Inline monitoring of fermentation processes

Importance of the Topic

Bioethanol derived from renewable biomass plays a key role in reducing dependence on fossil fuels. Fermentation processes convert sugars into ethanol, but fluctuations in feedstock quality and process conditions can affect yield and productivity. Inline near-infrared spectroscopy (NIRS) offers fast, reagent-free measurements directly in the fermentation tank, enabling real-time monitoring and control of critical parameters.

Objectives and Study Overview

This application note (AN-PAN-1057) demonstrates how Metrohm Process Analytics uses the 2060 The NIR Analyzer to track multiple fermentation quality markers simultaneously. The main goals are to reduce response time, minimize sampling errors, and optimize ethanol production by continuous measurement of key analytes without manual laboratory assays.

Methodology and Instrumentation

The inline system comprises the 2060 The NIR Analyzer coupled via microbundle fibers to immersion probes designed for slurries with suspended solids. A flow cell option can be used in a bypass loop to remove large particles prior to measurement. Calibration models were built using a representative set of fermentation samples analyzed by primary methods (HPLC, Karl Fischer titration) to cover the full concentration ranges of ethanol, sugars, organic acids, glycerol, moisture, and solids.

• Analyzer: Metrohm 2060 The NIR Analyzer, supporting up to five probe channels
• Sampling probes: micro-interactance reflectance and transmission probes for slurries and clear liquids
• Calibration references: high-performance liquid chromatography, ion chromatography, and Karl Fischer titration

Key Results and Discussion

Inline NIRS provided quantitative updates approximately every 30 seconds, capturing dynamic trends of ethanol formation and residual solids. Models for ethanol (0–15%), glucose (0–8%), maltose (0–7%), DP3/DP4 dextrins (0–15%), acetic acid (0–0.5%), glycerol (0–1%), and lactic acid (0–0.25%) exhibited strong correlation with laboratory assays. Real-time sugar tracking allowed timely enzyme and yeast adjustments, accelerating starch breakdown and improving overall yield. Reduced fermentation time led to additional batch cycles per day and increased profitability.

Benefits and Practical Applications

Inline NIRS monitoring delivers multiple advantages:

• Immediate feedback on process performance without sample preparation
• Improved safety by eliminating chemical reagents and manual handling
• Cost savings through fewer laboratory assays and faster decisions
• Enhanced throughput, reproducibility, and resource utilization

Future Trends and Applications

Advances in spectroscopy and chemometric algorithms will enable deeper integration of inline NIRS into automated process control systems and digital twins. Expanding applications to lignocellulosic feedstocks and continuous fermentation bioreactors will further improve biofuel sustainability. Connectivity to plant data networks and cloud analytics will support predictive maintenance and advanced product quality monitoring.

Conclusion

Metrohm’s inline NIRS solution with the 2060 The NIR Analyzer transforms ethanol fermentation monitoring by offering fast, accurate, and reagent-free measurements directly in the process line. The ability to track multiple analytes in real time empowers producers to optimize enzyme and yeast dosing, reduce cycle times, and maximize yields.

References

1. Statista. Global ethanol production for fuel use 2022. https://www.statista.com/statistics/274142/global-ethanol-production-since-2000/
2. Chang Y-H, Chang K-S, Chen C-Y et al. Enhancement of the Efficiency of Bioethanol Production by Saccharomyces cerevisiae via Gradually Batch-Wise and Fed-Batch Increasing the Glucose Concentration. Fermentation. 2018;4(2):45.
3. Devantier R, Pedersen S, Olsson L. Characterization of Very High Gravity Ethanol Fermentation of Corn Mash. Effect of Glucoamylase Dosage, Pre-Saccharification and Yeast Strain. Appl Microbiol Biotechnol. 2005;68(5):622–629.