Production of ferulic acid from lignocellulolytic agricultural biomass by Thermobifida fusca thermostable esterase produced in Yarrowia lipolytica transformant

A gene (axe) encoding the AXE thermostable esterase in Thermobifida fusca NTU22 was cloned into a Yarrowia lipolytica P01g host strain. Recombinant expression resulted in extracellular esterase production at levels as high as 70.94 U/ml in Hinton flask culture broth, approximately 140 times higher than observed in a Pichia pastoris expression system. After 72 h of fermentation by the Y. lipolytica transformant in the fed-batch fermentor, the fermentation broth accumulated 41.11 U/ml esterase activity. Rice bran, wheat bran, bagasse and corncob were used as hydrolysis substrates for the esterase, with corncob giving the best ferulic acid yield. The corncob was incubated with T. fusca xylanase (Tfx) for 12 h and then with the AXE esterase for an additional 12 h. Ferulic acid accumulated to 396 μM in the culture broth, a higher concentration than with esterase alone or with Tfx and esterase together for 24 h.