Abstract
The current study aimed to optimize the production of cellulase and chitinase enzymes by plant growth promoting rhizobacteria (PGPR). Bacteria were pre-isolated from soil and identified as; Pseudomonas fluorescens NBRC (KW1), Serratia liquefaciens ATCC 27592 (EW1), Bacillus subtilis SBMP4 (EF1) and Bacillus megaterium NBRC 15308 (TF2). The effect of different growth parameters including; pH, temperature, carbon and nitrogen sources, and incubation periods were optimized for production of cellulase and chitinase enzymes by the selected bacterial strains. Three strains mainly, B. subtilis SBMP4, S. liquefaciens ATCC 27592 and P. fluorescens NBRC) recorded positive results for cellulase production. B. subtilis SBMP4 (EF1) and S. liquefaciens ATCC 27592 (EW1) strains demonstrated significant ability to produce cellulase at 40°C, while P. fluorescens NBRC (KW1) strain showed the maximum enzyme production at 30°C. Carboxymethyl cellulose gave the highest cellulase production compared to the other carbon sources. Chitinase enzyme was optimally produced by B. subtilis SBMP4 and S. liquefaciens ATCC 27592 strains under primary screening. B. subtilis SBMP4 had the strongest ability to produce chitinase at 40oC, while S. liquefaciens ATCC 27592 at 30oC. The optimum pH observed was at pH 6.0 to get the maximum chitinase production by S. liquefaciens ATCC 27592. Potassium nitrate (KNO3) as an inorganic nitrogen source presented the highest chitinase production by B. subtilis SBMP4, whereas yeast extract demonstrated significant chitinase production by S. liquefaciens ATCC 27592.
Highlights
Enzyme technology is an interdisciplinary field, and enzymes are routinely used in many environmental-friendly industrial sectors
Evaluating the cellulase enzyme activity at different incubation temperatures revealed that B. subtilis SBMP4 (EF1) and S. liquefaciens ATCC 27592 (EW1) had the strongest ability to produce cellulase at 40°C (Fig.1)
Current results are closed those of Frandberg and Schnurer, (1994) who reported that the optimum temperature for the activity of chitinase produced by B. pabuli was at 40°C
Summary
Enzyme technology is an interdisciplinary field, and enzymes are routinely used in many environmental-friendly industrial sectors. Many microorganisms produce a wide variety of hydrolytic enzymes against different substrate, such as cellulose and chitin. Cellulose makes up the cell walls of most plants and it is the most abundant biological polymer on the earth. (1998) documented that cellulose is a strong fibrous crystalline polysaccharide that resists hydrolysis, and is water insoluble. According to Venkata et al, (2013); Vijayaraghavan et al, (2016), cellulose consist of thousands of D-glucose units that are linked together with β-1, 4-glycosidic linkage. It is generally degraded by Cellulase, which can hydrolyze the β 1,4 glycosidic linkage to release glucose (Perez et al, 2002; AbouTaleb et al, 2009 )
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