AN-NIR-093
2021-05
Quality Control of fermentation processes
Multiparameter determination within one minute
Summary
The production of biofuels from renewable feedstock has grown immensely in the past several years. Bioethanol is one of the most interesting alternatives for fossil fuels, since it can be produced from raw materials rich in sugars and starch. Ethanol fermentation is one of the oldest and most important fermentation processes used in the biotechnology industry. Although the process is well-known, there is a great potential for its improvement and a proportional reduction in production costs. Due to the seasonal variation of feedstock quality, ethanol producers to need to monitor the fermentation process to ensure the same quality product is achieved.
Near-infrared spectroscopy (NIRS) offers rapid and reliable prediction of ethanol content, sugars, Brix, lactic acid, pH, and total solids at any stage of the fermentation process.
Result
All 206 measured Vis-NIR spectra (Figure 2) were used to create a prediction model for quantification of the key fermentation parameters. The quality of the prediction model was evaluated using correlation diagrams, which display a very high correlation between the Vis-NIR prediction and the reference values. The respective figures of merit (FOM) display the expected precision of a prediction during routine analysis.
Result ethanol content
Figures of merit |
Value |
---|---|
R2 | 0.998 |
Standard error of calibration |
0.21% |
Standard error of cross-validation | 0.22% |
Result solid content
Figures of merit |
Value |
---|---|
R2 | 0.982 |
Standard error of calibration |
0.87% |
Standard error of cross-validation |
1.06% |
Result brix index
Figures of merit |
Value |
---|---|
R2 | 0.987 |
Standard error of calibration |
0.66 |
Standard error of cross-validation |
0.87 |
Result total sugar content
Figures of merit |
Value |
---|---|
R2 | 0.981 |
Standard error of calibration |
1.09% |
Standard error of cross-validation |
1.30% |
Result glucose content
Figures of merit |
Value |
---|---|
R2 | 0.920 |
Standard error of calibration |
0.70% |
Standard error of cross-validation |
0.86% |
Result lactic acid content
Figures of merit |
Value |
---|---|
R2 | 0.722 |
Standard error of calibration |
0.09% |
Standard error of cross-validation |
0.10% |
Result pH value
Figures of merit |
Value |
---|---|
R2 | 0.734 |
Standard error of calibration |
0.17 |
Standard error of cross-validation |
0.19 |
Result maltotriose content
Figures of merit |
Value |
---|---|
R2 | 0.928 |
Standard error of calibration |
0.36% |
Standard error of cross-validation |
0.42% |
Result dextrin content
Figures of merit | Value |
---|---|
R2 | 0.964 |
Standard error of calibration | 0.60% |
Standard error of cross-validation | 0.68% |
Conclusion
This application note demonstrates the feasibility to determine multiple key parameters of the fermentation process with NIR spectroscopy. Corn fermentation is a well-established process which typically runs for 55–60 hours. Samples are extracted from fermenters every few hours and sent to the laboratory for analytical measurement. Several analytical methods need to be used to monitor key quality parameters for the fermentation process. Vis-NIR spectroscopy enables a fast alternative with high accuracy, and therefore represents a suitable single method to monitor the fermentation process.
Parameter | Method | Time to result |
---|---|---|
Ethanol, sugars | HPLC | ∼30–45 min |
Brix index | Refractometer | ∼3–5 min |
pH | pH meter | ∼3–5 min |
Solids | LOD Balance | ∼10–15 min |