Transgenic plant cell suspension culture is a promising platform for recombinant protein production. Rice cell suspension culture is one of the systems that has been developed due to its unique metabolically-regulated promoter, rice alpha-amylase 3D (RAmy3D), that is up-regulated in sugar-deprived medium. Using the RAmy3D promoter system in transgenic rice cell suspensions results in two phases of the culture, the growth phase and the induction phase. Conventionally, medium exchange is performed to remove residual sugar and induce recombinant protein. In this work, a simplified production process is demonstrated in a 5-L bioreactor, including reduction of sugar concentration in the initial culture medium, elimination of the media exchange operation, and uncontrolled dissolved oxygen (DO) with constant aeration. The simplified method significantly improves the accumulation level of a recombinant protein, protein purity, and productivity compared to the conventional method. This method also reduces costs associated with material and labor. • The method of simplified bioreactor processing includes single-stage culture, uncontrolled dissolved oxygen (DO) but controlled inlet air flowrate, and lower (50% reduction) initial sucrose concentration in the culture medium. • This method improves recombinant protein production level and productivity compared to the conventional method. • This method reduces material and labor costs.