Screening, purification and characterization of cellulase from cellulase producing bacteria in molasses.

OBJECTIVES: This study was conducted to isolate, screening and purification of cellulase from bacteria present in sugar industry waste (molasses) and characterization by morphological and biochemical analysis. RESULTS: Based on experiments, three bacterial strains produced clear transparent zone into carboxymethyl cellulose (CMC) agar plate were identified as cellulase producing bacteria. Different culture parameters such as pH, temperature, incubation period, substrate concentration and carbon sources were optimized for enzyme production. According to the morphological and biochemical tests, the isolated strains were identified as Paenibacillus sp., Bacillus sp. and Aeromonas sp. The first strain Paenibacillus sp. showed high potentiality for maximum cellulase production (0.9 µmol ml-1 min-1) at pH 7.0 after 24 h of incubation at 40 °C in a medium containing 1.0% CMC. Then Paenibacillus sp. was selected for enzyme purification by ammonium sulfate precipitation, DEAE-cellulose and CM-cellulose column chromatography, respectively. In last step of purification, specific activity, recovery and purification fold were 2655 U/mg, 35.7% and 9.7, respectively. The molecular weight of the purified cellulase was found to be 67 kDa by SDS-PAGE, had an optimal pH and temperature at 7.0 and 40 °C. According to substrate specificity, the purified cellulase had high specificity on CMC substrate which indicated it to be an endo-ß-1,4-glucanase.

Cloning, expression, and cell surface localization of Paenibacillus sp. strain W-61 xylanase 5, a multidomain xylanase.

We have shown that a xylan-degrading bacterium, W-61, excretes multiple xylanases, including xylanase 5 with a molecular mass of 140 kDa. Here, we emend the previously used classification of the bacterium (i.e., Aeromonas caviae W-61) to Paenibacillus sp. strain W-61 on the basis of the nucleotide sequence of the 16S rRNA gene, and we clone and express the xyn5 gene encoding xylanase 5 (Xyn5) in Escherichia coli and study the subcellular localization of Xyn5. xyn5 encodes 1,326 amino acid residues, including a 27-amino-acid signal sequence. Sequence analysis indicated that Xyn5 comprises two family 22 carbohydrate-binding modules (CBM), a family 10 catalytic domain of glycosyl hydrolases, a family 9 CBM, a domain similar to the lysine-rich region of Clostridium thermocellum SdbA, and three S-layer-homologous (SLH) domains. Recombinant Xyn5 bound to a crystalline cellulose, Avicel PH-101, while an N-terminal 90-kDa fragment of Xyn5, which lacks the C-terminal half of the family 9 CBM, did not bind to Avicel PH-101. Xyn5 was cell bound, and the cell-bound protein was digested by exogenous trypsin to produce immunoreactive and xylanolytic fragments with molecular masses of 80 and 60 kDa. Xyn5 was exclusively distributed in the cell envelope fraction consisting of a peptidoglycan-containing layer and an associated S layer. Thus, Paenibacillus sp. strain W-61 Xyn5 is a cell surface-anchored modular xylanase possessing a functional cellulose-binding module and SLH domains. Possible cooperative action of multiple xylanases produced by strain W-61 is discussed on the basis of the modular structure of Xyn5.

Purification, characterization and amplification of a 1.8 kbp fragment of xylanase 5 from Aeromonas caviae W-61.

Aeromonas caviae W-61 produces multiple extracellular xylanases, the xylanases 1, 2, 3, 4, and 5. In this study, we purified and characterized the xylanase 5 of A. caviae W-61, and amplified a part of xylanase 5 gene (xyn5). The purified xylanase 5 was found to be a single polypeptide with molecular mass of 140 kDa. It was an endo-beta-1,4-xylanase showing optimum temperature 40 degrees C and optimum pH 6.0. Xylobiose, xylotriose, xylotetrose, xylopentose, xylohexose and a small amount of xylose were detected as the hydrolysis products. The N-terminal amino acid sequence and several internal amino acid sequences of xylanases 5 were determined. From the sequence, a 1.8 kbp fragment was amplified by PCR using forward and reverse primers. DNA sequencing confirmed the presence of nucleotide sequences corresponding to the N-terminal amino acid sequence and the internal amino acid sequences of xylanase 5.