Engineering Escherichia coli Biofilms for Curcumin Production

Biofilms are emerging platforms for the production of valuable compounds. The present study is the first to assess the capacity of <i>Escherichia coli</i> biofilms to produce curcumin through the expression of a biosynthetic pathway involving three genes: 4-coumarate-CoA ligase (<i>4CL</i>), diketide-CoA synthase (<i>DCS</i>), and curcumin synthase (<i>CURS</i>). The effects of chemical induction with isopropyl β-d-1-thiogalactopyranoside (IPTG) and ferulic acid (FA), and the incubation temperature on biofilm formation and curcumin production were evaluated. Biofilms were formed in 12-well microtiter plates over three days and then induced with 1 mM IPTG and FA at 2 or 8 mM. After induction, the samples were incubated for two days at 26 or 30 °C. Total and culturable planktonic and biofilm cells, as well as biofilm thickness and volumetric and specific curcumin production, were assessed on days 3, 4, and 5. The results demonstrated that biofilms produced up to 10-fold higher curcumin levels (0.9-2.2 fg·cell^-1) than their planktonic counterparts (0.1-0.3 fg·cell^-1). The highest specific curcumin production (2.2 fg·cell^-1) was achieved using 8 mM FA. However, no significant differences in curcumin production were observed between the induced samples incubated at the tested temperatures. These results validated the potential of biofilm systems for expressing a complete exogenous biosynthetic pathway using metabolic engineering, particularly for curcumin production.