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pH – must be kept stable (typically 5.0–6.0) using lime (CaCO₃/Ca(OH)₂) or H₂SO₄Temperature – optimum around 35–38°C for most lactic acid bacteriaDissolved Oxygen (DO) – fermentation is mostly anaerobic but DO dynamics still indicate cell activityAgitation – ensures homogeneous conditionsSugar concentration – influences osmotic pressure and final acid yieldCell growth profile – correlates with sugar consumption and acid formationLactate Yield (%)Final Lactate Concentration (g/L)Batch Time & ProductivityVariability between batches
NIR / Raman spectroscopyMeasures molecular absorbance patternsTracks sugar , lactic acid, and other chemical component pH probeDO sensorTemperature sensorOff-gas (CO₂) analyser
NIR is a light-based analytical technique that measures how materials absorb near-infrared light (700–2500 nm).Different chemical bonds absorb NIR light differently, creating a “spectral fingerprint.”Raman measures how molecules scatter laser light. When a laser hits a molecule, the vibration of its chemical bonds causes a unique scattering pattern → the Raman spectrum.
Extract useful information from complex spectraDetect abnormal batchesIdentify root causesPredict product quality (lactic acid concentration)Reduce lab testingSupport real-time process optimisation
Visualise batch similarity/differencesDetect abnormal or drifting batchesUnderstand which variables drive variationMonitor fermentation stabilityIdentify contamination or sensor driftScore plot → how batches differLoading plot → which variables cause the differenceT² and Q-residuals → abnormality indicators
X = spectra, process variables, sensor signalsY = final lactic acid concentration, yield, purity, etc.Predict lactic acid concentration from NIR/RamanPredict yield before batch endsModel relationships between process variables and qualityReduce lab samples (real-time quality prediction)Understand which variables are most importantPredicted vs actual qualityRegression coefficientsVIP scores (variable importance)Latent variables explaining chemistry + process behaviour
Theory Summary: Chemometrics & Lactic Acid Fermentation
A foundational page for the Fermentation Insight Hub portfolio
🔬 1. Lactic Acid Fermentation — Scientific Background
Lactic acid is produced via microbial fermentation where microorganisms convert sugar (typically glucose or sucrose) into lactic acid under controlled conditions.
Lactic Acid-Producing Bacteria (LAB) and Their Fermentative Pathway
Catabolic pathways of glucose fermentation by lactic acid-producing bacteria (LAB) [1]
(A): homofermentation in Lactococcus lactis or Lactobacillus acidophilus,
(B): mixed acid fermentation tococcus lactis), and
(C): heterofermentation in Lactobacillus casei.
Simple Process Flow of Fermentation [1,2]
Key process parameters influencing fermentation:
These factors drive:
🧪 2. Process Analytical Technology (PAT)
PAT refers to real-time monitoring tools that allow continuous measurement of critical process variables.
Typical PAT sensors used in fermentation:
PAT produces high-dimensional, multivariate data — ideal for chemometrics.
[3]
NIR (Near-Infrared) and Raman spectroscopy
NIR of L-Lactic Acid [4]
Chemometrics + PCA/PLS
Chemometrics is the use of mathematics and statistics to analyse chemical or bioprocess data.
In fermentation, sensors (NIR, Raman, pH, DO, temperature) generate complex, high-dimensional, noisy data.
Chemometrics helps make sense of it.
Chemometrics helps you:
PCA — Principal Component Analysis
PCA is a chemometric technique that reduces multivariate data (like spectra or sensor readings) into a few summary components called principal components.
PCA helps you:
PCA outputs:
[5]
PLS — Partial Least Squares Regression
PLS relates (X) → (Y):
PLS helps you:
PLS outputs:
In simple words:
👉 PLS predicts product quality using process/spectral data.
PCA = monitoring & understanding
PLS = prediction & quality modelling
References
[1] Lactic Acid: A Comprehensive Review of Production to Purification, no date.
[2] Life Cycle Impact Assessment of Polylactic Acid (PLA) Produced from Sugarcane in Thailand, no date.
[3] Endress+Hauser, “Process Analytical Technology in Life Sciences.” Available: .
[4] Application of Near-Infrared Spectroscopy Technology in the Complex Fermentation System to Achieve High-Efficiency Production, no date.
[5] JASCO Inc., “Chemometrics – FTIR Microscopy.” Available: .
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