title: A simple method to monitor and control methanol feeding of Pichia pastoris fermentations using mid-IR spectroscopy.
abstract: Mid-infrared FTIR spectroscopy is an efficient tool for the monitoring of bioprocesses, since it is fast and able to detect many compounds simultaneously. However, complex and time-consuming calibration procedures are still required, and have inhibited the spreading of these instruments. A simple and quick method to calibrate a FTIR instrument was developed for the control of fed-batch fermentations of the methylotrophic yeast Pichia pastoris. Based on the assumptions that (1) only substrate concentration may change significantly during a fed-batch process and (2) absorbance can be considered as proportional to concentration, a linear two-point calibration was implemented. Long-term instability of the instrument had to be addressed in order to get accurate results: two fixed points, on both sides of substrate absorbance peak, were used to perform on-line a linear correction of the signal drift. Fed-batch experiments at constant methanol (substrate) concentration ranging from 0.8 to 15gl(-1) were carried out. Off-line HPLC control analysis showed a good agreement with on-line FTIR data, with standard error of prediction values < 0.12gl(-1). Even though methanol acts both as carbon source and inducer of protein expression, no significant effect was observed on the level of protein expression in the recombinant strain used.
authors.affiliation: Laboratory of Chemical and Biochemical Engineering (LGCB), Station 6-CH J2 503, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
authors.forename: Jonas
authors.initials: J
authors.lastname: Schenk
authors.forename: Ian W
authors.initials: IW
authors.lastname: Marison
authors.forename: Urs
authors.initials: U
authors.lastname: von Stockar
mesh_terms: D019149:Bioreactors; D002138:Calibration; D005285:Fermentation; D000432:Methanol / Q000032:analysis* / Q000378:metabolism; D010843:Pichia / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared / Q000295:instrumentation / Q000379:methods
chemical_list: D000432:Methanol