Fig. 2

Screening results of three cycles of random mutagenesis (a); saturation mutagenesis at residues L141, Y195, and W256 (b); and critical amino acid substitutions by site-directed mutagenesis (c). a Twenty representative strains are shown for each sequential mutagenesis step. The average relative lycopene production of the mutants increased progressively with every round of mutagenesis. Strains with the highest relative lycopene production in each round were chosen for further analysis. b Twenty representative strains are shown for every position to identify the most advantageous amino acid substitution at these residues. These same colour columns represent different residual activities at the same position. c Single, double and triple mutation enzymes were constructed to determine which were sufficient and necessary for enhanced IDI activity. Every mutant was necessary for IDI and worked well with no interference. Wild-type IDI was used as the control (OD^*₄₇₅)