Enhanced Production of Carboxymethylcellulase by Recombinant Escherichia coli Strain from Rice Bran with Shifts in Optimal Conditions of Aeration Rate and Agitation Speed on a Pilot-Scale

Chung-Il Park,Jin-Woo Lee,Jae-Hong Lee,Jianhong Li

doi:10.3390/app9194083

Chung-Il Park, Jin-Woo Lee + Show 2 more

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https://doi.org/10.3390/app9194083

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Abstract

The optimal conditions including the aeration rate and agitation speed of bioreactors for the production of carboxymethylcellulase (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.

Highlights

Lignocellulosic agricultural byproducts rich in complex carbohydrates can be used as renewable feed-stocks for the production of monomeric sugars for fermentation by physicochemical and enzymatic degradations [1]
Bioreactor for the cell growth of E. coli KACCP 91335P and its production of CMCase were optimized using the response surface methodology based on the cell growth measured as DCW and produced
Owing to the mixed-growth-associated production of CMCase by E. coli Korean Agricultural Culture Collection (KACC) 91335P, shifts in the optimal conditions of the aeration rate and/or agitation speed from the cell growth to its production of CMCase at the mid-log phase of cell growth resulted in relatively higher cell growth, which in turn enhanced the production of CMCase

Summary

Introduction

Lignocellulosic agricultural byproducts rich in complex carbohydrates can be used as renewable feed-stocks for the production of monomeric sugars for fermentation by physicochemical and enzymatic degradations [1]. At least three types of cellulases are required; endocellulases, exocellulases and cellobiases [2]. Endocellulases (EC 3.2.1.4) break the noncovalent interactions present in the amorphous structure of cellulose, exocellulases (EC 3.2.1.91) hydrolyze chain ends to break the polymer into smaller sugars and cellobiases (EC 3.2.1.21) hydrolyze disaccharides and tetrasaccharides into glucose [3]. The carboymethylcellulase (CMCase) is a type of endocellulase, which is the major cellulase in the conversion of cellulose [2]. The high cost and low productivity of cellulases are drawbacks to overcome the enzymatic saccharification of lignocellulosic materials [4]. Many studies on the types of strains including recombinants, substrates and cultural conditions for the enhanced production of cellulases have been reported [5,6]

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