Enhancing Production of Tryptophan via Cellulose Utilization by Escherichia coli.

Biorefinery and microbial production from waste and renewable materials has generated a lot of attention nowadays. Among these candidates, cellulose is a promising alternative energy source to petroleum chemicals. However, the utilization of cellulose by Escherichia coli faces challenges Soluble expression and enzyme release process limit the use of cellulose by E. coli. In this study, we applied a genetic circuit which contains both cellulose expression module and cell lysis module to accomplish expression and release process simultaneously. Expression of endo-1,4-beta-glucanase (cel5) and colicin E7 is under control of T7 promoter and pBAD promoter separately. After retransformation genetic circuit and Congo red plate screening, the cellulase activity of lysis supernatant reached 4.43 U/mL, which was 16.47-fold higher than that of the sonication supernatant. Using self-lysis supernatant and cellulose mixture as additional carbon source, the tryptophan production increased 28.4% compared to the control group, the maximum production reached 429.45 mg/L. The simultaneous expression and release circuit was first applied in metabolite production. This result provided a feasible strategy of using cellulose to enhance the performance of E. coli.