This year our project focused on enhancing the growth and production efficiency of the engineered bacteria during high-density fermentation. Previous research has found that expressing Vitreoscilla hemoglobin (VHb) inside the bacteria could leverage its property of combining and releasing oxygen to improve the efficiency of oxygen utilization and therefore enhance the efficiency of bacteria growth and production. Follow-up studies have shown that expressing VHb in the periplasmic space could further improve that efficiency compared with intracellular expression. Based on these, we proposed that expressing VHb outside the outer membrane using surface display system could further enhance the oxygen density surrounding the bacteria and improve oxygen utility in the system for further enhancement of the fermentation efficiency.
Surface display system
Our project used three different surface display system including INP (BBa_K523013), intimin and autotransporter. We fused these surface transporter proteins with fluorescent protein meos and sfGFP respectively and observed the bacteria carrying these plasmids under confocal microscope to confirm that these systems could work effectively.
We compared the growth efficiency of E.coli BL21 expressing VHb in the cell and on cell surface respectively mainly using the following parts.
1.Lei Zhang et al.. Recent developments and future prospects of Vitreoscilla hemoglobin application in metabolic engineering. Biotechnology Advances 25(2007).
2.Pengfei Ouyang et al.. Increasing oxygen availability for improving poly(3-hydroxybutyrate) production by Halomonas. Metabolic Engineering 45(2018).