the enzyme and altering its properties to suit commercial applications. Sequence analyses of xylanases have revealed distinct catalytic and cellulose binding domains, with a separate non-catalytic domain that has been reported to confer enhanced thermostability in some xylanases. Analyses of three-dimensional structures and the properties of mutants have revealed the involvement of specific tyrosine and tryptophan residues in the substrate binding site and of glutamate and aspartate residues in the catalytic mechanism. Many lines of evidence suggest that xylanases operate via a double displacement mechanism in which the anomeric configuration is retained, although some of the enzymes catalyze single displacement reactions with inversion of configuration. Based on a dendrogram obtained from amino acid sequence similarities the evolutionary relationship between xylanases is assessed. In addition the properties of xylanases from extremophilic organisms have been evaluated in terms of biotechnological applications.

Identification of glu-277 as the catalytic nucleophile of Thermoanaerobacterium saccharolyticum beta-xylosidase using electrospray MS

Thermoanaerobacterium saccharolyticum beta-xylosidase is a member of family 39 of the glycosyl hydrolases. This grouping comprises both retaining beta-d-xylosidases and alpha-l-iduronidases. T. saccharolyticum beta-xylosidase catalyses the hydrolysis of short xylo-oligosaccharides into free xylose via a covalent xylosyl-enzyme intermediate. Incubation of T. saccharolyticum beta-xylosidase with 2,4-dinitrophenyl 2-deoxy-2-fluoro-beta-d-xyloside resulted in time-dependent inactivation of the enzyme (inactivation rate constant ki=0.089 min-1, dissociation constant for the inactivator Ki=65 microM) through the accumulation of a covalent 2-deoxy-2-fluoro-alpha-d-xylosyl-enzyme, as observed by electrospray MS. Removal of excess inactivator and regeneration of the free enzyme through transglycosylation with either xylobiose or thiobenzyl xyloside demonstrated that the covalent intermediate was kinetically competent. Peptic digestion of the 2-deoxy-2-fluoro-alpha-d-xylosyl-enzyme intermediate and subsequent analysis by electrospray ionization triple-quadrupole MS in the neutral-loss mode indicated the presence of a 2-deoxy-2-fluoro-alpha-d-xylosyl peptide. Sequence determination of the labelled peptide by tandem MS in the daughter-ion scan mode permitted the identification of Glu-277 (bold and underlined) as the catalytic nucleophile within the sequence IILNSHFPNLPFHITEY.

Effect of the replication mode of a plasmid on the stability of multimeric endoxylanase genes in Bacillus subtilis

Effect of the replication mode of a plasmid on the stability of tandemly multimerized endoxylanase genes and a gene dose-dependent expression of the endoxylanase were studied in Bacillus subtilis. The structural genes encoding an endoxylanase, carrying its original promoter and ribosomal binding sequence, were tandemly multimerized and cloned into the Escherichia coli-B. subtilis shuttle plasmid, pJH27 delta 88 or pMTL500e, which has a rolling circle-replicon or a theta (theta)-replicon in B. subtilis, respectively. The cloned dimers in pJH27 delta 88, which has a rolling circle-replicon, spontaneously rearranged to monomers in B. subtilis DB104, whereas those in pMTL500e, having a theta (theta)-replicon, were stably maintained. Expression level of the endoxylanase was proportional to the gene dosage in multimers. The endoxylanase activity in the supernatant increased from 80 U ml-1 with pMTL-1x containing a monomer of the gene to 165 U ml-1 with pMTL-4x containing a tetramer. These results indicate that high level expression of the endoxylanase gene can be obtained by tandemly multimerizing the genes in a plasmid with a theta (theta)-replicon.

Molecular cloning and characterization of an endoxylanase gene of Bacillus sp. in Escherichia coli

A gene encoding an endoxylanase of Bacillus sp. was cloned and expressed in Escherichia coli. The entire nucleotide sequence of a 1,620 bp SmaI fragment containing the endoxylanase gene was determined. The endoxylanase gene was 639 bp long and encoded 213 amino acids which showed up to 96% amino acid homology with other endoxylanases. The endoxylanase produced by E. coli harboring pKJX4 was purified by ion-exchange chromatography (DE-52 and CM-52) and its N-terminal sequence was determined to be Ala-Gly-Thr-Asp-Tyr-Trp-Gln-Asn-Trp-Thr-Asp-Gly-Gly-Gly-Thr. The endoxylanase expressed in E. coli was identical to that of the original Bacillus sp. whose molecular weight was approximately 20,400. Most of the produced endoxylanase was localized in the periplasmic space of E. coli. When the endoxylanase was reacted with 2% oat spelts xylan (w/v) at 40 degrees C for 10 h, the major product was xylobiose which is known to be a selective growth stimulant to one of the healthy intestinal microflora, Bifidobacteria.

Construction of a recombinant cellulolytic Escherichia coli

A 1.2-kb DNA fragment from Bacillus subtilis CD4 encoding endo-beta-1,4-glucanase and cellobiase activities was cloned and expressed in Escherichia coli. Carboxymethylcellulase (CMCase) and cellobiase activities were detected in a cell-free lysate of recombinant (re-) E. coli (Ec). The re-enzymes were functional in Ec, as it utilized carboxymethylcellulose, soluble cellulose and cellobiose as sole carbon sources for growth.

Cloning and extracellular expression in Escherichia coli of xylanases from an alkaliphilic thermophilic Bacillus sp. NCIM 59

A genomic DNA library of an alkaliphilic thermophilic Bacillus was constructed in Escherichia coli with pUC 8 vector and was screened using a Congo red xylan plate clearance assay. Six xylanase positive transformants having identical inserts showed immunological reactivity towards polyclonal antibodies raised against purified xylanase (M(r) 15,800) from the Bacillus. A 4.5-kb HindIII-EcoRI subfragment was found to code for two xylanases of M(r) 14,500 and 35,000. Equivalent amounts of xylanase activity were detected from IPTG induced and noninduced recombinants irrespective of the orientation of the 4.5-kb insert with respect to the lac promoter, indicating that xylanase gene expression was under the control of its own promoter. 95% of the xylanase activity (2 U/ml) was found in the extracellular culture filtrate. The hydrolysis of xylan by the recombinant xylanases yielded mainly xylobiose.

Two beta-glycanase genes are clustered in Bacillus polymyxa: molecular cloning, expression, and sequence analysis of genes encoding a xylanase and an endo-beta-(1,3)-(1,4)-glucanase

Two genes, xynD and gluB, encoding a xylanase and an endo-beta-(1,3)-(1,4)-glucanase (lichenase) from Bacillus polymyxa have been cloned and expressed in Escherichia coli and Bacillus subtilis. A sequenced DNA fragment of 4,466 bp contains both genes, which are separated by 155 bp. The xynD and gluB genes encode proteins of 67.8 kDa (XYND) and 27 kDa (GLUB). Two peptides with molecular masses of 62 and 53 kDa appear in cell extracts of E. coli and culture supernatants of B. subtilis clones containing the xynD gene. Both peptides show xylanase activity in zymogram analysis. The XYND enzyme also shows alpha-L-arabinofuranosidase activity. The XYND peptide and the xylanase XYNZ from Clostridium thermocellum (O. Grépinet, M. C. Chebrou, and P. Béguin, J. Bacteriol. 170:4582-4588, 1988) show 64% homology in a stretch of about 280 amino acids.

Low-molecular-weight xylanase from Trichoderma viride

An endo-1,4-beta-xylanase (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) has been isolated from a commercial preparation of Trichoderma viride. The molecular weight was 22,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the pI value was 9.3. The xylanase was a true xylanase without cellulase activity. When the N-terminal amino acid sequence of the first 50 residues was compared with that of a xylanase from Schizophyllum commune, strong evidence for homology was found, with more than 50% amino acid identity. T. viride xylanase also possessed extensive identity with a proposed amino-terminal consensus sequence of xylanases from bacteria.

Cloning, sequencing, and expression of a xylanase gene from the anaerobic ruminal bacterium Butyrivibrio fibrisolvens

A gene coding for xylanase activity, xynA, from the anaerobic ruminal bacterium Butyrivibrio fibrisolvens 49 was cloned into Escherichia coli JM83 by using plasmid pUC19. The gene was located on a 2.3-kilobase (kb) DNA insert composed of two adjacent EcoRI fragments of 1.65 and 0.65 kb. Expression of xylanase activity required parts of both EcoRI segments. In E. coli, the cloned xylanase enzyme was not secreted and remained cell associated. The enzyme exhibited no arabinosidase, cellulase, alpha-glucosidase, or xylosidase activity. The isoelectric point of the cloned protein was approximately 9.8, and optimal xylanase activity was obtained at pH 5.4. The nucleotide sequence of the 1,535-base-pair EcoRV-EcoRI segment from the B. fibrisolvens chromosome that included the xynA gene was determined. An open reading frame was found that encoded a 411-amino-acid-residue polypeptide of 46,664 daltons. A putative ribosome-binding site, promoter, and leader sequence were identified. Comparison of the XynA protein sequence with that of the XynA protein from alkalophilic Bacillus sp. strain C-125 revealed considerable homology, with 37% identical residues or conservative changes. The presence of the cloned xylanase gene in other strains of Butyrivibrio was examined by Southern hybridization. The cloned xylanase gene hybridized strongly to chromosomal sequences in only two of five closely related strains.

Cloning of a Thermomonospora fusca xylanase gene and its expression in Escherichia coli and Streptomyces lividans

Thermomonospora fusca chromosomal DNA was partially digested with EcoRI to obtain 4- to 14-kilobase fragments, which were used to construct a library of recombinant phage by ligation with EcoRI arms of lambda gtWES. lambda B. A recombinant phage coding for xylanase activity which contained a 14-kilobase insert was identified. The xylanase gene was localized to a 2.1-kilobase SalI fragment of the EcoRI insert by subcloning onto pBR322 and derivatives of pBR322 that can also replicate in Streptomyces lividans. The xylanase activity produced by S. lividans transformants was 10- to 20-fold higher than that produced by Escherichia coli transformants but only one-fourth the level produced by induced T. fusca. A 30-kilodalton peptide with activity against both Remazol brilliant blue xylan and xylan was produced in S. lividans transformants that carried the 2.1-kilobase SalI fragment of T. fusca DNA and was not produced by control transformants. T. fusca cultures were found to contain a xylanase of a similar size that was induced by growth on xylan or Solka Floc. Antiserum directed against supernatant proteins isolated from a Solka Floc-grown T. fusca culture inhibited the xylanase activity of S. lividans transformants. The cloned T. fusca xylanase gene was expressed at about the same level in S. lividans grown in minimal medium containing either glucose, cellobiose, or xylan. The xylanase bound to and hydrolyzed insoluble xylan. The cloned xylanase appeared to be the same as the major protein in xylan-induced T. fusca culture supernatants, which also contained at least three additional minor proteins with xylanase activity and having apparent molecular masses of 43, 23, and 20 kilodaltons.

Cloning and expression in Escherichia coli of a xylanase gene from Bacteroides ruminicola 23

A gene coding for xylanase activity in the ruminal bacterial strain 23, the type strain of Bacteroides ruminicola, was cloned into Escherichia coli JM83 by using plasmid pUC18. AB. ruminicola 23 genomic library was prepared in E. coli by using BamHI-digested DNA, and transformants were screened for xylanase activity on the basis of clearing areas around colonies grown on Remazol brilliant blue R-xylan plates. Six clones were identified as being xylanase positive, and all six contained the same 5.7-kilobase genomic insert. The gene was reduced to a 2.7-kilobase DNA fragment. Xylanase activity produced by the E. coli clone was found to be greater than that produced by the original B. ruminicola strain. Southern hybridization analysis of genomic DNA from the related B. ruminicola strains, D31d and H15a, by using the strain 23 xylanase gene demonstrated one hybridizing band in each DNA.

Molecular cloning of an endoglucanase gene from an alkalophilic Bacillus sp. and its expression in Escherichia coli

One of the cellulase genes from alkalophilic Bacillus sp. strain N-4 was cloned in pBR322. A recombinant plasmid, pYBC107, expressing carboxymethyl cellulase (CMCase) was isolated, and the size of the cloned HindIII fragment was found to be 5.5 kilobases. The restriction map of pYBC107 showed a different pattern from those of pNKI and pNKII (N. Sashihara, T. Kudo, and K. Horikoshi, J. Bacteriol. 158:503-506, 1984). When the HindIII fragment from pYBC107 was subcloned into pYEJ001, there was a 3.8-fold increase in CMCase activity over that observed with pYBC107. Plasmid pYBC108 constructed by treatment of pYBC107 with HindIII and EcoRI expressed the CMCase activity, although to a limited extent. To verify the originality of cloned pYBC107 from Bacillus sp., we analyzed the restriction digest by Southern blotting.

Structure and expression of genes coding for xylan-degrading enzymes of Bacillus pumilus

The complete nucleotide sequence of the beta-xylosidase gene (xynB) of Bacillus pumilus IPO and its flanking regions was established. A 1617-bp open reading frame for beta-xylosidase, a homodimer enzyme, was observed. The amino acid sequence of the N-terminal region and the molecular mass 62607 Da) of the beta-xylosidase subunit, deduced from the DNA sequence, agreed with the result obtained with the purified enzyme. The Shine-Dalgarno sequence was found 8 bp upstream of the initiation codon, ATG. The xylanase gene (xynA) of the same strain was 4.6 kbp downstream of the 3' end of xynB, and its DNA sequence was reported in our previous paper [Fukusaki, E., Panbangred, W., Shinmyo, A. & Okada, H. (1984) FEBS Lett. 171, 197-201]. The results of the Northern hybridization suggested that the mRNA of xynA and xynB were produced separately. The 5' and 3' ends of the xynA and xynB gene were mapped with nuclease S1. The '-10' regions for promoter sequences of both genes were similar to the consensus sequence for B. subtilis RNA polymerases, the '-35' regions were different from all the known promoters for B. subtilis RNA polymerases.

Plasmid stability in immobilized and free recombinant Escherichia coli JM105(pKK223-200): importance of oxygen diffusion, growth rate, and plasmid copy number

Stability of the plasmid pKK223-200 in Escherichia coli JM105 was studied for both free and immobilized cells during continuous culture. The relationship between plasmid copy number, xylanase activity, which was coded for by the plasmid, and growth rate and culture conditions involved complex interactions which determined the plasmid stability. Generally, the plasmid stability was enhanced in cultured immobilized cells compared with free-cell cultures. This stability was associated with modified plasmid copy number, depending on the media used. Hypotheses are presented concerning the different plasmid instability kinetics observed in free-cell cultures which involve the antagonistic effects of plasmid copy number and plasmid presence on the plasmid-bearing/plasmid-free cell growth rate ratio. Both diffusional limitation in carrageenan gel beads, which is described in Theoretical Analysis of Immobilized-Cell Growth, and compartmentalized growth of immobilized cells are proposed to explain plasmid stability in immobilized cells.

Crystallization and preliminary X-ray studies of Bacillus pumilus IPO xylanase

The xylan-degrading enzyme xylanase, from Bacillus pumilus IPO, has been crystallized. The crystals are monoclinic, space group P21 with a = 40.8 A, b = 66.8 A, c = 34.7 A and beta = 103.0 degrees. The asymmetric unit contains one molecule of Mr 22,500. The crystals diffract to at least 2.5 A resolution, and they are suitable for X-ray crystal structure analysis at high resolution.

Cloning of the xylanase gene of Streptomyces lividans

The xylanase (xln) gene of Streptomyces lividans 1326 was cloned by functional complementation of the xylanase-negative and beta-1,4-glucan-glucanohydrolase-negative double mutant of S. lividans using the multicopy plasmid pIJ702. Three clones had a common 2-kb DNA fragment as determined by restriction mapping and Southern hybridization. These clones secreted a xylanase of Mr 43,000 which reacted with specific anti-xylanase antibodies and corresponded exactly to the enzyme previously isolated from the wild-type strain. The DNA fragment likely carried the full structural gene, the xln promoter and also the regulatory sequence, since the xylanase activity was inducible by xylan. Enzyme levels of up to 380 IU/ml of culture filtrate were obtained.

Isolation and the 5'-end nucleotide sequence of Bacillus licheniformis alpha-amylase gene

We have isolated and determined the 5'-end nucleotide sequence of the alpha-amylase gene from Bacillus licheniformis ATCC 14580. The alpha-amylase produced by this strain is thermostable and of liquefying type. The gene was originally cloned in a bacteriophage lambda 1059 vector. A subclone containing a 5.3 X 10(3)-base insert in pBR322 was further characterized. The nucleotide sequence coding for the 5' end of the structural gene together with the sequence coding for the upstream control regions was determined. The deduced N-terminal amino acid sequence was identical with the previously published amino acid sequence of B. licheniformis alpha-amylase. There was also very strong homology to the N-terminal sequence of Bacillus amyloliquefaciens alpha-amylase. The Mr of the thermostable alpha-amylase, as determined in vitro in a cell-free transcription/translation system of Escherichia coli, was about 55 000.