We observed that an inclusion body (IB) of recombinant ${eta}$-galactosidase that was produced by the araBAD promoter system in Escherichia coli (E. coil) showed enzyme activity. In order to improve its activity, the lowering of the transcription rate of the ${eta}$-galactosidase structural gene was attempted through competition between an inducer (L-arabinose) and an inducer analog (D-fucose). In the deep-well microtiter plate culture and lab-scale fermentor culture, it was demonstrated that the addition of D-fucose caused an improvement in specific ${eta}$-galactosidase production, although ${eta}$-galactosidase was produced as an IB. In particular, the addition of D-fucose after induction led to an increase in the specific activity of ${eta}$-galactosidase IB. Finally, we confirmed that the addition of D-fucose after induction caused changes in the structure of ${eta}$-galactosidase IB, with higher enzyme activity. Based on these results, we expect that an improved enzyme IB will be used as a biocatalyst of the enzyme bioprocess, because an enzyme IB can be purified easily and has physical durability.