PENGHASILAN DAN PENGGUNAAN ENZIM PENGURAI LIGNIN OLEH PHANEROCHAETE CHRYSOSPORIUM ME 446 SURDS

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Date
1997-04
Authors
IBRAHIM, DARAH
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Abstract
The optimization of some governing parameters in the enzyme production revealed that an increment of 50% was obtained using the medium composition containing 0.1 % (w/v) carbon source; 2.4 mM . ammonium dihydrogen phosphate and 0.4 mM veratryl alcohol. The cultivation was performed at 35 - 37°C, with an agitation speed of 150 rpm and inoculum size of 6 x 106 spores/ml. The production of lignin degrading enzymes by P. chrysosporium was found to be significant in the presence of complex polysaccharides such as barly straws and rice husks. The maximum lignin peroxidase activity after four days of cultivation was 82.0 mU/ml, while the activity of manganese.peroxidase was 58.0 - 63.0 mU/ml after seven days. The higher production of lignin peroxidase and manganese peroxidase by free cells of P. chrysosporium of about 520.0 mU/ml and 350.0 mU/ml, respectively, was obtained when cultivated in a tubular air-lift bioreactor, when compared to a looped air-lift bioreactor or a stirred tank bioreactor. The optimised production parameters used in the bioreactor were aeration rate of 1.0 wm, 1.0% (w/v) of glucose and the inoculum size of 8 x 106 spores/ml. The enzymes production was further improved by entrapping the P. chrysosporium cells in nylon sponge using the same medium composition. A maximum production of 950.0 mU/ml of lignin peroxidase and 620.0 mU/ml of manganese peroxidase was obtained. Solid state fennentation system (SSF) using rice husks as substrate was performed. Using the optimised fermentation system of 200g rice husks as substrate, water content of 0.4 ml/g substrate, 0.1 % (w/w) ammonium dihydrogen phosphate, 0.5% (w/w) yeast extract, 0.068 gIl veratryl alcohol, i'noculum size of 1.0 x 107 spores/ml and inCUbation at 30°C, a maximum production of about 165.0 U/g lignin peroxidase and 110.0 U/g manganese peroxidase were achieved after 10 days cultivation. The lignin peroxidase was purified by means of ammonium sulphate precipitation and an anion exchange chromatography, using a prepacked Mono Q column. The resolution from Mono Q column resulted in six different peaks with the total recovery of 51 %, of which 29% was peak 5 (P5)· Ps was purified about 23 folds with the specific activity of about 11.7 U/mg protein.Purity was perfonned using the polyacrylamide gel electrophoresis technique. The molecular weight of Ps was estimated to be 42,000 Dalton by SOS-PAGE and the isoelectric point was at pH 4.2. The manganese peroxidase was purfied by means of ammonium sulphate precipitation and gel filtration chromatography of Sephadex G-100 and agarose. The enzyme recovery of 40.9% was obtained, with about 16 folds with the specific activity of about 8.0 U/mg protein. The enzyme showed a broad band on SoS-PAGE which was considered partially purified. The decolourization of methylene blue, polyvinylamine sulfonate anthrapiridone (Poly R-478) and a waste water from a local textile industry revealed that the decolourization was related to the lignin peroxidase and manganese peroxidase formation in the growth medium. However, only lignin peroxidase was found responsible for the decolourization process. The decolourization rate and chemical oxygen demand (COD) reduction of the local waste waters occured during the secondary phase of the fungal growth and related to lignin peroxidase formation. The biodegradation of rice husks and oil palm trunk chips by P. chrysosporium and its ligninolytic enzymes were investigated. P. chrysosporium produced lignin peroxidase, manganese peroxidase, cellulase, xilanase and ~- glucosidase in the growth medium, with rice husks of oil palm trunk chips. as substrates in a SSF system. The ligninolytic degradation on rice husks enabled silica extraction be performed at lower temperature of 323°C. Similarly, the extraction of reducing sugar from oil palm trunk chips was highly improved by sequential treatment of acid, lignin peroxidase and cellulase hydrolysis. Under these optimum conditions, a maximum production of 78.6 g/g of reducing sugar was obtained.
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ENZIM PENGURAI , PHANEROCHAETE CHRYSOSPORIUM
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