Quality Control of fermentation processes

Importance of the Topic

Ethanol fermentation from renewable feedstocks is a cornerstone of sustainable biofuel production. Reliable monitoring of this process ensures consistent product quality despite variations in feedstock composition and supports cost reduction in large‐scale operations.

Objectives and Study Overview

This application note evaluates the use of near‐infrared (NIR) spectroscopy for rapid, multiparameter quality control during corn‐based ethanol fermentation. A total of 206 mash samples were analyzed to develop predictive models for key process variables.

Methodology and Instrumentation

• Sample Type: Corn starch mash with high solid content
• Analyzer: DS2500 Solid Analyzer (400–2500 nm) in diffuse reflection mode
• Sample Holder: DS2500 Large Sample Cup with rotational scanning to average spatial heterogeneity
• Software: Vision Air Complete for spectral acquisition, preprocessing, and chemometric model building

Main Results and Discussion

The NIR calibration models demonstrated strong performance for most fermentation parameters:

• Ethanol content: R² 0.998, SEC 0.21 %, SECV 0.22 %
• Solid content: R² 0.982, SEC 0.87 %, SECV 1.06 %
• Brix index: R² 0.987, SEC 0.66, SECV 0.87
• Total sugar: R² 0.981, SEC 1.09 %, SECV 1.30 %
• Glucose: R² 0.920, SEC 0.70 %, SECV 0.86 %
• Maltotriose: R² 0.928, SEC 0.36 %, SECV 0.42 %
• Dextrin: R² 0.964, SEC 0.60 %, SECV 0.68 %
• Lactic acid: R² 0.722, SEC 0.09 %, SECV 0.10 %
• pH value: R² 0.734, SEC 0.17, SECV 0.19

High correlation for ethanol, solids, sugars, and carbohydrates confirms NIR reliability. Lower R² for lactic acid and pH highlights challenges in spectroscopic prediction of minor or highly variable components. Averaging spectra from multiple sample positions effectively reduced inhomogeneity effects.

Benefits and Practical Applications

• Sub‐minute, single‐scan measurement of multiple analytes
• Streamlines process control by replacing several reference methods
• Improves laboratory throughput and reduces operational costs
• Enables at‐line or in‐line integration for real‐time monitoring

Time‐to‐result comparison:

1. HPLC (ethanol, sugars): 30–45 min
2. Refractometer (Brix): 3–5 min
3. pH meter: 3–5 min
4. LO-D balance (solids): 10–15 min
5. NIR multiparameter: < 1 min

Future Trends and Potential Applications

• Continuous at‐line and in‐line NIR probe deployment for fermentation reactors
• Machine‐learning and advanced chemometrics for minor‐component quantification
• Portable and handheld NIR devices for decentralized quality checks
• Integration with digital twins and automated process control systems

Conclusion

NIR spectroscopy on the DS2500 Solid Analyzer offers a rapid, accurate, and comprehensive solution for monitoring ethanol fermentation. Its high predictive performance and minimal sample preparation position it as a valuable tool for modern bioprocess quality assurance.

Reference

• No references cited in the original document.