Hansen K F, Lauritsen F R, Degn H
Institute of Biochemistry, Odense University, DK-5230 Odense M, Denmark.
Biotechnol Bioeng. 1994 Jul;44(3):347-53. doi: 10.1002/bit.260440312.
A sampling system for on-line monitoring of organic compounds of low volatility in complex fermentation media uses membrane inlet mass spectrometry (MIMS). A Syringe pump draws a continuous flow of microfiltered broth from the reactor and circulates it after acidification through a membrane inlet, in which a membrane is the only interface between the sample and the high vacuum of a mass spectrometer. All operations run automatically, i.e., sampling, acidification measurement, and calibration. The on-stream acidification enables MIMS monitoring of carboxylic acids, as they must be undissociated in order to pass the hydrophobic membrane. The performance of the monitoring system was tested by measurements of standard solutions of phenoxyacetic acid (POAA, the sie chain precursor of penicillin-V) as well as on POAA during 200 h penicillin-V fermentation. During the entire fermentation POAA was monitored n low millimolar concentrations with high accuracy and fast response to step changes in POAA concentration. Tandem mass spectrometry (MS/MS) allowed direct identification of peaks in the mass spectrum of the broth that were not accounted for by POAA. These peaks were identified as SO(2) and SCO.
一种用于在线监测复杂发酵培养基中低挥发性有机化合物的采样系统采用了膜进样质谱法（MIMS）。注射泵从反应器中抽取连续流动的微滤肉汤，在酸化后使其通过膜进样口循环，其中膜是样品与质谱仪高真空之间的唯一界面。所有操作均自动运行，即采样、酸化测量和校准。在线酸化使得MIMS能够监测羧酸，因为它们必须处于未离解状态才能通过疏水膜。通过测量苯氧乙酸（POAA，青霉素V的侧链前体）标准溶液以及在200小时青霉素V发酵过程中对POAA的测量，测试了监测系统的性能。在整个发酵过程中，以低毫摩尔浓度高精度监测POAA，并对POAA浓度的阶跃变化做出快速响应。串联质谱法（MS/MS）能够直接识别肉汤质谱图中未被POAA解释的峰。这些峰被鉴定为SO(2)和SCO。
