8 research outputs found
Production, purification and characterization of celullase-free xylanase from Aspergillus terreus UL 4209
Aspergillus terreus, UL 4209 strain, isolated from the soil in South Africa was used to produce an extracellular cellulase-free xylanase in shake flask cultures containing oat spelt and/or birchwoodxylans. Maximum xylanase activity (35 U/ml) was observed after 96 h at 35ÂșC and pH 6 in 1% oat spelt xylan. The xylanase was purified to homogeneity by gel filtration on Sephacryl S-200. This enzyme wasfound to be a single subunit protein of 22 kDa showing optimal activity at 35ÂșC and pH 6. The enzyme retained 95% activity at 35 - 40ÂșC after 4 h incubation at pH 6 and at 50ÂșC the half-life was 5.8 h. Theapparent Km and Vmax values were 3.57 mg/ml and 55.5 mol/min per mg protein, respectively. MALDITOF and LC mass spectroscopy gave 8 peptide ions whose sequence alignments showed that thexylanase produced by this strain has homology with those of other Aspergillus strains such as A. terreus and A. versicolor. These observations showed that our strain produced a low molecular weight,acidophilic, and thermostable xylanase that may be considered for processes operated at moderate temperatures and pH such as preparation of baked cereal food, clarification of fruit juices andsaccharification of agro-residues
Optimization of decolorization of palm oil mill effluent (POME) by growing cultures of aspergillus fumigatus using response surface methodology
The conventional treatment process of palm oil mill effluent (POME) produces a highly colored effluent. Colored compounds in POME cause reduction in photosynthetic activities, produce carcinogenic by-products in drinking water, chelate with metal ions, and are toxic to aquatic biota. Thus, failure of conventional treatment methods to decolorize POME has become an important problem to be addressed as color has emerged as a critical water quality parameter for many countries such as Malaysia. Aspergillus fumigatus isolated from POME sludge was successfully grown in POME supplemented with glucose. Statistical optimization studies were conducted to evaluate the effects of the types and concentrations of carbon and nitrogen sources, pH, temperature, and size of the inoculum. Characterization of the fungus was performed using scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and Brunauer, Emmet, and Teller surface area analysis. Optimum conditions using response surface methods at pH 5.7, 35 A degrees C, and 0.57 % w/v glucose with 2.5 % v/v inoculum size resulted in a successful removal of 71 % of the color (initial ADMI of 3,260); chemical oxygen demand, 71 %; ammoniacal nitrogen, 35 %; total polyphenolic compounds, 50 %; and lignin, 54 % after 5 days of treatment. The decolorization process was contributed mainly by biosorption involving pseudo-first-order kinetics. FTIR analysis revealed that the presence of hydroxyl, C-H alkane, amide carbonyl, nitro, and amine groups could combine intensively with the colored compounds in POME. This is the first reported work on the application of A. fumigatus for the decolorization of POME. The present investigation suggested that growing cultures of A. fumigatus has potential applications for the decolorization of POME through the biosorption and biodegradation processes
Purification and Characterization of a Low Molecular Weight Endo-xylanase from Mushroom Termitomyces clypeatus
A low molecular weight endo-xylanase (EC 3.2.1.8) was purified from an edible
mushroom Termitomyces clypeatus grown in submerged medium with oat spelt xylan.
Xylanase was purified to apparent homogeneity by ammonium sulfate fractionation and gel
filtration chromatography. Its molecular weight was determined by gel filtration chromatography
and sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be 12 kDa. The
enzyme was found to be most active at 50°C and pH 5.0, being most stable at pH 6.5. The Km
for oat spelt xylan was determined to be 10.4 mg/ml. The specificities of the enzyme was
observed to be highly specific towards oat spelt xylan and was inhibited by mercuric chloride
(HgCl2), N-bromosuccinimide, and trans-1,2-diaminocyclohexane-NâČ,NâČ,NâČ,NâČ-tetraacetic acid
strongly. The inhibitory action of N-bromosuccinimide on enzyme confirmed the presence of
one tryptophan residue in its substrate-binding site. Amino acid analysis for xylanase showed
the presence of high amount of hydrophobic serine, glycine, threonine, and alanine residues.
The N-terminal sequencing study for the previously purified and characterized 56 kDa
xylanolytic amyloglucosidase reveal the presence of 33.30% identity with glucoamylase chain
A from Aspergillus awamori. The N-terminal sequence analysis of the present 12 kDa enzyme
showed highest similarity (72.22% identity) towards xylanase from Neurospora crassa