_Applied_  
_sciences_  
_Article_  
**Enhanced Production of Carboxymethylcellulose by Recombinant _Escherichia coli_ Strain from Rice Bran with Shifts in Optimal Conditions of Aeration Rate and Agitation Speed on a Pilot-Scale**  
**[PERSON] 1, [PERSON] 2, [PERSON] 3 and [PERSON] 1,2,4,*(c)**  
1 Department of Applied Bioscience of Graduate School, Dong-A University, Busan 49315, Korea; [PERSON]RESS]  
2 Department of Biotechnology of Graduate School, Dong-A University, Busan 49315, Korea; [EMAIL_ADDRESS]  
3 College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; [EMAIL_ADDRESS]  
4 Department of Biotechnology, College of Life Science and Natural Resources, Dong-A University, Busan 49315, Korea  
* Correspondence: [EMAIL_ADDRESS]; Tel.: +82-51-200-7593  
Received: 3 September 2019; Accepted: 27 September 2019; Published: 30 September 2019  
**Featured Application: The simple and economical process with shifts in optimal conditions of the aeration rate and agitation speed of a pilot-scale bioreactor from the cell growth to its production at the mil-log phase was developed for the industrial-scaled mass production of cellulases.**  
**Abstract: The optimal conditions including the aeration rate and agitation speed of bioreactors for the production of carboxymethylcellulose (CMCase) by a recombinant _Escherichia coli_ KACC 91335P, expressing CMCase gene of _B. velezensis_ A-68, were different from those for its cell growth. The enhanced production of CMCase by _E. coli_ KACC 91335P with the conventional multistage process needs at least two bioreactors. Shifts in the optimal conditions of the aeration rate and agitation speed of the bioreactor from the cell growth of _E. coli_ KACC 91335P to those for its production of CMCase were investigated for development of the simple and economic process with the high productivity and low cost. The production of CMCase by _E. coli_ KACC 91335P with shifts in the optimal conditions of the aeration rate and agitation speed from the cell growth to its production of CMCase in a 100 L pilot-scale bioreactor was 1.36 times higher than that with a fixed optimal conditions of the aeration rate and agitation speed for the production of CMCase and it was even 1.54 times higher than that with a fixed optimal conditions of the aeration rate and agitation speed for cell growth. The best time for the shift in the optimal conditions was found to be the mid-log phase of cell growth. Owing to the mixed-growth-associated production of CMCase by _E. coli_ KACC 91335P, shifts in the optimal conditions of the aeration rate and agitation speed of bioreactors from the cell growth to its production of CMCase seemed to result in relatively more cells for the participation in its production of CMCase, which in turn enhanced its production of CMCase. The process with a simple control for shifts in the aeration rate and agitation speed of a bioreactor for the enhanced production of CMCase by _E. coli_ KACC 91335P on the pilot-scale can be directly applied to the industrial-scaled production of cellulase.  
**Keywords: aeration rate; agitation speed; carboxymethylcellulose; _Escherichia coli_ KACC 91335P; pilot scale; rice bran