Biomass in Bioprocessing

Bioprocessing uses living organisms to convert one or several substrate/s into a desired product. It’s used nearly everywhere today, from the environmentally-friendly production of chemical building blocks to the creation of cutting-edge pharmaceuticals like monoclonal antibodies or cell therapies.

Especially in microbial upstream bioprocessing, where microorganisms such as bacteria, fungi (such as yeast, filamentous organisms), archaea, plants, or algae are cultivated to produce a broad variety of products, biomass is the most commonly monitored bioprocess parameter. In this context it’s mainly applied to suspension cultures, where these microorganisms are grown in microtiter plates, shake flasks, serum bottles, bags, bioreactors, and other cultivation vessels.

Applicable Industries

In our experience, monitoring these kind of microbial bioprocesses is primarily found in these industrial research areas:

  • Metabolic engineering
  • Synthetic biology
  • Systems biology
  • Microbial strain / clone / candidate development, screening and characterization
  • Bioprocess development / optimization
  • Microbial fermentation

For example, we have seen
huge demand for biomass monitoring in:

FOOD
Food &
Beverage
  • Fermented Beverages
  • Animal-free food
  • Artificial meat
  • Animal feed
CHEMICALS (WHITE BIOTECH)
Chemicals
(White Biotech)
  • Flavors and fragrances
  • Cosmetics
  • Fuels
  • Chemical building blocks
  • Enzymes
BIOPHARMA
Biopharma
(Red Biotech)
  • Biopharmaceuticals
  • Diagnostics
Agriculture
Agriculture
(Green Biotech)
  • Optimized seeds
  • Biopesticides

Questions About Biomass Monitoring?

CONTACT OUR TEAM

Why Monitor Biomass?

Biomass monitoring is concerned with measuring the biomass in a culture and plotting it over time. The result is an organism- and process-specific growth curve that enables researchers to understand, optimize, and control the bioprocess and — ultimately — the production of the desired product.

Generate Microbial Growth Curves

Generate Microbial Growth Curves

Most microbial growth curves can be broken down into six distinctive growth phases:

  1. Lag Phase: The microorganisms adapt to the surrounding conditions like available nutrients, temperature or pH by adjusting their metabolism. In this phase biomass remains constant as there is no growth.

  2. Acceleration Phase: The organisms start to grow and divide, and the biomass slowly increases. In this phase, the growth rate increases.

  3. Log Phase: The organisms are now fully adapted to the surrounding conditions and grow as fast as possible. The biomass increases exponentially. Growth reaches its maximum rate and then remains constant.

  4. Deceleration Phase: When the primary nutrition source is depleted, the microorganisms cannot grow any further. The growth rate drops rapidly and the biomass increase stops. This phase can be followed by adoption to and growth on another nutrient, if available. If not, the culture will enter the next phase.

  5. Stationary Phase: Without further nutrients, the organisms stop growing. The biomass does not increase any further — the growth rate stays at zero.

  6. Death Phase: After a period of starvation, the microorganisms start to die. The biomass will decrease slowly, which results in a negative growth rate.

Monitor, Control, and Understand Your Bioprocess

cgq_shakertable_2-1

Assuming sufficient data density (number of biomass data points over time) and quality, charting the growth curves and kinetics of microbial cultures is crucial for scientists with a range of tasks and goals, including:

  • Screening for the best strain and or condition(s): When using microbial strains to create a desired product, scientists are concerned with first finding the right strain to generate it, and then with optimizing the conditions so that strain creates the highest possible concentration of the product. They will want to compare the growth curves of various strains and then of the same strain under various bioprocess conditions (such as temperature, media composition, pH, and batch vs. fed-batch).

  • Timing experimental workflows: Growth experiments often involve various steps (such as inoculation, induction, feeding, sampling, cell or product harvesting, and cooling) where the scientist needs to manually interact with the process. Knowing or, ideally, seeing which growth phase your organism is in helps with the timing of these manual work steps, and increases experimental efficiency and scientific outcome.

  • Detecting events: Among the important events that may occur during microbial fermentation are diauxic shifts, oxygen-, substrate, product or metabolite-inhibitions, and morphological changes. It’s crucial for scientists to be able to detect these events in order to characterize and optimize both the microorganism and the bioprocess.

  • Controlling the quality: Following the growth curve can help determine if an experiment is reproducible or not, and if this cultivation can be used for further experiments or production steps. It can also help scientists detect a problem — and avoid costly problems further downstream.

What can happen if you don’t monitor biomass? The biggest pain points scientists report to us are black-box bioprocesses and being “under-sampled”. Without being able to see what happens in the cultivation vessel, and without data, they have no means to screen or time manual workflows, or ensure quality control — and are at a distinct disadvantage. Monitoring biomass ensures projects run smoothly, stay within budget and deliver the expected results.

How Biomass is Measured​

  • Optical Density (OD) Measurements
  • Backscatter Measurements
  • Cell Dry Weight Measurements
  • Capacitance Measurements
Optical Density (OD) Measurements

Oldie but Goodie

Principle of Measurement: Absorbance

Light with a specific wavelength is emitted into the fermentation broth. A sensor on the other side of the broth detects the intensity of the light as it passes through. The more cells in the culture, the less light. Using the Lambert Beer law, this signal can be used to calculate the optical density, or OD.

Technologies:

Used in photometers combined with offline sampling, in plate readers, or in invasive probes for bioreactors.

  • Advantages
      • Very sensitive – can measure very low biomass concentration (usually <0.1 OD).
      • High reproducibility.
      • Easy to use.
      • Established technology with plenty of reference data.
      • Often fairly low investment costs (CAPEX) since the equipment needed already exists as standard lab infrastructure.
  • Disadvantages
      • Offline and and often invasive. Samples need to be taken, which risks contamination, interrupts the bioprocess and wastes culture volume.
      • For biomass concentrations above 0.8-1 the sample has to be diluted (adding additional manual work).
      • Discontinuous data.
      • Low data density (e.g., no data from the night or the weekends).
      • Particles can influence measurements.
      • Does not work with filamentous organisms and barely works with anaerobics.
      • Running costs for cuvettes and personnel (OPEX).
      • Requires a certain minimal culture volume to ensure enough data points.
Backscatter Measurements

MODERN APPROACH, FAST-GROWING TREND

Principle of Measurement: Backscatter

Light with a specific wavelength is emitted into the fermentation broth. A sensor close to the light source detects the amount of the light scattered back by the cells and other particles in the broth. The more cells in the culture, the more light is scattered back.

Technologies:

Used in non-invasive sensors for shake flasks and bioreactors, and in invasive probes for bioreactors.


  • Advantages
      • Automated (measurement and data handling).
      • Online and non-invasive (no samples need to be taken).
      • Good measurement range without the need for dilutions.
      • No running costs (OPEX).
      • Continuous real-time data.
      • High resolution.
      • Easy to use.
      • Works with filamentous and anaerobic organisms.
      • Applicability to a broad variety of vessel types (μL to L scale).
  • Disadvantages
      • Lower sensitivity than OD measurements.
      • Absolute values may differ due to flask-to-flask differences or experimental set-up. Only relative values can be compared directly and without calibration.
      • Scientifically proven method with reference data, but not yet as established as OD measurements.
      • Particles can influence the measurement.
      • Medium investment costs (CAPEX) for sensors and software.
Cell Dry Weight Measurements

WIDELY KNOWN BUT SLOW AND TIME-CONSUMING

Principle of Measurement: Cell Dry Weight

Scientists take a defined volume of cells from the cultivation broth and transfer it into a pre-weighed tube. The cells are then dried overnight so that any water is removed and weighed precisely. Subtracting the weight of the empty tube equals the weight of the dried cells per defined volume.

Technologies:

Offline sampling is combined with measuring the cell dry weight on a fine scale.


  • Advantages
      • Can be used whenever optical systems fail.
      • Works with any type of microorganism.
      • Often low investment costs (CAPEX) since the equipment needed (drying cabinet, exicator, and fine scale) already exist as standard lab infrastructure.
  • Disadvantages
      • Sufficient culture volume is needed for accurate weight.
      • Offline and invasive. Samples need to be taken, which bears the risk of contamination, interrupts the bioprocess and wastes culture volume.
      • Discontinuous data.
      • Low data density.
      • Slow – results take at least one day.
      • Error prone.
      • Running costs for tubes and personnel (OPEX).
Capacitance Measurements

EXPENSIVE BUT MORE THAN JUST BIOMASS

Principle of Measurement: Capacitance

Microorganisms have a cell membrane, that, if intact, can act as a capacitor when an electric field is applied. The resulting capacitance can be monitored and used to derive information about the cell concentration and the amount of cells with intact membranes — in other words, viable cells.

Technologies:

Used in invasive probes for bioreactors.


  • Advantages
      • Automated (measurement and data handling).
      • Good measurement range.
      • No running costs (OPEX).
      • Continuous real-time data.
      • High-resolution growth curves.
      • Easy to use.
      • Works with filamentous and anaerobic organisms.
      • Can be used whenever optical systems fail (e.g., OD or backscatter measurements).
      • Provides additional bioprocess data, including cell viability and media conductivity.
  • Disadvantages
      • Only applicable to bioreactors and cultivation bags.
      • High CAPEX (investment costs).
      • Measurement unit needs to be converted to a biomass unit like cell concentration or optical density.
      • Measurement results can be influenced by media, organism and bioprocess.
Optical Density (OD) Measurements
Optical Density (OD) Measurements

Oldie but Goodie

Principle of Measurement: Absorbance

Light with a specific wavelength is emitted into the fermentation broth. A sensor on the other side of the broth detects the intensity of the light as it passes through. The more cells in the culture, the less light. Using the Lambert Beer law, this signal can be used to calculate the optical density, or OD.

Technologies:

Used in photometers combined with offline sampling, in plate readers, or in invasive probes for bioreactors.

  • Advantages
      • Very sensitive – can measure very low biomass concentration (usually <0.1 OD).
      • High reproducibility.
      • Easy to use.
      • Established technology with plenty of reference data.
      • Often fairly low investment costs (CAPEX) since the equipment needed already exists as standard lab infrastructure.
  • Disadvantages
      • Offline and and often invasive. Samples need to be taken, which risks contamination, interrupts the bioprocess and wastes culture volume.
      • For biomass concentrations above 0.8-1 the sample has to be diluted (adding additional manual work).
      • Discontinuous data.
      • Low data density (e.g., no data from the night or the weekends).
      • Particles can influence measurements.
      • Does not work with filamentous organisms and barely works with anaerobics.
      • Running costs for cuvettes and personnel (OPEX).
      • Requires a certain minimal culture volume to ensure enough data points.
Backscatter Measurements
Backscatter Measurements

MODERN APPROACH, FAST-GROWING TREND

Principle of Measurement: Backscatter

Light with a specific wavelength is emitted into the fermentation broth. A sensor close to the light source detects the amount of the light scattered back by the cells and other particles in the broth. The more cells in the culture, the more light is scattered back.

Technologies:

Used in non-invasive sensors for shake flasks and bioreactors, and in invasive probes for bioreactors.


  • Advantages
      • Automated (measurement and data handling).
      • Online and non-invasive (no samples need to be taken).
      • Good measurement range without the need for dilutions.
      • No running costs (OPEX).
      • Continuous real-time data.
      • High resolution.
      • Easy to use.
      • Works with filamentous and anaerobic organisms.
      • Applicability to a broad variety of vessel types (μL to L scale).
  • Disadvantages
      • Lower sensitivity than OD measurements.
      • Absolute values may differ due to flask-to-flask differences or experimental set-up. Only relative values can be compared directly and without calibration.
      • Scientifically proven method with reference data, but not yet as established as OD measurements.
      • Particles can influence the measurement.
      • Medium investment costs (CAPEX) for sensors and software.
Cell Dry Weight Measurements
Cell Dry Weight Measurements

WIDELY KNOWN BUT SLOW AND TIME-CONSUMING

Principle of Measurement: Cell Dry Weight

Scientists take a defined volume of cells from the cultivation broth and transfer it into a pre-weighed tube. The cells are then dried overnight so that any water is removed and weighed precisely. Subtracting the weight of the empty tube equals the weight of the dried cells per defined volume.

Technologies:

Offline sampling is combined with measuring the cell dry weight on a fine scale.


  • Advantages
      • Can be used whenever optical systems fail.
      • Works with any type of microorganism.
      • Often low investment costs (CAPEX) since the equipment needed (drying cabinet, exicator, and fine scale) already exist as standard lab infrastructure.
  • Disadvantages
      • Sufficient culture volume is needed for accurate weight.
      • Offline and invasive. Samples need to be taken, which bears the risk of contamination, interrupts the bioprocess and wastes culture volume.
      • Discontinuous data.
      • Low data density.
      • Slow – results take at least one day.
      • Error prone.
      • Running costs for tubes and personnel (OPEX).
Capacitance Measurements
Capacitance Measurements

EXPENSIVE BUT MORE THAN JUST BIOMASS

Principle of Measurement: Capacitance

Microorganisms have a cell membrane, that, if intact, can act as a capacitor when an electric field is applied. The resulting capacitance can be monitored and used to derive information about the cell concentration and the amount of cells with intact membranes — in other words, viable cells.

Technologies:

Used in invasive probes for bioreactors.


  • Advantages
      • Automated (measurement and data handling).
      • Good measurement range.
      • No running costs (OPEX).
      • Continuous real-time data.
      • High-resolution growth curves.
      • Easy to use.
      • Works with filamentous and anaerobic organisms.
      • Can be used whenever optical systems fail (e.g., OD or backscatter measurements).
      • Provides additional bioprocess data, including cell viability and media conductivity.
  • Disadvantages
      • Only applicable to bioreactors and cultivation bags.
      • High CAPEX (investment costs).
      • Measurement unit needs to be converted to a biomass unit like cell concentration or optical density.
      • Measurement results can be influenced by media, organism and bioprocess.

See the sbi Way

The Comparison Guide

Finding the right biomass monitoring technology for your needs can be a challenge. To help, we leveraged nearly a decade of expertise in the field and a network of experts. First, review the 3 key factors you need to consider. Then, tap into our Biomass Monitoring Comparison Guide.

3 Factors to Consider

There are 3 key factors to consider when choosing the right biomass monitoring technology for you: your application, your cultivation vessel, and your bioprocess

APPLICATION
APPLICATION

 

Your application is closely linked to what you are actually trying to achieve.
Typical examples we’ve seen among our customers include:

  • More Details
      • Strain development, screening and characterization.

      • Bioprocess optimization.

      • Media optimization.

      • Growth characterization (including toxicity tests, substrate-/product-inhibitions, and oxygen-limitations).

      • Timing of workflows (such as inoculation, induction, sampling, feeding, or harvesting).

      • Product characterization.

      • Scale up.

      • Quality control.

Bioprocess
Bioprocess

 

The same application will differ from project to project — often because of the bioprocess used. To find the most suitable technology, ask these questions:

  • More Details
      • How many strains in parallel do we need to monitor?

      • How much culture volume do we need for product characterization, for instance?

      • How many resources for manual work steps are available?

      • How sensitive does the measurement need to be?

      • Which measurement range do we need to cover?

      • What level of data resolution do we need?

      • What organism are we using?

Cultivation Vessel
Cultivation Vessel

 

The combination of application and these bioprocess details will lead to your choice of cultivation vessel. In our experience, the most common include:

  • More Details
      • Titer- or Micro-titer plates (MTPs).

      • Shake flasks (and serum bottles).

      • Benchtop bioreactors.

Our Biomass Monitoring
Comparison Guide

Although most scientists are well aware of these factors, we saw that there was no tool available to compare and decide on the best biomass monitoring technology. We created the first Biomass Monitoring Comparison Guide as a scientist’s comparison tool for the three most common vessel types.

Overview Table

Legend

DisadvantageousScore 1
Disadvantageous
Average / AcceptableScore 2
Average / Acceptable
BeneficialScore 3
Beneficial
SBI Rating
Vessel Technology Principle of Measurement Overall Manual hands-on-time needed Measurement Data Bioprocess Cost
Microtiter Plates
Microtiter
Plate Reader incl. incubation Backscatter Beneficial Beneficial Beneficial Beneficial Beneficial Disadvantageous
Plate Reader excl. incubation Absorbance Average / Acceptable Beneficial Beneficial Average / Acceptable Beneficial Average / Acceptable
Plate Reader incl. incubation Image Analysis Average / Acceptable Beneficial Beneficial Average / Acceptable Beneficial Disadvantageous
Shake Flasks & Serum Bottles
Vessle
Non-invasive Sensor Backscatter Beneficial Beneficial Average / Acceptable Beneficial Beneficial Beneficial
Sampling + Fine Scale Cell Dry Weight Average / Acceptable Disadvantageous Average / Acceptable Disadvantageous Disadvantageous Beneficial
Sampling + Photometer Absorbance Average / Acceptable Disadvantageous Average / Acceptable Average / Acceptable Disadvantageous Beneficial
Bioreactor
Vessle
Non-invasive Sensor Backscatter Beneficial Beneficial Beneficial Average / Acceptable Beneficial Beneficial
Invasive Probe Capacitance Average / Acceptable Beneficial Beneficial Beneficial Average / Acceptable Average / Acceptable
Invasive Probe Backscatter Average / Acceptable Beneficial Beneficial Average / Acceptable Average / Acceptable Beneficial
Invasive Probe Absorbance Average / Acceptable Beneficial Average / Acceptable Beneficial Average / Acceptable Beneficial
Sampling + Fine Scale Cell Dry Weight Average / Acceptable Disadvantageous Beneficial Disadvantageous Average / Acceptable Beneficial
Sampling + Photometer Absorbance Average / Acceptable Disadvantageous Average / Acceptable Average / Acceptable Average / Acceptable Beneficial
Vessel Microtiter Plates
Technology Plate Reader incl. incubation Plate Reader excl. incubation Plate Reader incl. incubation
Principle of Measurement Backscatter Absorbance Image Analysis
Overall Beneficial Average / Acceptable Average / Acceptable
Manual hands-on-time needed Beneficial Beneficial Beneficial
Measurement Beneficial Beneficial Beneficial
Data Beneficial Average / Acceptable Average / Acceptable
Bioprocess Beneficial Beneficial Beneficial
Cost Disadvantageous Average / Acceptable Disadvantageous
Vessel Shake Flasks & Serum Bottles
Technology Non-invasive Sensor Sampling + Fine Scale Sampling + Photometer
Principle of Measurement Backscatter Cell Dry Weight Absorbance
Overall Beneficial Average / Acceptable Average / Acceptable
Manual hands-on-time needed Beneficial Disadvantageous Disadvantageous
Measurement Average / Acceptable Average / Acceptable Average / Acceptable
Data Beneficial Disadvantageous Average / Acceptable
Bioprocess Beneficial Disadvantageous Disadvantageous
Cost Beneficial Beneficial Beneficial
Vessel Bioreactor
Technology Non-invasive Sensor Invasive Probe Sampling + Fine Scale Sampling + Photometer
Principle of Measurement Backscatter Capacitance Backscatter Absorbance Cell Dry Weight Absorbance
Overall Beneficial Average / Acceptable Average / Acceptable Average / Acceptable Average / Acceptable Average / Acceptable
Manual hands-on-time needed Beneficial Beneficial Beneficial Beneficial Disadvantageous Disadvantageous
Measurement Beneficial Beneficial Beneficial Average / Acceptable Beneficial Average / Acceptable
Data Average / Acceptable Beneficial Average / Acceptable Beneficial Disadvantageous Average / Acceptable
Bioprocess Beneficial Average / Acceptable Average / Acceptable Average / Acceptable Average / Acceptable Average / Acceptable
Cost Beneficial Average / Acceptable Beneficial Beneficial Beneficial Beneficial

We rated each technology using 20 different criteria, and covering factors such as bioprocess, data and budget. We also evaluated each technology across each type of vessel.

This Guide Allows You to:​

  • Compare different technologies for each criterium.

  • Identify the best-fit technology for the category most relevant for your situation.

  • Compare all existing technologies across each type of vessel.

In the full comparison guide, you can see the definitions of all categories and criteria, incl the individual scores for each technology.

Download the Full Ebook
Biomass Monitoring - Find the Best Fit for Your Bioprocess With This 360° View on Available Technologies

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sbi's Biomass Monitoring Solutions

Scientific Bioprocessing (SBI) is dedicated to pioneering Digitally Simplified Bioprocessing. We develop cutting-edge digital technologies (e.g., sensors, actuators and software) that simplify bioprocessing activities from the lab to the production floor.

 

Our biomass monitoring solutions feature sensors and software that:

  • Generate high-resolution growth curves in real time to provide you with actionable insights.

  • Save you hours of manual, hands-on time required for alternative offline approaches.

  • Enable you to use nights or weekends for growth experiments.

 

We enable you to simply press “start” in our software — and automatically receive high quality biomass data in real-time that you can trust and use to accelerate your research.

Our Biomass Monitoring Solutions

CGQ_Shake_Flask_above

CGQ

For Shake Flasks & Serum Bottles

  • Measure biomass online and non-invasively through the glass wall of the flask.

  • Monitor up to 64 flasks in parallel.

Compatible with:

  • A broad range of microorganisms (such as bacteria, yeast, anaerobics, and thermophile or filamentous organisms).

  • All shake flask sizes (100 mL – 5000 mL).

  • All incubation shakers (clamps and sticky mats).

biomass_monitoring_bioreactor_bior

CGQ BioR

For Bioreactors

  • Measure biomass online and non-invasively through the glass wall of the bioreactor.

  • Two measurement modes for high and low biomass concentrations.

Compatible with:

  • A broad variety of microorganisms (such as bacteria, yeast, anaerobic, thermophile, or filamentous organisms).

  • All bioreactor types (single- and double-jacket) sizes.

SBI-Laptop-biomass-based-feeding-shot

DOTS Software

For Monitoring & Analytics

  • Powerful software for easy sensor handling and real-time data visualization.

  • Reduce your sensor setup time by using pre-defined application templates.
  • Gain actionable insights into your bioprocess.
  • Benefit from effortless data visualization and analysis of Critical Process Parameters in real-time.

Interested in Backscatter-based Technologies for Biomass Monitoring? 

Speak With An Expert

View The Success Stories

SBI-Success-Table
"The CGQ provided accurate growth curves with very dense sampling intervals and gave us the opportunity to identify differenes in growth behaviors."

-- Prof. Dr. Lars Blank (RWTH Aachen)
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SBI-Success-Table
"The backscatter data we gathered here with the CGQ system clearly shows a match with another growth characterisation parameter, in this case with the oxygen transfer rate (OTR)."

-- Frédéric Lapierre (HS München)
HM
SBI-Success-Table
"The CGQ BioR system provides precise growth curves with a very dense sampling interval, freeing my team for tasks with higher added value"

-- Prof. Dr. Lars Blank (RWTH Aachen)
Technical University Dresden)
BioR Graph
"The CGQ BioR is well suited for monitoring biomass of cultivations with thermophilic organisms that require high temperatures and long fermentation times."

-- Dipl. Ing. Robert Klausser (Integrated Bioprocess Development, TU Wien)
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