Lower Temperature Cultures Enlarge the Effects of Vitreoscilla Hemoglobin Expression on Recombinant Pichia pastoris

An heterologous expression of Vitreoscilla hemoglobin (VHb) for improving cell growth and recombinant protein production has been successfully demonstrated in various hosts, including Pichia pastoris. Lower temperature cultures can enhance target protein production in some studies of P. pastoris. In this study, the strategy of combining heterologous VHb expression and lower temperature cultures in P. pastoris showed that final cell density and viability of VHb(+) strain at 23 degrees C were higher than that at 30 degrees C. In addition, the effects of VHb expression on recombinant beta-galactosidase production and oxygen uptake rate were also higher at 23 degrees C than at 30 degrees C. Consequently, lower temperature cultures can enlarge VHb effectiveness on cell performance of P. pastoris. This is because VHb activity obtained at 23 degrees C cultures was twofold higher than that at 30 degrees C cultures, due to a different heme production. This strategy makes P. pastoris an excellent expression host particularly suitable for increasing the yields of the low-stability and aggregation-prone recombinant proteins.