Impact of NH4+ Nitrogen Source on the Production of Rhizopus chinnensis Lipase by Pichia pastoris

Abstract:

The effect of NH4+ concentration on the expression of Rhizopus chinensis lipase by the recombinant Pichia pastoris was studied by high-density fed-batch fermentation in a 7 L bioreactor. The maximum activity was obtained when the concentration of NH4+ was maintained at 7 g/L adjusted with （NH4）2SO4 solution，as high as 1.41，1.11，1.08 fold of that of the control （without （NH4）2SO4 solution），and of the solution with 5 g/L or 10 g/L NH4+，respectively. The total protein concentration achieved a maximum value of 5.61 g/L under the optimal condition. The specific growth rate，the specific production rate and the specific consumption rate were also investigated under different NH4+ concentrations. A relative high specific production rate and the specific consumption rate were observed at 7 g/L of NH4+，which resulted in the highest level of enzyme production under the condition. Our research suggested that the optimization of nitrogen source could enhance the expression of heterologous protein significantly in P. pastoris.