A xylanase DNA sequence with a total length of 642 bp was previously isolated from a xylanolytic Klebsiellapneumoniae. Xylanase gene primers were designed with the addition of BamH1 and EcoR1 restriction enzymesites in order get a full xylanase gene that is in-frame with pSTAG expression vector. The isolated xylanasegene was amplified using the designed primers through PCR, then cloned and expressed in E. coli BL21 (DE3).In-silico characterization showed that the recombinant xylanase has a molecular weight of 23.9 kDa and a pI of9.32. The signal peptide cleavage site for the recombinant xylanase was predicted to be between residues 61and 62. The activity of the crude recombinant xylanase was 2.015 U/mL, which was higher than the crudenative xylanase activity, with maximum at 0.642 U/mL. Staining of the birchwood xylan agar plate with Congored showed a clearing zone around E. coli BL21 (DE3) colonies with recombinant pSTAG plasmid evenwithout being induced with IPTG. This implied leaky expression of the E. coli BL21 (DE3) secretion system,which recognized the signal sequence of the recombinant xylanase, and proceeded to cleave and secreted outthe mature protein into the culture medium. MALDI-TOF analysis of a 20 kDa protein present in the culturemedium confirmed that the recombinant xylanase had been secreted into the culture medium.
Aims: Phytophthora capsici and Fusarium solani are common fungal pathogens causing severe diseases that lead to economic loss in pepper industry, especially in Sarawak. In response to the infections, chemical approach is more common; nevertheless, biological control is more favorable to control fungal pathogens. Biological control approach greatly reduces the problems associated with chemical applications and it restores balance of the natural environment. Here we present the ongoing work to study the action of antagonistic bacteria, Bacillus sp. and Pseudomonas sp., that produce volatile and non-volatile antifungal compounds against P. capsici and F. solani on pepper plants. Methodology and results: A total of seven bacterial candidates were isolated from different locations and tested for their antagonistic properties against P. capsici and F. solani in a dual culture assay and extracellular metabolite test. Extracellular hydrolytic enzymes production was also monitored and followed by genotypic indentification. Preliminary antagonism tests indicated that bacterial isolate Pep3 and Pep4 inhibit up to 50% of the growth of P. capsici and F. solani as compared to the control. Subsequent investigation on extracellular hydrolytic enzyme production revealed that both bacterial isolates are capable of secreting hydrolytic enzymes. Microscopic and genotypic analyses identified the bacterial isolates Pep3 as Bacillus amyloliquefaciens (KJ461444) and Pep4 as Pseudomonas pachastrellae (KM460937). Conclusion, significance and impact of study: B. Amyloliquefaciens (KJ461444) and P. pachastrellae (KM460937) inhibited the growth of P. capsici and F. solani thus reflecting the potential of the produced metabolites to be purified and used in combating plant pathogenic fungi.
The chemistry of aspirin and chalcone derivatives has been extensively studied and developed as one of thepharmaceutically important molecules. In this study, new aspirin-chalcone derivatives have been successfullysynthesized and characterized via FTIR, 1H and 13C NMR spectroscopy. The antibacterial activities ofsynthesized compounds were investigated towards Escherichia coli ATCC 8739 via turbidimetric kineticmethod. The newly synthesized aspirin-chalcone derivatives, however showed poor antibacterial activityagainst E. coli ATCC 8739 at the concentration of 50, 80 and 100 ppm. The effect of the molecular structureof the synthesized compounds on the antibacterial activity is discussed.
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