Correlation analysis for non-invasive quantitative monitoring of biological activity of recombinant enzyme using green fluorescence protein in Escherichia coli under various culture environments

Monitoring of biological activity for target enzyme is important for its production in recombinant expression systems. Previously, we demonstrated that green fluorescent protein (GFP) as a fusion partner is successfully tooled for facile, in vivo, and non-invasive quantification of target enzyme levels based on a linear relationship between GFP fluorescence and enzyme (chloramphenicol acetyltransferase; CAT) activity. Here, we investigated the effects of culture environmental variations (initial glucose amount, surface aeration, and inducer concentration) on correlation between GFP fluorescence and CAT activity, and established a general linear correlation as a unique criterion for quantitative monitoring of CAT biological activity. This general correlation for GFP fusion strategy can be applied for non-invasive and on-line monitoring of recombinant enzyme production under various culture conditions without further experimental calibrations.