Viability and Purity Testing Service for Microbial Cell Bank Release

Overview Services Advantages FAQ

Overview

In microbial cell bank (MCB/WCB) release testing, “viability” and “purity” are two independent and equally important quality control parameters, yet they are often confused in industry practice.

Purity answers the question: “Are there any contaminants in the cell bank?” – through plate isolation, colony morphology consistency, and molecular identification to confirm the absence of non-target bacteria, yeast, or mold.
Viability answers the question: “Are the cells alive?” – through CFU (colony-forming unit) enumeration to quantify the number of live cells in the sample and assess the effectiveness of freezing and recovery.

Creative Biogene provides purity and viability testing services that align with industry practice standards, strictly distinguishing between “purity determination” and “counting assistance.” Our testing solutions can be flexibly tailored to research-grade or GMP-aligned requirements. All projects can be delivered with complete validation files and experimental reports to support your IND/BLA submission.

Creative Biogene's Services

The following core testing services cover all needs for purity and viability assessment during cell bank release. You may select individual tests or a combination based on your microbial strain type and regulatory stage.

Test Item	Target	Method Reference	Turnaround	Key Notes
Plate isolation + colony morphology consistency	Confirm pure culture, absence of non-target microbial contamination	Industry practice methods	14-22 days	Morphologically distinct colonies suggest contamination; requires molecular identification for confirmation.
CFU enumeration	Quantify viable cell count in the cell bank	Ph. Eur. 2.6.12 (counting assistance)	12-14 days	Viability indicator only, not a purity determinant; cannot detect VBNC cells.
Molecular identification (16S rDNA sequencing / MALDI-TOF MS)	Confirm target strain identity, identify non-target contaminants	In-house methods (based on ICH Q5D principles)	5-7 days	Cross-validate with morphological results; traceable to species level.

Note: Turnaround starts from sample receipt, excluding transport time. Expedited services are available based on project urgency.

Creative Biogene's Advantages

Regulatory submission support –All tests can be delivered with GLP or GMP-aligned validation files and experimental reports to support the cell substrate purity testing documentation required for IND/BLA submission. We strictly distinguish purity determination from counting assistance, avoiding incorrect citation of pharmacopoeial chapters.
In-house validation system – Medium suitability for plate isolation, statistical validity range for CFU enumeration (25-250 CFU/plate), and primer specificity for 16S rDNA sequencing are all internally validated by Creative Biogene, ensuring traceable and reproducible results.
Flexible turnaround – Standard turnaround is 2-4 weeks (depending on the test combination), with expedited options available. We provide full process progress feedback from sample receipt, through testing and data analysis, to report delivery.
One-stop cell bank services – In addition to viability and purity testing, Creative Biogene offers a complete cell bank release package including strain identification, phage detection, genetic stability studies, and adventitious agent testing – reducing the coordination burden of multiple vendors.

Need a Release Testing Plan for Your Cell Bank?

Creative Biogene's technical team will design a customized viability and purity testing strategy based on your microbial strain type, development stage, and regulatory requirements. All tests can be delivered with complete validation files and experimental reports designed to support GMP compliance and IND/BLA submission. Contact us today for detailed pricing and technical consultation.

FAQ

Q: How long does viability and purity testing take? Can it be expedited?

A: Creative Biogene's standard turnaround is 12-22 days, depending on the test combination. For example, CFU enumeration alone takes approximately 12-14 days, while the full package (plate isolation + morphology consistency + molecular identification) takes approximately 22 days. Expedited services are available, reducing turnaround by approximately 30% depending on sample type and test scope. We recommend discussing your timeline with our technical team at project initiation so we can design the most suitable schedule.

Q: How much sample do I need to provide? What if the sample volume is insufficient?

A: For viability testing (CFU enumeration), we recommend at least two independent cryovials (or equivalent liquid culture), each with a concentration of at least 1×10⁸ CFU/mL. For purity testing (plate isolation + morphology consistency), at least one cryovial or freshly activated culture is required. If the sample volume is insufficient, we can first perform a sample quality assessment to determine test feasibility. In some cases, sample amplification through additional passages may be possible, but this will extend the turnaround. We recommend contacting our technical support before sampling for guidance on the sample volume specific to your microbial strain.

Q: Does CFU enumeration detect all viable cells in a sample?

A: CFU enumeration is the traditional gold standard for viable cell counting, but it only detects culturable cells that can form colonies under the provided medium and culture conditions. Some microorganisms may enter a VBNC (viable but non-culturable) state after freezing, drying, or other environmental stresses – they remain alive but do not grow on conventional agar plates, leading to CFU counts that underestimate actual viability. Creative Biogene clearly specifies the culture medium, incubation conditions, and counting range (25-250 CFU/plate) in each viability report, and notes this limitation. If your study requires assessment of VBNC cells, we recommend combining CFU enumeration with complementary viability staining methods (e.g., Live/Dead staining).

* For research use only. Not intended for any clinical use.

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