Comprehensive Quality Evaluation of Corn Steep Liquor in 2-Keto-L-gulonic Acid Fermentation

Corn steep liquor (CSL) is one of the main raw materials in 2-keto-L-gulonic acid (2-KLG) fermentation by Ketogulonicigenium vulgare and Bacillus megaterium. Due to its natural origin and variations in the manufacturing process, unpredicted and uncontrolled variability of CSL has a great influence on 2-KLG production; however, conventional quality specifications are not enough to ensure stability of fermentation behaviors. A process analytical technology (PAT) could be considered to explore the relationship between CSL quality and 2-KLG production comprehensively. The compositions of CSL from six manufacturers were profiled by gas chromatography with time-of-flight mass spectrometry (GC-TOFMS) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES), combined with orthogonal partial least-squares discriminant analysis (OPLS-DA). Seventeen components were identified as the most discriminant marker compounds related to 2-KLG production. Results revealed that they were responsible for providing nutrients and protecting osmotic pressure. Furthermore, nine amino acids were verified as potential group markers by addition to the medium and demonstration of the correlation to 2-KLG production. The comprehensive approach provided an important platform to explore CSL marker compounds for quality evaluation in 2-KLG fermentation.