Biotechnology and Bioprocess Engineering 2019; 24(3): 488-499  
Production of 5-aminolevulinic Acid by Recombinant Streptomyces coelicolor Expressing hemA from Rhodobacter sphaeroides
Nu Thi Tran, Diep Ngoc Pham, and Chang-Joon Kim*
Department of Chemical Engineering and ERI, Gyeongsang National University, Jinju 52828, Korea
Correspondence to: Chang-Joon Kim*
Tel: +82-55-772-1787; Fax: +82-55-772-1789
E-mail: cj_kim@gnu.ac.kr
Received: December 16, 2018; Revised: May 7, 2019; Accepted: May 13, 2019; Published online: June 30, 2019.
© The Korean Society for Biotechnology and Bioengineering. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Over the past two decades, intensive efforts have been made to construct recombinant Escherichia coli or Corynebacterium glutamicum by engineering C4 or C5 pathways to improve microbial production of 5-aminolevulinic acid (ALA), which has medical application for photodynamic cancer therapy and tumor diagnosis. In this study, we explored the feasibility of enhanced production of ALA by expressing C4 pathway enzyme, ALA synthase, in Streptomyces coelicolor, and medium optimization. The hemA from Rhodobacter sphaeroides was successfully integrated into the chromosome of Streptomyces coelicolor by conjugal transformation, and recombinant Streptomyces cells expressed well the foreign hemA. Glucose promoted ALA synthesis, and yeast extract showed a strong positive effect on ALA production. Optimization of casamino acid, peptone, malt extract, glycine, and succinic acid increased the product titer. In flask cultures, cell growth and ALA production of recombinant Streptomyces were 2.3 and 3.0-fold higher, respectively, in optimal medium than those of control. The maximum ALA, 137 mg/L, was obtained at 28 h in bioreactor culture, in which 3.1-fold higher cell mass and 2.9-fold greater volumetric productivity were achieved, compared to those in flask cultures.
Keywords: recombinant Streptomyces coelicolor, C4 pathway, hemA overexpression, 5-aminolevulinic acid, medium optimization


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