Abstract: In this study, the microbial strain designated as ZH-5 and capable of producting laccase was isolated from soil by plate chromogenic method and identified asSerratia marcescensby 16S rDNA and physiological and biochemical characteristics. Genome sequencing results showed that the genome size of strain ZH-5 was 5055904 bp, with GC content accounted for 59.55%, 4643 genes, and a total coding length of 4423485 bp, accounting for 87.49% of the genome. The genome contained a laccase gene (GE001633) and several heterologous biomass-degradation pathways. The enzyme reaction system was optimized firstly. The medium components of carbon and nitrogen sources were optimized further through single-factor optimization and orthogonal experiments. Based on single-factor and enzyme-catalyzed reaction system optimization, the medium composition was optimized through orthogonal experiments combining carbon and nitrogen sources. After 6 days of cultivation, the ZH-5 strain produced laccase activity of (24.68±0.76) U/mL in modified LB liquid medium containing 1 mmol/L Cu2+, 20 g/L peptone, 10 g/L yeast powder, and 20 g/L glycerol, representing a 34.74-fold increase compared to pre-optimization levels. In addition, the growth characteristics of ZH-5 were measured. The results showed that ZH-5 had better acid and salt tolerance and a broader temperature range for growth. Through the whole genome sequencing and gene function analysis of ZH-5, the activity of laccase was fully characterized, providing a theoretical basis for the subsequent application research based on ZH-5 laccase.

Key words: strain isolation;Serratia marcescens, laccase, enzyme activity, genome sequencing