<p>Burkholderia cepacia (Bcc) BiogenCC E76 isolate is an endophytic bacterium producing cell wall degrading enzyme, glucanase, and antagonistic to fungal pathogens, such as Magnaporte grisea and Colletotrichum gloeosporioides. The<br />glucanase is able to lyse fungal cell walls composed of glucan causing disintegrity of mycelia and fungi fail to infect plants. The purpose of this study was to clone, express, and characterize 48 kDa subunit of β-1,3-glucanase from Bcc isolate BiogenCC E76 using the Escherichia coli expression system. The 1,300 bp of the β-1,3-glucanase gene was constructed using the pET-32b<br />vector in BamHI-HindIII restriction sites to generate the pET-Glu plasmid. The gene was fused with nucleotides sequence encoding Trx-tag, His-tag, and S-tag producing 65 kDa of recombinant β-1,3-glucanase. Gene expression in the construct was controlled by the T7 promoter and Trx-tag start codon through IPTG induction. The recombinant β-1,3-glucanase was then purified and its activities were tested at different pH and temperature conditions. Results showed that E. coli carrying pET-Glu overexpressed a 65 kDa protein in induced culture as a soluble protein that was expressed in periplasm. Purification result of the crude extract of the recombinant protein obtained 27% pure enzymes with a specific activity of 1,207.976 U/mg and purity level of 3.9 fold. This recombinant glucanase demonstrated optimal activity at 40°C and pH 5–7. A deeper study is needed to understand the role of 48 kDa subunit of β-1,3-glucanase has in antagonistic mechanism of Bcc against pathogenic fungi.</p>

The increasing of rice plant production has to deal with some constraints caused by pathogen infection such as by bacteria, viruses or fungi. Endophytic bacteria have antagonistic capacity against fungi and was used to prevent the invasion of the pathogen. Burkholderia cepacia is one of the endophytic bacteria carrying genes expressed in defense system against fungi by producing glucanase enzyme. The aim of this research was to clone a gene encoding β-1,4-glucanase from B. cepacia into the expression system in Escherichia coli. The clone of glucanase gene was isolated by PCR technique using DNA fragment of B. cepacia from rice plants. The Glu 1320 primer pairs were designed based on the glucanase gene nucleotide sequence on online database, with the length of the amplicon DNA of 1300 bp. Results from BlastN and BlastX analysis showed that the DNA fragment which was cloned into pGEM-T Easy vector had similarity with Endo-1,4-D-glucanase gene of Burkholderia mallei and Burkholderia pseudomallei. The identity of the cloned DNA fragment was 99% and E-value 0.0. Proteomic analysis of the amino acid sequence was done using Server Expasy Proteomic and the total of amino acid was 451 with, molecular weight of 48.363 kDa and isoelectric point (pI) of 5.87. The signal peptide had cleavage sites on position 23 and 24 in amino acid AAAAE. Recombinant protein clone was obtained from Protein Data Bank (PDB) database with the code of 4q2b.2.A. The protein consist of 349 residu which formed the secondary structure like of 7 betahairpin pairs, 20 turn, 3 helix-3/10, and 17 alpha-helix.