关键词: laccase isozyme, Pestalotiopsis sp., marine microorganism, carbon and nitrogen source, inducer

Abstract: Pestalotiopsis sp. J63, producing a high activity of laccase, is a new marine-derived fungus isolated from the oceanic sediment of the East China Sea. Since the marine environment is oligotrophic nutrient, marine derived fungi may use small amount of nutrients to grow and produce laccases. Agricultural residues that are mainly composed of lignin, cellulose and hemicellulose are difficult to be degraded and few microbes can take them as substrates, so they are considered as oligotrophic nutrient and have the potential to be used to produce value added products. In this study, the ability of Pestalotiopsis sp. J63 to use agricultural residues to produce laccases was tested in the submerged fermentation. The combination of 3 g·L^-1 maltose and 20 g·L^-1 rice straw was the best carbon sources and 8 g·L^-1 ammonium sulfate was the best nitrogen source under the condition without inducers. The effects of five inducers, the feeding time and concentration of inducer on laccase production were investigated. Adding 0.09 mmol·L^-1 phenol after 24 h of incubation led to high laccase activity (5089 U·L^-1), while with 0.09 mmol·L^-1 phenol in the medium and wheat bran as the nitrogen source, the laccase activity could reach 5791.7 U·L^-1. Native-PAGE results showed that two laccase isozymes were present in the cultures. One existed in both induced and non-induced culture filtrates, while the other was only found in the fermentation with the addition of phenol, guaiacol and veratryl alcohol.

Key words: laccase isozyme, Pestalotiopsis sp., marine microorganism, carbon and nitrogen source, inducer