Fiber-Optic Probe for Bioreactor Optical Density Monitoring

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Solution Overview

Problem

Existing fiber-optic probes face challenges in measuring high optical density levels and biomass concentration accurately, particularly in biological growth media, as they often exhibit non-linear responses above 50 optical density units, which limits their effectiveness in monitoring fermentation processes.

Innovation Solution

A fiber-optic probe system that uses optical fibers partitioned by a transparent window with radially and circumferentially spaced ends and converging longitudinal projections, allowing for in situ measurement of light intensity in biological reactors, providing a more linear response across a wide range of optical densities from 50 to 200 units.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional fiber-optic probes are used for in situ measurement, then the measurement process is simplified and real-time monitoring is enabled, but the measurement precision deteriorates at high optical density levels (above 50 OD units) due to non-linear response

Engineering Contradiction:

Improvereal-time monitoring capabilityVSAvoidmeasurement linearity at high optical density

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The probe divides the light measurement function into separate segments: one optical fiber directs light into the medium while another measures reflected light. This segmentation allows independent optimization of each fiber's properties and positioning, enabling the measurement system to maintain linearity across high optical density ranges by separating the illumination and detection paths

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A transparent window is introduced as an intermediary element between the optical fibers and the biological medium. This window provides a stable, optically clear interface that allows light to pass through while enabling the fibers to remain positioned optimally for measurement, thereby maintaining measurement precision without compromising real-time monitoring capability

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If off-line optical density analysis is used, then measurement precision is maintained through calibration, but the productivity decreases due to time-consuming sampling and analysis processes

Engineering Contradiction:

Improveaccuracy of cell concentration measurementVSAvoidfermentation process efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The fiber-optic probe enables the system to perform its own measurement function in situ without requiring external sampling equipment or manual intervention. The probe continuously monitors optical density directly in the fermentation medium, eliminating the need for separate sampling, dilution, and analysis steps while maintaining measurement accuracy through its optimized optical geometry

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The mechanical sampling and analysis system is replaced with an optical measurement system. Instead of physically removing samples for analysis, the probe uses light interaction with the medium to determine cell concentration, thereby maintaining measurement precision while dramatically improving fermentation process productivity through continuous real-time monitoring

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables accurate and reproducible cell concentration measurements in bioreactors, reducing variability and enabling real-time monitoring and control of fermentation processes, including bacterial and yeast cultures, by providing precise feedback on biomass and growth rates for optimal nutrient feeding.

Implementation Method 1

This probe can be used for in situ detection and measurement of the intensity of light scattered by particles suspended in a transparent or translucent fluid medium

Methodology Applied

Scientific EffectLight scattering: Scattering

Implementation Method 2

measuring the intensity of light reflected from the illuminated fluid media by way of one or more optical fibers

Methodology Applied

Scientific EffectOptical reflection: Reflection

Data Source

PatentUS7745167B2Fiber-optic probes and methods of measuring biological materials

Publication Date: 2010.06.29 PFENEX INC

AI summary

A method for monitoring fluid media, such as a dynamic biological system, in a biological reactor containing developing culture fluid media. The method includes the step of directing light into the fluid media by way of one or more optical fibers to produce an illuminated fluid media and then measuring the intensity of light reflected from the illuminated fluid media by way of one or more optical fibers, the optical fibers being partitioned from the fluid media by a transparent window having inner and outer surfaces; the fibers having ends terminating adjacent to and confronting the inner surface of the window and extending in a direction away from the window, the corresponding ends of the fibers being radially and circumferentially spaced from one another, the corresponding ends of the fibers having converging and intersecting longitudinal projections therefrom, the intersecting longitudinal projections from the fibers being entirely within the window. Additionally, a fiber-optic probe is discussed.