Abstract
Mixing cultures induces the biosynthesis of laccase in mixed cells, produces signal molecules, and regulates the production of mixed-cell metabolites. The fungal strain, which promotes laccase production, has been isolated and screened from the host bamboos of endophytic fungi and identified as Phoma sp. BZJ6. When the culture medium is mainly composed of soluble starch, yeast extract, and Phoma sp., the laccase output can reach 4,680 U/L. Nitric oxide (NO) and reactive oxygen species (ROS) were found to promote the regulation of laccase synthesis. Plasma membrane NAD(P)H oxidase inhibitors and NO-specific quenchers can inhibit not only the accumulation of ROS induced and NO synthesis but also the biosynthesis of laccase. The results indicate that the accumulation of superoxide anion radical (O(2)(-)) and hydrogen peroxide (H(2)O(2)) induced by the mixed culture was partially dependent on NO. The mixed culture can also reduce the biomass, increase the synthesis of total phenolics and flavonoids, and enhance the activity of phenylalanine ammonia-lyase and chalcone isomerase. This phenomenon is probably the result of the activated phenylpropanoids-flavonoid pathway. Results confirmed that the mixture culture is advantageous for laccase production and revealed that NO, O(2)(-), and H(2)O(2) are necessary signal molecules to induce laccase synthesis.