Evaluation of an electrochemical bioreactor system in the biotransformation of 6-bromo-2-tetralone to 6-bromo-2-tetralol.
Biotransformation of 6-bromo-2-tetralone (Br-beta-tetralone) to 6-bromo-2-tetralol (Br-beta-tetralol) by yeast cells of Trichosporon capitatum (ATCC 74312) and its partially purified Br-beta-tetralone reductase was evaluated in an electrochemical bioreactor. The biotransformation rates and final product formation were significantly affected by substrate concentration, biomass and electric potential. At 2 g/l of substrate, the initial reaction rate and final product were increased by 35% and 15%, respectively, with -1.5 V of electric potential compared to without electric potential. Additional substrate (2 g/l) provided by pulse feeding to the reaction mixture at different intervals resulted in 2.1 g/l Br-beta-tetralol compared to a total of 1.2 g/l without feeding. However, the increased production was not proportionate to the amount of additionally fed substrate. Increased substrate availability by the addition of 5% (v/v) ethanol resulted in the highest reaction rate and product formation, but addition of ethanol at a concentration higher than 5% decreased the reaction rate. At low biomass, the initial reaction rates were enhanced significantly when electric potential was high, but a higher biomass was necessary to obtain a similar reaction rate when electric potential was reduced. The highest initial reaction rate (59.2 mg/l per min) was achieved with a two-fold biomass concentration of 15.6 g of dry cell weight/l, substrate at 4 g/l and electric potential at -6 V. The conversion of Br-beta-tetralone to Br-beta-tetralol with partially purified Br-beta-tetralone reductase was slow in the presence of electric potential.
Shin
H S
HS
MBI International, Lansing, MI 48909, USA.
Jain
M K
MK
Chartrain
M
M
Zeikus
J G
JG
D018533:Biomass; D019149:Bioreactors; D001711:Biotransformation; D004563:Electrochemistry; D000431:Ethanol / Q000494:pharmacology; D009281:Naphthalenes / Q000378:metabolism*; D044024:Tetralones; D014250:Trichosporon / Q000378:metabolism*
D009281:Naphthalenes; D044024:Tetralones; D000431:Ethanol; C009423:beta-tetralone