High-level expression of an endoxylanase gene from Bacillus sp. in Bacillus subtilis DB104 for the production of xylobiose from xylan

Optimal Production of β-Galactosidase from Lactobacillus fermentum for the Synthesis of Prebiotic Galactooligosaccharides (Gos)

The enzyme β-galactosidase (β-gal) has extensively used for improvement of lactose intolerance condition. Present study, was designed to assess the potential of β-gal enzyme produced by Lactobacillus fermentum, a kefir isolate, as a biocatalyst for the manufacture of prebiotic galactooligosaccharides (GOS) from lactose. The efficiency of L. fermentum to produce β-gal of 4,254 u/ml was determined by permeabilizing the cells with solvents such as sodium dodecyl sulfate (SDS) and chloroform. Different parameters contributing β-gal production including reaction time, temperature, pH, carbohydrates, and substrate concentration on L. fermentum were studied and optimum β-gal activity was found to be 6,232.13 u/ml. It was observed that different experimental parameters for pH (7.0), temperature (35°C), and carbohydrates (galactose) were statistically significant (p<0.05). L. fermentum was found to produce GOS by transgalactosylation catalysed by β-gal during lactose hydrolysis which yielded di, tri, and tetra oligosaccharides, confirmed by TLC and HPLC. The culture showed β-gal activity, suggesting biotechnological applications and a promising organism for industrial β-gal production.

Multiple integration of the gene ganA into the Bacillus subtilis chromosome for enhanced β-galactosidase production using the CRISPR/Cas9 system

The ganA gene from Bacillus subtilis encoding a β-galactosidase for degradation of the galactomannan was integrated in different loci of the B. subtilis chromosome employing the CRISPR/Cas9 system. Hereby a total of five copies of ganA cassettes in which the ganA gene was fused with the glucitol-promoter were inserted in the recipient chromosome wherein hypothetical, sporulation and protease genes were deleted. The strain with five copies of ganA expression cassette showed a β-galactosidase activity similar to the one with the same gene on a pUB110 derived multi-copy plasmid and under the same regulatory control of the glucitol promoter and GutR activator. The production of β-galactosidase in the strain with the multi-copy plasmid decreased rapidly when growth was performed under induced conditions and without antibiotic selection. In contrast, the strain with the five copies of ganA in the chromosome produced β-galactosidase for at least 40 generations. This demonstrates that the CRISPR/Cas9 system is a valuable and easy tool for constructing stable producer strains. The bigger efforts that are needed for the multiple target gene integration into the chromosome compared to cloning in expression vectors were justified by the higher stability of the target genes and the lack of antibiotic resistance genes.

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.

Recombinant Xylanase from Bacillus tequilensis BT21: Biochemical Characterisation and Its Application in the Production of Xylobiose from Agricultural Residues

Bacterial strain Bacillus tequilensis BT21 isolated from marine sediments was found to produce extracellular xylanase. The xynBT21 gene encoding xylanase enzyme was cloned and expressed in Escherichia coli. The gene encoded a protein consisting of 213 amino acid residues with calculated molecular mass of 23.3 kDa. Purified recombinant xylanase had optimum activity at 60 °C and pH=6. The enzyme was highly stable in alkaline pH, at pH=7 it remained 100% active for 24 h, while its activity increased at pH=8 and 9 during incubation. B. tequilensis BT21 xylanase had alkaline pI of 9.4 and belongs to glycosyl hydrolase family 11. The mode of action of XynBT21 on beechwood xylan and xylooligosaccharides was studied. It hydrolysed xylooligosaccharides and beechwood xylan yielding mainly xylobiose (X₂) with a small amount of xylose (X₁), indicating that XynBT21 was probably an endo-acting xylanase. Enzymatic hydrolysis using wheat bran as a substrate revealed that xylanase reported here has the potential to produce xylobiose from wheat bran. Xylooligosaccharides, especially xylobiose, have strong bifidogenic properties and are increasingly used as a prebiotic. This is the first report that describes this novel xylanase enzyme from marine B. tequilensis BT21 used for the release of xylobiose from wheat bran.

Extracellular targeting of an active endoxylanase by a TolB negative mutant of Gluconobacter oxydans

Gluconobacter (G.) oxydans strains have great industrial potential due to their ability to incompletely oxidize a wide range of carbohydrates. But there is one major limitation preventing their full production potential. Hydrolysis of polysaccharides is not possible because extracellular hydrolases are not encoded in the genome of Gluconobacter species. Therefore, as a first step for the generation of exoenzyme producing G. oxydans, a leaky outer membrane mutant was created by deleting the TolB encoding gene gox1687. As a second step the xynA gene encoding an endo-1,4-β-xylanase from Bacillus subtilis was expressed in G. oxydans ΔtolB. More than 70 % of the total XynA activity (0.91 mmol h−1 l culture−1) was detected in the culture supernatant of the TolB mutant and only 10 % of endoxylanase activity was observed in the supernatant of G. oxydans xynA. These results showed that a G. oxydans strain with an increased substrate spectrum that is able to use the renewable polysaccharide xylan as a substrate to produce the prebiotic compounds xylobiose and xylooligosaccharides was generated. This is the first report about the combination of the process of incomplete oxidation with the degradation of renewable organic materials from plants for the production of value-added products.

Surface display of recombinant proteins on Escherichia coli by BclA exosporium of Bacillus anthracis

Background

The anchoring motif is one of the most important aspects of cell surface display as well as efficient and stable display of target proteins. Thus, there is currently a need for the identification and isolation of novel anchoring motifs.

Results

A system for the display of recombinant proteins on the surface of Escherichia coli was developed using the Bacillus anthracis exosporal protein (BclA) as a new anchoring motif. For the surface display of recombinant proteins, the BAN display platform was constructed in which a target protein is linked to the C-terminus of N-terminal domain (21 amino acids) of BclA. The potential application of BAN platform for cell surface display was demonstrated with two model proteins of different size, the Bacillus sp. endoxylanase (XynA) and monooxygenase (P450 BM3m2). Through experimental analysis including outer membrane fractionation, confocal microscopy and activity assay, it was clearly confirmed that both model proteins were successfully displayed with high activities on the E. coli cell surface.

Conclusions

These results of this study suggest that the strategy employing the B. anthracis BclA as an anchoring motif is suitable for the display of heterologous proteins on the surface of E. coli and consequently for various biocatalytic applications as well as protein engineering.

Novel xylanase from a holstein cattle rumen metagenomic library and its application in xylooligosaccharide and ferulic Acid production from wheat straw

A novel gene fragment containing a xylanase was identified from a Holstein cattle rumen metagenomic library. The novel xylanase (Xyln-SH1) belonged to the glycoside hydrolase family 10 (GH10) and exhibited a maximum of 44% identity to the glycoside hydrolase from Clostridium thermocellum ATCC 27405. Xyln-SH1 was heterologously expressed, purified, and characterized. A high level of activity was obtained under the optimum conditions of pH 6.5 and 40 °C. A substrate utilization study indicated that Xyln-SH1 was cellulase-free and strictly specific to xylan from softwood. The synergistic effects of Xyln-SH1 and feruloyl esterase (FAE-SH1) were observed for the release of xylooligosaccharides (XOS) and ferulic acid (FA) from wheat straw. In addition, a high dose of Xyln-SH1 alone was observed to improve the release of FA from wheat straw. These features suggest that this enzyme has substantial potential to improve biomass degradation and industrial applications.

In vitro fermentation of prebiotics by Lactobacillus plantarum CFR 2194: selectivity, viability and effect of metabolites on β-glucuronidase activity

Prebiotic Fructooligosaccharides (FOS) escape metabolism in upper GI tract undergo microbial metabolism in colon and thereby influence the nature, type and number of intestinal microbiota to improve host's health. The present study focuses on the ability of Lactobacillus plantarum CFR 2194 to utilize FOS as a selective carbon and energy source. The effect of fermentative metabolites of L. plantarum on the β-glucuronidase was also investigated. A total of 16 strains of lactobacilli were assessed for their ability to ferment oligosaccharides. L. plantarum CFR 2194, an isolate from kanjika was found to utilize FOS effectively. Lactic acid was the main metabolic end product, followed by acetic acid, butyric acid, formic acid and ethanol. The inhibitory effects of these metabolites have been confirmed through the reduction of β-glucuronidase activity. L. plantarum when co-cultured with β-glucuronidase producing E. coli, in a basal media containing FOS as an energy source, could inhibit the growth of the pathogen during the course of fermentation. The results showed that L. plantarum CFR 2194 has the ability to utilize the prebiotic FOS as a selective carbon and energy source. The organism could inhibit the growth of the pathogen which produces β-glucuronidase and lowered its activity by the metabolites of FOS which indicates the probable use of L. plantarum through dietary intervention in combating colon carcinogenesis.

Beneficial effect of xylo-oligosaccharides and fructo-oligosaccharides in streptozotocin-induced diabetic rats

The beneficial influences of xylo-oligosaccharides (XOS) obtained from alkali-pretreated corncob and fructo-oligosaccharides (FOS) obtained from cane sugar were evaluated in experimental diabetes. These oligosaccharides were supplemented at 10 % (w/w) in the basal diet of streptozotocin-induced diabetic Wistar rats, while the control rats were fed with a basal diet for a period of 6 weeks. Both the oligosaccharides exerted favourable influences in diabetic rats by significantly improving body weight and reducing hyperglycaemia and cholesterol. The characteristic diabetic complications such as severe glucosuria, proteinuria and advanced glycation end products in renal tissue, diabetic nephropathy, and blood creatinine and urea concentrations were notably reduced. Besides, these oligosaccharide supplementations significantly increased the activity of antioxidant enzymes – catalase and glutathione reductase – in the blood of diabetic rats. Supplementation of XOS and FOS resulted in a significant increase in the bifidobacteria and lactobacilli population in the caecum. The present study indicates that XOS and FOS have an ameliorating influence on metabolic abnormalities associated with diabetes, besides conferring an optimal milieu of lactobacilli and bifidobacteria, thus suggesting their potential health benefit in diabetics.

Rheofermentometer fermentation and breadmaking characteristics of dough containing xylo-oligosaccharide hydrolyzate from wheat bran

The sugar composition of a xylo-oligosaccharide enzymolysis solution (XES) hydrolyzed from wheat bran and bread containing XES were studied. The effects of the XES on fermentation properties of dough and on bread crumb and crust color characteristics are reported. The composition of sugars was determined by high performance liquid chromatography (HPLC), and the fermentation properties of dough and bread color were determined by Rheofermentometer F3 and Chroma Meter CR-400, respectively. xylo-Oligosaccharides (XOS) (51.3%) and xylose (39.2%) were the major sugars in the XES. XOS remained in the XES-containing bread after breadmaking processes (xylotriose, xylotetraose, and xylopentaose, 21.1%), with xylopentaose accounting for 14.4%. Maximum dough height (Hm) was significantly increased by XES, while the maximum gaseous release height (Hm') was not affected. XES increased the brownness index of the crumb and crust of bread when compared to the that of control bread. Consumer acceptability scores of control and XES containing breads were similar.

Functional characterisation of a recombinant xylanase fromPichia pastorisand effect of the enzyme on nutrient digestibility in weaned pigs

Thexyn2gene of a filamentous mesophilic fungus,Trichoderma reesei, coding xylanase 2 (Xyn2) was previously expressed inPichia pastoris. In the present study, the recombinant Xyn2 was prepared from a 15 litre fermenter, and subsequently characterised. It has been confirmed to have a molecular mass of 21 kDa, an optimal pH of 6·0 and an optimal temperature of 60°C. When tested using oat-spelt xylan, it showed aKmand catalytic rate constant (kcat) of 1·1 mg/ml and 512·4/s, respectively. Analysis of the products from oat-spelt xylan degradation confirmed that the enzyme was an endoxylanase with xylotriose and xylobiose as the main degradation products. The unprocessed Xyn2 was supplemented to a xylan-containing diet to determine its influences on performance and nutrient digestibilities by weaned pigs. Results showed that the average body-weight gain increased 16·9 % when piglets received Xyn2 at a concentration of 500 U/kg diet. There also was a positive (0·05 < P < 0·10) effect on the digestibility values of crude protein, ash, Ca and acid-detergent fibre with Xyn2 supplementation. The potential benefits of Xyn2 in the nutrition of weaned pigs should make it an alternative applicant for industrial xylanase production.

Value addition to corncob: production and characterization of xylooligosaccharides from alkali pretreated lignin-saccharide complex using Aspergillus oryzae MTCC 5154

Comparison of various pretreatments such as mild alkali/acid treatments and pressure cooking of corncob to expose its lignin-saccharide complex has been carried out to enhance enzymatic hydrolysis of xylan to xylooligosaccharides (XOS). Scanning electron micrographs of lignin-saccharide complex of native and pretreated corncob powder showed that the complex was greatly altered during alkali pretreatment. Hydrolysis of alkali pretreated corncob powder using a commercial endoxylanase produced 81+/-1.5% of XOS in the hydrolyzate equivalent to 5.8+/-0.14 mg ml(-1) of XOS. Reaction parameters for the production of XOS from corncob using endoxylanase from Aspergillus oryzae MTCC 5154 were optimized and an XOS yield of 10.2+/-0.14 mg ml(-1) corresponding to 81+/-3.9% with 73.5% xylobiose was obtained. HPLC/RID and ESI/MS analysis of XOS mixture and purified fractions showed that XOS was a mixture of neutral oligosaccharides of DP, 2-7.

Cloning, expression, and characterization of a new Streptomyces sp. S27 xylanase for which xylobiose is the main hydrolysis product

A xylanase gene, xynBS27, was cloned from Streptomyces sp. S27 and consisted of 693 bp encoding a 230-residue protein, including a putative 41-residue signal peptide. Belonging to the glycoside hydrolase family 11, XynBS27 exhibits the maximum identity (75.9%) to the xylanase from Streptomyces sp. zxy19. Recombinant XynBS27 was overexpressed in Pichia pastoris, and the xylanase activity was 7624.0 U/ml after high-cell-density fermentation in 3.7-L fermenter. The purified recombinant XynBS27 had a high specific activity of 3272.0 U/mg. The optimum temperature and pH for XynBS27 activity was 65 degrees C and pH 6.5, respectively. XynBS27 showed good pH stability and retained more than 80% of the maximum activity after incubation in buffers with pH ranging between 4.0 and 12.0 at 37 degrees C for 1 h. The main hydrolysis product of xylan by XynBS27 was xylobiose (>75%), which was good for human health derived from its ability to modulate the intestinal function. The attractive biochemical characteristics of XynBS27 suggest that it may be a good candidate in a variety of industrial applications.

Corncob-induced endo-1,4-beta-d-xylanase of Aspergillus oryzae MTCC 5154: production and characterization of xylobiose from glucuronoxylan

Eight different fungi were cultivated in a peptone-yeast extract medium containing 1% oat spelt xylan (OSX) to evaluate endo-1,4-beta-xylanase secretion for xylooligosaccharide (XOS) production. Aspergillus oryzae MTCC 5154, Aspergillus flavus , Aspergillus niger , and Aspergillus ochraceus showed significant titers of endoxylanases, which were further used for the production of XOS from birch wood xylan (BWX). A. oryzae produced 89.5 +/- 1.13% XOS in the hydrolysate at 24 h of reaction. The effect of OSX, BWX, and raw corncob on the induction of endoxylanase in A. oryzae was studied, and the xylanase activity was maximum at 96 h of cultivation in 3% corncob containing medium. XOS produced at 36 h of reaction was 5.87 +/- 0.53 mg/mL (12 +/- 2% xylose, 48 +/- 2.43% xylobiose, and 40 +/- 3.6% higher oligomers) from 1% BWX . HPLC/refractive index detection and ESI/MS analysis of fractions obtained by GPC corresponded to neutral and 4- O-methyl-alpha- d-glucuronic acid substituted acidic oligosaccharides. The major fraction, beta- d-xylopyranosyl-(1-->4)- d-xylanopyranose was characterized using (13)C NMR.

Production of xylobiose from the autohydrolysis explosion liquor of corncob using Thermotoga maritima xylanase B (XynB) immobilized on nickel-chelated Eupergit C

In this study, a thermostable recombinant xylanase B (XynB) from Thermotoga maritima MSB8 was immobilized on nickel-chelated Eupergit C 250L. This immobilized XynB was then used to hydrolyze the autohydrolysis explosion liquor of corncob (AELC) in a packed-bed enzyme reactor for continuous production of xylooligosaccharides, especially xylobiose. When tested in batch hydrolysis of AELC, the immobilized XynB still retained its relative activity of 92.5% after 10 cycles of hydrolysis at 90 degrees C. The immobilized XynB retained 83.6% of its initial hydrolysis activity even after 168 h of hydrolysis reaction at 90 degrees C and demonstrated a half-life time of 577.6 h (24 days) for continuous hydrolysis. HPLC showed that xylobiose (49.8%) and xylose (22.6%) were the main hydrolysis products yielded during continuous hydrolysis. Xylobiose was adsorbed on an activated charcoal column and eluted with a linear gradient of 15% (v/v) ethanol to yield xylobiose with 84.7% of recovery. Also, the purity of xylobiose was up to 97.2% as determined by HPLC. Therefore, the immobilized XynB was suitable for the efficient production of xylobiose from AELC. This is the first report on the immobilization of xylanase for xylobiose production.

Production of xylooligosaccharides from xylans by extracellular xylanases from Thermobifida fusca

Xylooligosaccharides are produced for use as a valuable food sweetener or additive. They have many beneficial biomedical and health effects. In this study, a process for producing xylooligosaccharides from lignocellulolytic agricultural waste was developed. Bagasse, corncob, wheat bran, and peanut shell were used as carbon sources for production of xylanolytic enzymes from Thermobifida fusca NTU22. When using bagasse as the carbon source, the xylanolytic enzymes that simultaneously accumulated in the broth in a 500 mL Hinton flask after 72 h of cultivation at 50 degrees C were measured as xylanase (14.0 U/mL), beta-xylosidase (74.1 mU/mL), and acetyl esterase (29.1 mU/mL). The optimum pH and temperature for xylanases were 6.0-8.0 and 70 degrees C, respectively. Six proteins with xylanase activity were identified by zymogram analysis of isoelectric focusing gel. This was followed by heat treatment at 70 degrees C for 30 min that eliminated 90% of the beta-xylosidase activity. The xylanase and acetyl esterase activities were still 100%. Two percent of xylan extracted from the bagasse was then hydrolyzed by heat-treated crude xylanase preparation at 60 degrees C, pH 7.0, for 10 h. The xylooligosaccharides that accumulated in the broth were about 23.7%. After the purification process by activated charcoal chromatography, the purity of xylooligosaccharides was 71.4%.

Codon optimizedThermobifida fusca hydrolase secreted byBacillus megaterium

Production and secretion of a 28,172 Da hydrolase from Thermobifida fusca (TFH) in Bacillus megaterium MS941 and WH323 was investigated in shake flask and pH controlled bioreactors. Successful production of heterologous TFH was achieved by adapting the original tfh gene to the optimal codon usage of B. megaterium. A codon adaption index close to one was reached. The codon optimized tfh was cloned into an open reading frame with DNA sequence for the N-terminal signal peptide of B. megaterium lipase A and a C-terminal His(6)-tag, all under the control of a xylose inducible promoter. Successful TFH production and secretion were observed using batch reactor cultivations with complex medium. Expression of the tfh gene from the P(xylA) promoter and secretion of produced TFH were compared in detail to batch reactor cultivations with semi-defined growth medium. For the first time, significant TFH secretion was achieved using a semi-defined medium in glucose limited fed batch cultivations yielding 10-fold higher cell densities compared to LB medium cultivation. Comparable volumetric TFH activities were obtained for both cultivation strategies. Surprisingly, measured specific TFH activities exhibited drastic discrepancies between preparations from LB and semi-defined medium grown B. megaterium. TFH recovery by Ni-chelate affinity chromatography resulted in higher purification factors when LB medium was used. These results indicated that secreted TFH is favorably produced by batch cultures of B. megaterium WH323 in LB medium.

Development of a biofilm production-deficient Escherichia coli strain as a host for biotechnological applications

Bacteria form biofilms by adhering to biotic or abiotic surfaces. This phenomenon causes several problems, including a reduction in the transport of mass and heat, an increase in resistance to antibiotics, and a shortening of the lifetimes of modules in bioindustrial fermentors. To overcome these difficulties, we created a biofilm production-deficient Escherichia coli strain, BD123, by deleting genes involved in curli biosynthesis and assembly, Delta(csgG-csgC); colanic acid biosynthesis and assembly, Delta(wcaL-wza); and type I pilus biosynthesis, Delta(fimB-fimH). E. coli BD123 remained mostly in the form of planktonic cells under the conditions tested and became more sensitive to the antibiotics streptomycin and rifampin than the wild-type E. coli MG1655: the growth of BD123 was inhibited by one-fourth of the concentrations needed to inhibit MG1655. In addition, the transformation efficiency of BD123 was about 20 times higher than that of MG1655, and the production and secretion of recombinant proteins were approximately 16% and approximately 25% greater, respectively, with BD123 than with MG1655. These results indicate that the newly created biofilm production-deficient strain of E. coli displays several key properties that substantially enhance its utility in the biotechnology arena.

Developments in the use of Bacillus species for industrial production

Bacillus species continue to be dominant bacterial workhorses in microbial fermentations. Bacillus subtilis (natto) is the key microbial participant in the ongoing production of the soya-based traditional natto fermentation, and some Bacillus species are on the Food and Drug Administration's GRAS (generally regarded as safe) list. The capacity of selected Bacillus strains to produce and secrete large quantities (20-25 g/L) of extracellular enzymes has placed them among the most important industrial enzyme producers. The ability of different species to ferment in the acid, neutral, and alkaline pH ranges, combined with the presence of thermophiles in the genus, has lead to the development of a variety of new commercial enzyme products with the desired temperature, pH activity, and stability properties to address a variety of specific applications. Classical mutation and (or) selection techniques, together with advanced cloning and protein engineering strategies, have been exploited to develop these products. Efforts to produce and secrete high yields of foreign recombinant proteins in Bacillus hosts initially appeared to be hampered by the degradation of the products by the host proteases. Recent studies have revealed that the slow folding of heterologous proteins at the membrane-cell wall interface of Gram-positive bacteria renders them vulnerable to attack by wall-associated proteases. In addition, the presence of thiol-disulphide oxidoreductases in B. subtilis may be beneficial in the secretion of disulphide-bond-containing proteins. Such developments from our understanding of the complex protein translocation machinery of Gram-positive bacteria should allow the resolution of current secretion challenges and make Bacillus species preeminent hosts for heterologous protein production. Bacillus strains have also been developed and engineered as industrial producers of nucleotides, the vitamin riboflavin, the flavor agent ribose, and the supplement poly-gamma-glutamic acid. With the recent characterization of the genome of B. subtilis 168 and of some related strains, Bacillus species are poised to become the preferred hosts for the production of many new and improved products as we move through the genomic and proteomic era.

Expression of Bacillus circulans Teri-42 xylanase gene in Bacillus subtilis

The xylanase gene of Bacillus circulans Teri-42 was cloned in both B. subtilis and Escherichia coli. The enzyme activity was almost 87% higher in B. subtilis (pBA7) than in E. coli (pAQ4). No cellulase activity was detected in the clones, B. subtilis (pBA7) and E. coli (pAQ4). Approximately 1120 U (80%) of the xylanase was secreted extracellularly by the clone B. subtilis (pBA7) as compared to 79 U (88%) excreted in E. coli (pAQ4). In B. subtilis (pBA7) the optimal xylanase activity was at pH 7.0 and 50 degrees C, which was the same as that of the parent B. circulans Teri-42. The recombinant xylanase in B. subtilis was more stable at higher temperatures than the parent B. circulans Teri-42. Purification of xylanase from the clone B. subtilis (pBA7) showed a 71 kDa polypeptide similar to that observed in B. circulans Teri-42.