A highly cellulolytic actinomycete SR1 was locally isolated from rice straw and provisionally identified as Thermomonospora viridis. Optimum pH, temperature, carbon and nitrogen sources for its cellulase production were 6.5, 35°C, Carboxymethyl cellulase (CMC) and yeast extract, respectively whereas those of cellulase activity were 7.5, 40°C, CMC and peptone respectively. The effects of various metal ions and different reductant and inhibitors on its cellulase activity were investigated. Univalent Ag+ was found to decrease the enzyme activity whereas increased by bivalent Mg2+. Ethylene diamine tetraacetic acid (EDTA) caused remarkable decrease of cellulase activity but β-Mercaptoethanol stimulated its cellulase activity. Bangladesh J. Bot. 50(2): 395-404, 2021 (June)
It has been known that the synthesis of cellulolytic enzymes in microorganisms is regulated by induction and repression system 1 . Cellulase of most microbes is strongly induced by cellulose or the compounds related to its hydrolytic products 2 and repressed by readily metabolizable carbon sources such as glucose 3 . However, the exact role of a compound to act as an inducer or a repressor varies from organism to organism. Cellobiose is a strong inducer in Neurospora crassa 4 and Sporotrichum pulverulentum 1 but it is a relatively poor inducer in Trichoderma ressei 5 when compared with saphorose. In cellulose-producing microbes, cellulose is a common inducer of cellulase formation [6][7] . Since cellulose is insoluble and impermeable to organism's soluble oligosaccharides such as cellobiose, lactose or saphorose is considered to act as a direct inducer of cellulase [8][9][10][11] . Of these oligosaccharides, cellobiose is a common product formed from cellulose by exo-cellobiohydrolase and is considered to be a natural inducer 12 . Cellobiose octaacetate was found to be solubilized by acetyl esterase secreted into the culture broth 13 and the hydrolysate consisting of a series of acetylcellobioses including mono-, di-, tri-O-acetylcellobioses could stimulate cellulase induction 14 . In this study, cellulose production by an actinomycete isolate, Streptomyces albolongus A 5 , was investigated using cellobiose octaacetate (COA) as an inducer for cellulose biosynthesis.Streptomyces albolongus A 5 was isolated from saw dust on selective cellulolytic medium and identified using standard procedure 15 . Unless otherwise stated, cellulase production was carried out in shake-flask cultures in Winstead's medium with an initial pH 6.5 containing 1.2% carboxymethylcellulose (CMC) with or without supplementation of 0.6% cellobiose octaacetate (COA) at 35°C for 5 days. After incubation, the culture filtrates were centrifuged to remove cells and other solids and the clear culture supernatants were used for enzyme assay and other analyses. Reducing sugar in the culture filtrates and the enzyme assay mixtures was estimated by using Nelson's modification of Somogyi method 16 using glucose as standard. Soluble protein in culture filtrates was estimated following the method described by Lowry et al. 17 . The absorbance was read at 650 nm. Culture filtrates obtained by growing the organism on CMC medium was used for estimation of the degree of saccharification (%) using the following equation: Degree of saccharification (%) = Reducing sugar (mg/ ml) / Substrate concentration (mg/ml) x 100. Carbooxymethylcellulase (CMCase) activity was determined by mixing 2 ml of culture supernatant to 2 ml substrate (1%CMC in phosphate buffer, pH 6.5), 1 ml of phosphate buffer and incubating the reaction mixture at 35°C for 2 h. Filter paper cellulase (FPase) was measured by incubating 2 ml of culture supernatant in 1 ml of phosphate buffer (pH 6.5) containing 50 mg Whatman No. 1 filter paper strip (1 x 6 cm) in a test tube. The reaction mixture was...
Chili field antagonistic actinomycetes Streptomyces fulvoviridis was isolated and tested for optimum antimicrobial metabolite production. Maximum antimicrobial metabolite production was found at temperature 35 0 C and pH 8.0 and on 4 th day of incubation in shaking condition. The medium consisting of beef extract -0.75%, peptone -0.25%, NaCl -1.5%, KCl -1.0%, MgCl 2 -1.0%, FeSO 4 -1.0% was screened out as suitable medium for maximum antimicrobial production supplemented individually with four carbon sources of which sucrose was found as the best carbon source. The antimicrobial metabolite was found to be stable at pH and temperature up to 11.0 and 100ºC, respectively. The active agent was best extracted with chloroform. The antimicrobial spectrum of the metabolite was wide and shows activity against -Shigella dysenteriae (AE 14612), Shigella sonnei (CRL, ICDDR, B), Salmonella typhi (AE14296), Vibrio cholerae (AE14748), Pseudomonas aeruginosa (CRL, ICDDR, B), Bacillus cereus (BTCC19), Staphylococcus aureus (ATCC6538), Bacillus subtilis (BTTC17) and Bacillus megaterium (BTTC18).
In this study, 15 isolates of Pseudomonas aeruginosa were recovered in Cetrimide agar medium from aseptically collected swab samples. Antibiotic susceptibility test revealed highest resistance against Rifampicin (100%) followed by Penicillin (80%), Erythromycin (73.33%), Cephalosporin group (13.33-60%) and Aminoglycoside group (26.67%). The most effective group of antibiotic was Carbapenem with 6.67% resistance. Among 15 isolates, 3 were having highest Multiple Antibiotic Resistance (MAR) index were identified as Pseudomonas aeruginosa (P1, P2 and P3) by API®20NE microbial identification kit. Minimum inhibitory concentration (MIC) of the isolates P1, P2 and P3 was 3.05μg/mL, 0.76μg/mL and 3.05μg/mL for Meropenem whereas for Ceftriaxone it was 12.207μg/mL, 12.207μg/mL and 781.25μg/mL, respectively. Minimum bactericidal concentration (MBC) of Meropenem and Ceftriaxone was same for the isolates P1 and P2 i.e., 48.83μg/mL and 195.313μg/mL, respectively but in case of P3 it was 781.25μg/mL for both antibiotics. In case of 70% ethanol, the MIC and MBC was 1:4 dilutions (for isolate P3, MBC was 1:2 dilutions) whereas for Savlon®, MIC and MBC was 1% and 2% solution, respectively. All of the three isolates were biofilm former according to test tube assay and microtitre plate assay whereas modified congo red agar assay indicated only one isolate as biofilm former. The results suggest that post-operative wound infection may serve as a reservoir for multidrug resistant biofilm forming P. aeruginosa which may complicate the treatment regime unless proper treatment ensured based on antibiotic/antiseptic susceptibility test.Asian J. Med. Biol. Res. March 2018, 4(1): 105-116
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