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Metabolic Activity Profiling of High-Temperature Daqu Microbiota Using Single-Cell Raman Spectroscopy and Deuterium
Lei Xu1, Zhen-Ming Lu1,2,3, Xiao-Juan Zhang1,3
1School of Biotechnology, Key Laboratory of Industrial Biotechnology of Ministry of Education, Jiangnan University, Wuxi 214122, P. R. China.
Analytical Chemistry
|August 7, 2025
Summary
Assessing microbial metabolic activity in Daqu, crucial for baijiu production, is now possible with Raman-DIP. This method accurately classifies Daqu batches by microbial activity, enhancing baijiu quality and consistency.
Area of Science:
- Microbiology
- Analytical Chemistry
- Food Science
Background:
- Microbial metabolic activity in Daqu significantly impacts baijiu quality and consistency.
- Variability in Daqu batches, even within the same fermentation environment, necessitates robust assessment methods.
- Existing methods for evaluating Daqu's microbial activity are often destructive or lack in situ capabilities.
Purpose of the Study:
- To develop and validate an in situ, nondestructive method for assessing microbial metabolic activity in high-temperature Daqu at the single-cell level.
- To establish a classification system for high-temperature Daqu based on microbial metabolic activity patterns.
- To correlate microbial metabolic activity with key physicochemical properties relevant to baijiu brewing.
Main Methods:
- Raman microspectroscopy combined with deuterium isotope probing (Raman-DIP) was utilized to measure microbial metabolic activity.
- The deuterium incorporation ratio (C/D ratio) was used to quantify metabolic activity at the single-cell level.
- Partial least-squares analysis and a 2D-convolutional neural network (2D-CNN) model were employed for data analysis and classification.
Main Results:
- High-temperature Daqu samples were successfully classified into three microbial activity patterns (A-C) based on C/D ratio thresholds.
- Raman spectral phenotypes, particularly band intensities, differed among Daqu batches (PC-Daqu vs. PA-Daqu and PB-Daqu).
- A significant correlation was found between the C/D ratio, Raman characteristic peak intensities, and physicochemical properties like total acidity and enzyme activities.
- The developed 2D-CNN model achieved 99% accuracy in discriminating microbial activity patterns.
Conclusions:
- Raman-DIP offers a powerful tool for in situ, single-cell level assessment of high-temperature Daqu microbial metabolic activity.
- This method enables objective classification of Daqu batches according to their metabolic profiles, aiding in baijiu production control.
- The findings facilitate the selection of Daqu with specific functionalities to improve baijiu quality and production consistency.
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