Production of Laccase by Alternaria alternata and Lasiodiplodia theobromae

Laccase is a copper-containing polyphenol oxidase that acts on a wide range of substrates. This enzyme is found in many plant species and is widely distributed in fungi including wood-rotting fungi where it is often associated with lignin peroxidase, manganese dependent peroxidase, or both. Because of its importance in bioremediation, fungal cultures were screened for laccase positive production by plate test method using the indicator compound guaiacol. The biotechnological application of laccase has been expanded by the introduction of laccase- mediator systems, which are able to oxidize non-phenolic compounds that are otherwise not attacked and are thus able to degrade lignin in kraft pulps. Both cultures were found to be laccase-positive with Alternaria alternata and Lasiodiplodia theobromae being the best potential cultures. Laccase activity was determined using ABTS as substrate. Higher level of laccase activity was observed by Alternaria alternata (3.221U/ml) than that of Lasiodiplodia theobromae (2.318 U/ml). Laccase was purified by Ammonium sulfate salt saturation, dialysis and gel filtration chromatography. The purified laccase was a monomer showed a molecular mass of 45±1kDa as estimated by SDSPAGE and a 4.02-fold purification with a 2% yield