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Removing the by-products acetic acid and NH4 + from the L-tryptophan broth by vacuum thin film evaporation during L-tryptophan production
Xu, Qingyang; Bai, Fang; Chen, Ning; Bai, Gang.
  • Xu, Qingyang; Nankai University. Tianjin Key Laboratory of Molecular Drug Research. Tianjin. CN
  • Bai, Fang; Nankai University. Tianjin Key Laboratory of Molecular Drug Research. Tianjin. CN
  • Chen, Ning; Tianjin University of Science and Technology. College of Biotechnology. Tianjin. CN
  • Bai, Gang; Nankai University. Tianjin Key Laboratory of Molecular Drug Research. Tianjin. CN
Electron. j. biotechnol ; 33: 46-51, May. 2018. ilus, graf
Article in English | LILACS | ID: biblio-1022928
ABSTRACT

Background:

During L-tryptophan production by Escherichia coli, the by-products, acetic acid and NH4 +, accumulate in the fermentation broth, resulting in inhibited cell growth and activity and decreased L-tryptophan production. To improve the L-tryptophan yield and glucose conversion rate, acetic acid and NH4 + were removed under low-temperature vacuum conditions by vacuum scraper concentrator evaporation; the fermentation broth after evaporation was pressed into another fermenter to continue fermentation. To increase the volatilisation rate of acetic acid and NH4 + and reduce damage to bacteria during evaporation, different vacuum evaporation conditions were studied.

Results:

The optimum operating conditions were as follows vacuum degree, 720 mm Hg; concentration ratio, 10%; temperature, 60°C; and feeding rate, 300 mL/min. The biomass yield of the control fermentation (CF) and fermentation by vacuum evaporation (VEF) broths was 55.1 g/L and 58.3 g/L at 38 h, respectively, (an increase of 5.8%); the living biomass yield increased from 8.9 (CF) to 10.2 pF (VEF; an increase of 14.6%). L-tryptophan production increased from 50.2 g/L (CF) to 60.2 g/L (VEF) (an increase of 19.9%), and glucose conversion increased from 18.2% (CF) to 19.5% (VEF; an increase of 7.1%). The acetic acid concentrations were 2.74 g/L and 6.70 g/L, and the NH4 + concentrations were 85.3 mmol/L and 130.9 mmol/L in VEF and CF broths, respectively.

Conclusions:

The acetic acid and NH4 + in the fermentation broth were quickly removed using the vacuum scraper concentrator, which reduced bacterial inhibition, enhanced bacterial activity, and improved the production of L-tryptophan and glucose conversion rate.
Subject(s)


Full text: Available Index: LILACS (Americas) Main subject: Tryptophan / Acetic Acid / Amino Acids Language: English Journal: Electron. j. biotechnol Journal subject: Biotechnology Year: 2018 Type: Article Affiliation country: China Institution/Affiliation country: Nankai University/CN / Tianjin University of Science and Technology/CN

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Full text: Available Index: LILACS (Americas) Main subject: Tryptophan / Acetic Acid / Amino Acids Language: English Journal: Electron. j. biotechnol Journal subject: Biotechnology Year: 2018 Type: Article Affiliation country: China Institution/Affiliation country: Nankai University/CN / Tianjin University of Science and Technology/CN