Screening and Efficacy Evaluation of High-Yielding Manganese Peroxidase Strain

Background: Lignocellulose resources are abundant, but the utilization of lignocellulose is seriously hindered by the existence of lignin. Microorganisms rely on lignin-degrading enzymes to degrade lignin efficiently, so screening strains with high-yielding lignin-degrading enzymes will surely lay the foundation for the full utilization of lignocellulose. Objective: Therefore, this study expects to screen strains with high production of manganese peroxidase by effective means, and conduct preliminary evaluation of their efficacy. Methods: First, the strains with high production of manganese peroxidase were first screened by aniline blue medium; then some strains that produced decolorized transparent circles were screened again by enzyme activity assay, so as to screen out the strains with high production of manganese peroxidase (Take P. chrysosporium as the control); observe the growth state of the strain and identify the strain; the enzyme activity was further improved by optimizing the fermentation medium; finally, the enzyme properties were analyzed to evaluate the stability of manganese peroxidase. Results: In this study, a strain (L7) with high production of manganese peroxidase was successfully screened through primary screening and re-screening. After 6 days of fermentation, its enzyme activity was as high as 39.63 U/mL. On PDA solid medium, the strain was a light brown, round colony with brittle and slender mycelia, and it was identified as Fusarium proliferatum. The optimization test of fermentation medium showed that the highest activity of manganese peroxidase was 46.06 IU/mL under the conditions of glucose 10 g, beef extract 10 g, pH 6.5 and rotation speed 100 r/min. The analysis of enzymatic properties showed that the optimum reaction temperature of manganese peroxidase in this study was 20–40 ℃; When the pH is between 4.8–5.6, the stability of manganese peroxidase is good; Cu²⁺, Fe²⁺, Mn²⁺ can promote the activity of manganese peroxidase in this study, while K²⁺ has obvious inhibition, which can reach 95.346%. The strain screened in this study had not only high manganese peroxidase activity and enzyme production efficiency, but also had stable properties, therefore it is very valuable and worthy for further development and utilization. As one of the key enzymes in lignin degradation, it will certainly provide new ideas for the efficient utilization of biomass resources also.