Generation of Synechocystis sp. PCC 6803 mutant with enhanced laccase-like activity

Cyanobacteria offer a good alternative to fungi for laccase production at industrial scales. Random mutagenesis approaches with ethyl methanesulfonate were used in combination with enzymatic assays screenings to select a mutant of Synechocystis sp. PCC 6803, A2, with enhanced extracellular laccase-like activity. Anthraquinone dye decolourisation assays revealed 7 % enhanced decolourisation in A2 relative to the wild type after 24 h. The comparison of microbiome structure and diversity of the wild type and A2 strains confirmed that the improved traits were due to the mutation(s) and not the associated bacteria. The newly isolated Synechocystis mutant is the first example of successful random mutagenesis of cyanobacteria for laccase production. Attempts to characterise the biochemical reaction and putative laccase in A2 strain were unsuccessful but will be the subject of further research. This study suggests that random mutagenesis as a powerful approach for generating cyanobacterial strains with enhanced laccase-like activity for prospective commercial applications. [Display omitted] •Mutant with laccase-like activity of 0.10 U mL−1 obtained by random mutagenesis.•Mutant grew 1.5 times faster than WT with 10 times higher laccase-like activity.•Improved traits of the mutant were not due to associated bacteria but the mutations.•Mutant decolourised 14 % of RBBR after 3 h, which is double than WT.•This study shows industrial applicability of cyanobacterial extracellular laccases.